Aerosol provision systems with liquid amount estimation via features of the aerosol provision system

Abstract

Aerosol provision system (10) comprising a reservoir (3) holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser (7) for vaporising liquid from the reservoir; and a controller (28) configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value and a puff duration value, and using an equation relating power level and puff duration to mass of aerosol for a specified aerosol provision system vaporising liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir; wherein a feature of the aerosol provision system is modified compared to the specified aerosol provision system to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

Description

[0001] AEROSOL PROVISION SYSTEMS WITH LIQUID AMOUNT ESTIMATION VIA FEATURES OF THE AEROSOL PROVISION SYSTEM

[0002] Technical Field

[0003] The present disclosure relates to aerosol provision systems configured to estimate an amount of liquid in a reservoir of the aerosol provision system, via one or more features of the aerosol provision system, and methods for estimating a liquid amount in an aerosol provision system.

[0004] Background

[0005] Aerosol provision systems which deliver aerosol for inhalation by a user are known, and include e-cigarettes and other electronic nicotine delivery systems that deliver nicotine in the aerosol. In some systems, the aerosol is generated by vaporising liquid to form a vapour, which is entrained in a flow of air drawn through the system as a user inhales or “puffs” on a mouthpiece of the system. Vaporisation is often produced by heating the liquid with an electrically powered heater comprising one or more heating elements; these and similar arrangements can be referred to as a vaporiser. The liquid is stored in a tank or reservoir of the system, and delivered to the vaporiser at a suitable rate in order to be vaporised. For example, this may be achieved by a porous wick which establishes a liquid flow path between the interior of the reservoir and the heater.

[0006] The user can continue to use the aerosol provision system for as long as there is liquid available in the reservoir. When the liquid has been consumed, no more aerosol can be generated and, depending on the design of the system, the user has to replace the whole system, replace the reservoir with a new full reservoir, replace a cartridge part of the system that includes the reservoir and possibly the vaporiser with a new cartridge having a full reservoir, or refill the reservoir with more liquid from a separate store. It is useful if the user is able to monitor the consumption of the liquid, for example to keep track of their usage of the aerosol provision system, and also to be aware when the reservoir is becoming empty so that preparation can be made for any of the above actions for obtaining a new supply of liquid. A range of options have been suggested for this, including a reservoir with a transparent wall through which the user can directly observe the amount of remaining liquid, and a variety of sensors that are configured to measure or detect the level of liquid in the reservoir. These approaches require particular features of or directly associated with the reservoir, however, which may need to be replaced together with the reservoir in systems having a replaceable cartridge.

[0007] Approaches for determining an amount of liquid in the reservoir of an aerosol provision system therefore of interest. Summary

[0008] According to a first aspect of some embodiments described herein, there is provided an aerosol provision system comprising: a reservoir holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for a specified aerosol provision system vaporising liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein a feature of the aerosol provision system is modified compared to the specified aerosol provision system to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

[0009] According to a second aspect of some embodiments described herein, there is provided an aerosol provision system comprising: a reservoir holding an initial volume of liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system with a same type of vaporiser and a reservoir holding a specified initial volume of liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the initial volume of the liquid of the first type in the reservoir is modified compared to the specified initial volume to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

[0010] According to a third aspect of some embodiments described herein, there is provided a method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for a specified aerosol provision system vaporising liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein a feature of the aerosol provision system has been modified compared to the specified aerosol provision system to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

[0011] According to a fourth aspect of some embodiments described herein, there is provided a method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding an initial volume of liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system or cartridge therefor with a same type of vaporiser and a reservoir holding a specified initial volume of liquid of a specified liquid type different from the first liquid type; and estimating an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the initial volume of the liquid of the first type in the reservoir has been modified compared to the specified initial volume in order to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

[0012] According to a fifth aspect of some embodiments described herein, there is provided an aerosol provision system comprising: a reservoir holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system with a same type of vaporiser and with liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein a composition of the first liquid type is modified compared to the specified liquid type such that the first liquid type has a same vaporisation behaviour as the specified liquid type.

[0013] According to a sixth aspect of some embodiments described herein, there is provided A method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system or cartridge therefor with a same type of vaporiser and with liquid of a specified liquid type different from the first liquid type; and estimating an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the first liquid type has a composition which is modified compared to the specified liquid type such that the first liquid type has a same vaporisation behaviour as the specified liquid type.

[0014] According to a seventh aspect of some embodiments described herein, there is provided an aerosol provision system comprising: a reservoir holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system with a specified configuration of vaporiser and with liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the vaporiser is modified compared to the specified configuration in order to deliver a different amount of heat energy for vaporising the liquid from the level of power supplied and thereby compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

[0015] According to an eighth aspect of some embodiments described herein, there is provided a method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system or cartridge therefor with a specified configuration of vaporiser and with liquid of a specified liquid type different from the first liquid type; and estimating an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the vaporiser has been modified compared to the specified configuration in order to deliver a different amount of heat energy for vaporising the liquid from the level of power supplied and thereby compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

[0016] According to a ninth aspect of some embodiments described herein, there is provided an aerosol provision system comprising: a reservoir holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; the vaporiser located in an air flow path; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system with a vaporiser located in a specified configuration of air flow path and with liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the air flow path is modified compared to the specified configuration in order to provide a different air flow past the vaporiser and thereby compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

[0017] According to a tenth aspect of some embodiments described herein, there is provided a method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser located in an air flow path and configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system or cartridge therefor with a vaporiser located in a specified configuration of air flow path and with liquid of a specified liquid type different from the first liquid type; and estimating an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the air flow path has been modified compared to the specified configuration in order to provide a different air flow past the vaporiser and thereby compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

[0018] These and further aspects of the certain embodiments are set out in the appended independent and dependent claims. It will be appreciated that features of the dependent claims may be combined with each other and features of the independent claims in combinations other than those explicitly set out in the claims. Furthermore, the approach described herein is not restricted to specific embodiments such as set out below, but includes and contemplates any appropriate combinations of features presented herein. For example, an aerosol provision system and a method may be provided in accordance with approaches described herein which includes any one or more of the various features described below as appropriate.

[0019] Brief Description of the Drawings

[0020] Various embodiments of the invention will now be described in detail by way of example only with reference to the following drawings in which:

[0021] Figure 1 shows a simplified schematic longitudinal cross-section through an example aerosol provision system to which aspects of the disclosure can be applied;

[0022] Figure 2 shows a graph of aerosol collected mass measurements against puff duration for a range of vaporiser power levels collected from a population of aerosol provision systems with a same type of vaporiser;

[0023] Figure 3 shows the graph of Figure 2 with linear best fit lines added for each vaporiser power level;

[0024] Figure 4 shows the graph of Figure 2 with nonlinear best fit lines added for each vaporiser power level;

[0025] Figure 5 shows a simplified longitudinal cross-section through an aerosol provision system configured according to examples of an aspect of the present disclosure;

[0026] Figure 6 shows simplified schematic depictions of reservoirs for aerosol provision systems containing with different initial volumes of different types of liquid in order to compensate for differences in vaporisation behaviour between different liquid types, according to an example of the present disclosure;

[0027] Figure 7 shows simplified schematic depictions of reservoirs for aerosol provisions systems having different capacities and filled with different initial volumes of different types of liquid in order to compensate for differences in vaporisation behaviour between different liquid types, according to another example of the present disclosure;

[0028] Figure 8 shows a flow chart of steps in a first example method for estimating liquid amount in an aerosol provision system according to an aspect of the present disclosure;

[0029] Figure 9 shows a flow chart of steps in a second example method for estimating liquid amount in an aerosol provision system according to an aspect of the present disclosure.

[0030] Figure 10 shows a flow chart of steps in a third example method for estimating liquid amount in an aerosol provision system according to an aspect of the present disclosure;

[0031] Figures 11 A-11 D show simplified schematic side views of example vaporisers having the form of wire coils and having differing coil structures in order to provide modifications to the vaporisers according to an example of the present disclosure; Figures 12A-12D show simplified schematic side views of example vaporisers having distinct electrical connections of differing configuration in order to provide modifications to the vaporisers according to another example of the present disclosure;

[0032] Figures 13A and 13B show simplified schematic side views of example vaporisers having distinct electrical connections with differing resistive elements in order to provide modifications to the vaporisers according to still another example of the present disclosure;

[0033] Figures 14A and 14B shows simplified schematic plan views of example vaporisers having differing porous structures in order to provide modifications to the vaporisers according to a further example of the present disclosure;

[0034] Figure 15 shows a flow chart of steps in a fourth example method for estimating liquid amount in an aerosol provision system according to an aspect of the present disclosure

[0035] Figure 16 shows a simplified schematic cross-sectional side view of an example aerosol provision system with an airflow path that can be modified in accordance with aspects of the present disclosure;

[0036] Figures 17A-17C show simplified schematic cross-sectional side views of example air flow paths of differing configuration for altering air flow velocity to provide modifications to the air flow paths according to examples of the present disclosure;

[0037] Figure 18 shows a simplified schematic cross-sectional side view of an example air flow path having an alternative modification for altering air flow velocity according to another example of the present disclosure;

[0038] Figures 19A-19C shows simplified schematic cross-sectional side views of example air flow paths of differing configuration for altering air flow volume to provide modifications to the air flow paths according to a further example of the present disclosure;

[0039] Figure 20 shows a simplified schematic cross-sectional side view of an example air flow path having a modification for providing turbulent air flow according to another example of the present disclosure; and

[0040] Figure 21 shows a flow chart of steps in a fifth example method for estimating liquid amount in an aerosol provision system according to an aspect of the present disclosure.

[0041] Detailed Description

[0042] Aspects and features of certain examples and embodiments are discussed I described herein. Some aspects and features of certain examples and embodiments may be implemented conventionally and these are not discussed I described in detail in the interests of brevity. It will thus be appreciated that aspects and features of apparatus and method discussed herein which are not described in detail may be implemented in accordance with any conventional techniques for implementing such aspects and features.

[0043] As described above, the present disclosure relates to electronic aerosol or vapour provision systems, such as e-cigarettes. Throughout the following description the terms “e- cigarette” and “electronic cigarette” may sometimes be used; however, it will be appreciated these terms may be used interchangeably with aerosol (vapour) provision system or device. The systems are intended to generate an inhalable aerosol by vaporisation of an aerosolforming substrate in the form of a liquid or gel which may or may not contain nicotine. Additionally, hybrid systems may comprise a liquid or gel substrate plus a solid substrate which is also heated. The solid substrate may be for example tobacco or other non-tobacco products, which may or may not contain nicotine. The term “aerosolisable substrate material” as used herein is intended to refer to substrate materials which can form an aerosol, either through the application of heat or some other means. The term “aerosol” may be used interchangeably with “vapour”.

[0044] As used herein, the term “component” is used to refer to a part, section, unit, module, assembly or similar of an electronic cigarette or similar device that incorporates several smaller parts or elements, possibly within an exterior housing or wall. An electronic cigarette may be formed or built from one or more such components, and the components may be removably or separably connectable to one another, or may be permanently joined together during manufacture to define the whole electronic cigarette. For example, a system may comprise (at least) two components separably connectable to one another and configured, for example, as an aerosolisable substrate material carrying component holding liquid or another aerosolisable substrate material (a cartridge, cartomiser or consumable, or simply “pod”), and a control unit or device (“device”) component having a controller for controlling operation of the aerosol provision system, and a battery for providing electrical power to operate an element for generating vapour from the substrate material. For the sake of providing a concrete example, in the present disclosure, a cartridge or cartomiser (cartridge component or consumable) is described as an example of the aerosolisable substrate material carrying portion or component in which the aerosolisable substrate material is a liquid or a gel held in a reservoir or tank (storage area), but the disclosure is not limited in this regard and is applicable to any configuration of aerosol provision system having a liquid reservoir. A cartridge component may include more or fewer parts than those included in the examples. This is true also of the device component.

[0045] The present disclosure is particularly relevant to aerosol provision systems and components thereof that utilise aerosolisable substrate material in the form of a liquid or a gel which is held in a reservoir, tank, container or other receptacle comprised in the system. In such systems an arrangement for delivering the substrate material from the reservoir for the purpose of providing it for vapour I aerosol generation is included. The terms “liquid”, “gel”, “fluid”, “source liquid”, “source gel”, “source fluid” and the like may be used interchangeably with “aerosolisable substrate material” and “substrate material” to refer to aerosolisable substrate material that has a form capable of being stored and delivered in accordance with examples of the present disclosure.

[0046] Figure 1 is a highly schematic diagram (not to scale) of a generic example aerosol / vapour provision system such as an e-cigarette 10, presented for the purpose of showing the relationship between the various parts of a typical system and explaining the general principles of operation. The e-cigarette 10 has a generally elongate shape in this example, extending along a longitudinal axis indicated by a dashed line, and comprises two main components, namely a control or power component, section or unit (device component) 20, and a cartridge component, assembly or section 30 (sometimes referred to as a cartomiser or clearomiser) carrying aerosolisable substrate material and operating as a vapourgenerating component.

[0047] The cartridge component 30 includes a reservoir 3 containing a source liquid or other aerosolisable substrate material comprising a formulation such as liquid or gel from which an aerosol is to be generated, for example containing nicotine. As an example, the source liquid may comprise around 1 to 3% nicotine and 50% glycerol, with the remainder comprising roughly equal measures of water and propylene glycol, and possibly also comprising other components, such as flavourings. Nicotine-free source liquid may also be used, such as to deliver flavouring. A solid substrate (not illustrated), such as a portion of tobacco or other flavour element through which vapour generated from the liquid is passed, may also be included. The reservoir 3 has the form of a storage tank, being a container or receptacle in which source liquid can be stored such that the liquid is free to move and flow within the confines of the tank. For a consumable cartridge component 30, the reservoir 3 may be sealed after filling during manufacture so as to be disposable after the source liquid is consumed, otherwise, it may have an inlet port or other opening through which new source liquid can be added by the user. The cartridge component 30 also comprises an electrically powered heating element or heater 4 located externally of the reservoir tank 3 for generating the aerosol by vaporisation of the source liquid by heating. Note that in other examples, source liquid may be generated by an alternative powered means such as a vibrating mesh. More generally, the powered means that vaporise the liquid may be referred to as a vapour generating element or vaporiser. A liquid transfer or delivery arrangement (liquid transport element) such as a wick or other porous element 6 may be provided to deliver source liquid from the reservoir 3 to the heater 4 or other vapour generator. A wick 6 may have one or more parts located inside the reservoir 3, or otherwise be in fluid communication with the liquid in the reservoir 3, so as to be able to absorb source liquid and transfer it by wicking or capillary action to other parts of the wick 6 that are adjacent or in contact with the heater 4. This liquid is thereby heated and vaporised, to be replaced by new source liquid from the reservoir for transfer to the heater 4 by the wick 6. The wick may be thought of as a bridge, path or conduit between the reservoir 3 and the heater 4 that delivers or transfers liquid from the reservoir to the heater. Terms including conduit, liquid conduit, liquid transfer path, liquid delivery path, liquid transfer mechanism or element, and liquid delivery mechanism or element may all be used interchangeably herein to refer to a wick or corresponding component or structure.

[0048] A heater and wick (or similar) combination is sometimes referred to as an atomiser or atomiser assembly 7, and the reservoir 3 with its source liquid plus the atomiser 7 may be collectively referred to as an aerosol source. Other terminology may include a liquid delivery assembly or a liquid transfer assembly, where in the present context these terms may be used interchangeably to refer to a vapour-generating element (vapour generator) plus a wicking or similar component or structure (liquid transport element) that delivers or transfers liquid obtained from a reservoir to the vapour generator for vapour I aerosol generation. Various designs are possible, in which the parts may be differently arranged compared with the highly schematic representation of Figure 1. For example, the wick 6 may be an entirely separate element from the heater 4, or the heater 4 may be configured to be porous and able to perform at least part of the wicking function directly (a conductive mesh, such as a metallic mesh, for example). In an electrical or electronic device, the vapour generating element may be an electrical heating element that operates by ohmic / resistive (Joule) heating or by inductive heating. In general, therefore, an atomiser can be considered as one or more elements that implement the functionality of a vapour-generating or vaporising element able to generate vapour from source liquid delivered to it, and a liquid transport or delivery element able to deliver or transport liquid from a reservoir or similar liquid store to the vapour generator by a wicking action I capillary force. An atomiser is typically housed in a cartridge component of an aerosol generating system. In some designs, liquid may be dispensed from a reservoir directly onto a vapour generator with no need for a distinct wicking or capillary element. Embodiments of the disclosure are applicable to all and any such configurations which are consistent with the examples and description herein.

[0049] Returning to Figure 1 , the cartridge component 30 also includes a mouthpiece or mouthpiece portion 35 having an opening or aerosol outlet through which a user may inhale the aerosol generated by the atomiser 7. A single inhalation, during which the user obtains an amount of aerosol, will be referred to herein as a “puff”. In other designs, a mouthpiece may be provided as a separate component which may be permanently or separably connectable to the cartridge component 30.

[0050] The power component or control unit or, simply, device or device component 20 includes a cell or battery 5 (referred to hereinafter as a battery, and which may be rechargeable) to provide power for electrical components of the e-cigarette 10, in particular to operate the vaporiser such as the heater 4. Additionally, there is a controller 28 such as a printed circuit board and / or other electronics or circuitry for generally controlling the e- cigarette. The control electronics / circuitry 28 operates the heater 4 using power from the battery 5 when vapour is required, for example in response to a signal from an air pressure sensor or air flow sensor (“puff sensor”, not shown) that detects an inhalation on the system 10 during which air enters through one or more air inlets 26 in the wall of the device component 20. When the heater 4 is operated, the heater 4 vaporises source liquid delivered from the reservoir 3 by the liquid delivery element 6 to generate the aerosol, and this is then inhaled by a user through the opening in the mouthpiece 35. The aerosol is carried from the aerosol source to the mouthpiece 35 along one or more air flow channels (not shown in Figure 1) that connect the air inlet(s) 26 to the aerosol source to the aerosol outlet when a user inhales on the mouthpiece 35. Since in this example the air inlets 26 to the system are located in the device component 20, the cartridge component 30 has its own air inlet(s) in air flow communication with the device component 20 so that air drawn in through the device component air inlet(s) 26 can reach the interior of the cartridge component 30, and the atomiser 7. In other designs, air inlets may be located in the outer wall of the cartridge component 30 so that air enters directly into the cartridge component 30 instead of arriving there via the device component 20.

[0051] The device component (control unit) 20 and the cartridge component (cartomiser, consumable) 30 are, in this example, separate connectable parts detachable from and reattachable to one another by movement in a direction parallel to the longitudinal axis, as indicated by the double-headed arrows in Figure 1. Each component 20, 30 has a connecting portion 21 , 31 at an end facing towards the corresponding end of the other component, and the components 20, 30 are joined together when the aerosol provision system 10 is ready for use or in use by cooperating engagement elements at the connecting portions 21 , 31 (for example, a screw or bayonet fitting, or a push-fit, snap-fit or magnetic connection) which provide mechanical and in the present case electrical connectivity between the device component 20 and the cartridge component 30. Electrical connectivity is required if the heater

[0052] 4 operates by ohmic heating, or where a vibrating mesh vapour generator or other electrically powered vaporiser is used, so that current can be passed through the heater 4 or otherwise supplied to the vaporiser, and / or to any other electrically powered parts in the cartridge component 30, when these parts in the cartridge component 30 are connected to the battery

[0053] 5 in the device component 20. In systems that use inductive heating, electrical connectivity for vapour generation can be omitted if no vapour generating parts requiring electrical power are located in the cartridge component 30, although electrical power may still need to be supplied to other electrical parts in the cartridge component. For inductive heating, an inductive work coil can be housed in the device component 20 and supplied with power from the battery 5, and the cartridge component 30 and the device component 20 shaped so that when they are connected, there is an appropriate exposure of the heater 4 to flux generated by the coil for the purpose of generating current flow in the material of the heater 4. For all non-inductively powered parts, the connecting portions 21 , 31 include electrical contacts to complete electrical circuits between the powered parts and the battery 5 when the cartridge component 30 and the device component 20 are connected together. Also, apertures for air flow from the device component 20 to the cartridge component 30 are included at the connecting portions 21 , 31 of the two components 20, 30 in designs having one or more air inlets 26 in the outer wall(s) of the device component 20. The connecting portions 21 , 31 therefore provide an interface between the cartridge component 30 and the device component 20. The Figure 1 design is merely an example arrangement, and the various parts and features may be differently distributed between the device component 20 and the cartridge component 30, and other undepicted elements may be included. The two components 20, 30 may connect together end-to-end in a longitudinal configuration as in Figure 1 , or in a different configuration such as a parallel, side-by-side arrangement. The system may or may not be generally cylindrical and / or have a generally longitudinal shape. Either or both components 20, 30 may be intended to be disposed of and replaced when exhausted (the reservoir 3 is empty or the battery 5 is flat, for example), or be intended for multiple uses enabled by actions such as refilling the reservoir 3, replacing the reservoir independently of the cartridge component 30, and recharging the battery 5. In other examples, the aerosol provision system 10 may be unitary, in that the parts of the device component 20 and the cartridge component 30 are comprised in a single housing and cannot be separated. Embodiments and examples of the present disclosure are applicable to any of these configurations and other configurations of which the skilled person will be aware.

[0054] During operation of an aerosol provision system, an amount of aerosol is generated during a puff on the system, the aerosol being delivered to the user via the mouthpiece for inhalation. The aerosol is generated by vaporisation of liquid taken from the reservoir, so the amount of aerosol in a puff corresponds to an amount of liquid vaporised to produce the puff, and as puffs continue, the liquid is consumed and the amount of liquid remaining in the reservoir reduces. In particular, a mass of the aerosol in a puff is related to the mass of the liquid used to generate the aerosol of that puff. It is proposed herein to use the relationship between aerosol amount generation and liquid consumption to estimate a remaining amount of liquid in the reservoir. By determining the mass of aerosol in one or more puffs, the remaining amount of liquid in the reservoir may be estimated by subtraction of the mass of aerosol that has been generated from a mass of liquid in the reservoir at a previous time, such as the total liquid mass in the reservoir when full if the total accumulated aerosol mass is tracked, or the liquid mass in the reservoir before a particular puff if the aerosol mass of that puff is determined. Mass is a convenient metric to use for this procedure, but other metrics might also be used, such as volume, or a relationship between one metric for aerosol amount and another metric for liquid amount.

[0055] Since the generated aerosol is delivered internally to the user via inhalation, it is not feasible to directly measure the amount of aerosol in an actual real life puff when the user uses the aerosol provision system. However, the amount of aerosol which is generated during a puff depends on characteristics of the aerosol provision system which are known or can be determined, and operating parameters of the aerosol provision system which can be measured. For example, more aerosol is generated in a longer puff than in a shorter puff, so aerosol amount depends on puff duration. A higher amount of power delivered to the vaporiser during the puff can also increase the amount of aerosol, for example by heating a heating element of the vaporiser to a higher temperature, so aerosol amount depends on vaporiser operating power level. Factors such as these can be readily measured during operation of an aerosol provision system, and the controller may be configured to use measured or otherwise ascertained values for these factors to determine an amount of aerosol in a puff using a predetermined relationship between these factors and aerosol amount. From this, a corresponding decrease in the amount of liquid in the reservoir can be determined, allowing a remaining amount of liquid to be estimated. This can then be reported or indicated to the user. The user can then be aware of their liquid consumption, and prepare for replacement or refilling of the reservoir as it approaches an empty state.

[0056] It is contemplated that any technique for determining aerosol amount in a manner that allows the amount of generated aerosol to be subtracted from the amount of liquid in the reservoir in a meaningful way may be used. As noted above, mass is a useful metric for this purpose. If mass is used, an approach proposed herein for determination of the mass of aerosol generated in a puff is to use a metric designated as aerosol collected mass (ACM).

[0057] The ACM may characteristically refer to a mass of aerosol collected, in laboratory or test conditions, externally from the aerosol provision system during one or more puffs of the device. The ACM may be determined for a given aerosol provision system under certain operating conditions by collecting aerosol in a laboratory aerosol analyser I puff analyser during one or more puffs carried out under controlled conditions of airflow (for example, of airflow duration and airflow rate profile) by the aerosol analyser. The aerosol for a known number of one or more puffs is collected, for example on a fibrous pad, or otherwise condensed out of the aerosol I vapour phase for analysis, and then weighed to determine its mass. The mass of aerosol generated in a puff by a known aerosol generating system operating with known values of operational parameters of the aerosol generating system is thereby determined.

[0058] Using this approach, the aerosol mass for a puff under various operating conditions can be ascertained from one particular example of the aerosol generating system. However, users in the future will be using other aerosol generating systems, which may not function identically to the tested aerosol generating system even if all the systems are of the same design. It is known that there can be considerable system-to-system variation that affects aerosol generation, arising from factors including manufacturing variation and user puff techniques, so that no two systems, even when of intended exactly identical design, will perform exactly identically and generate exactly the same amount of aerosol in a puff under identical operating conditions. In order to obtain meaningful ACM data which can employed for the purpose proposed herein of estimating liquid amount in a reservoir, it is proposed to collect ACM data from populations of aerosol provision systems of the same design or type, and use this data to empirically derive a relationship between aerosol mass per puff and values of operating parameters of the aerosol provision systems that can be applied, to determine aerosol mass per puff, in aerosol provision systems of the same or similar type which are later supplied to users. The use of data from a population allows an averaging effect across system- to-system variations, and it has been found that the resulting relationship provides a result which is accurate enough to enable reservoir liquid amount estimation at an accuracy level which is useful to users.

[0059] Another source of potential error may be noted, in that the collected mass of aerosol may differ from the mass of liquid which was vaporised, since some aerosol may condense in or on parts of the aerosol delivery system or the aerosol analyser or otherwise be diverted and not collected for weighing. Nevertheless, it has been found that this does not affect the measured data significantly enough to undermine the usability of the ascertained relationship for the purpose of estimated reservoir liquid amount, and may be ignored.

[0060] As with averaging techniques in general, the accuracy of the determined relationship between aerosol mass generated and values of the aerosol provision system operating parameters which is ascertained from ACM data obtained empirically as described above can be improved by increasing the size of the population of aerosol provision systems of the same type from which the data is collected. Hence, it is suggested that as large a population as possible is used, within limits set by factors such as time, cost, and the number of vaporisers and / or systems which are available for the purpose. For example, a population comprising about 20 or about 50 or about 100 individual vaporisers or aerosol provision systems (where individual vaporisers may for example be included within individual cartridges which are used in turn with the same device or a smaller number of devices to make complete aerosol provision systems) of the same type may be used to obtain a body of ACM data. Larger or smaller populations are not excluded, however.

[0061] It is recognised that many factors affect the amount of aerosol which is comprised within a single puff made on an aerosol provision system of a particular type and design. These include tolerances in part manufacturing and assembly, ambient pressure, humidity, ambient temperature, the temperature of the liquid, properties of the liquid, the strength of the puff (air flow rate through the system and past the vaporiser), puff duration, recent puff history, power level applied to the vaporiser, actual operating power of the vaporiser including electrical tolerances, and efficiency of the vaporiser. If account were to be taken of all the variables when attempting to determine the amount or mass of aerosol in any given puff, the determination would become very laborious. Moreover, some of the factors are not straightforward to measure or account for. Other factors have been determined by experiment to not have a significant effect, so may be ignored without detriment to the estimation. These include the temperature of the liquid and the time between puffs.

[0062] Accordingly, it is proposed herein to concentrate on a small number of readily measurable and verifiable parameters. It has been found that sufficient accuracy to enable meaningful reservoir liquid amount reporting to a user can be obtained by considering the level of electrical power applied to the vaporiser (which will typically be a heater, but as noted above, may not be), and the duration of the puff. These two parameters are typically straightforward to ascertain within an aerosol provision system. In some very simple systems, the power supply (battery) delivers only a fixed power level to the vaporiser, so that a single power level value can be provided to the controller of the aerosol provision system for use in liquid amount estimation. More sophisticated aerosol provision systems allow the user to set the power level, perhaps by selection of one power level from a quantity of available power levels, or by adjustment within an available continuous power level range. The selected power regime may correspond to a constant power level over a puff or to a profile of varying power level over a puff. The controller is configured to control the battery to supply the selected power level to the vaporiser, so that the controller has access to the value of the power level which is used for any given puff.

[0063] Regarding puff duration, some aerosol provision systems are “puff activated” and include a so-called puff detector or puff sensor, which is a sensor configured to detect when a user inhales on the system. Such sensors detect changes in air flow or air pressure, and are typically used to activate the aerosol provision system for operation. When an inhalation is detected, the sensor sends a signal to the controller, which responds by controlling the supply of power to the vaporiser so that vapour is generated, and stops the supply of power at the end of the puff, when the sensor detects that inhalation has ceased. In such an arrangement, the controller may be provided with a clock configured to time the length of the puff, so that the controller can thereby obtain a value of the duration of the puff. Other aerosol provision systems are activated by a user operated control element on the aerosol provision system, such as a switch or a button, by which the user indicates that aerosol generation is required, in response to which the controller controls the power to be supplied to the vaporiser. For example, the user may press a button at the same time as inhaling on the aerosol provision system, so that the vaporiser is powered for the duration of the button press. In such a system, a puff sensor may be provided for the sole purpose of allowing puff duration to be measured, as described above, rather than for activating aerosol generation. Alternatively, the operation of the user control element may be used as a proxy for puff duration, if it is assumed that the user will operate the user control element to obtain aerosol for approximately the duration of their puff. Hence, a clock may be provided which is configured to time the period between the start and stop of the user control operation, for example, the duration for which a button is pressed, or the time elapsed between a switch being turned on and then off. This time period can then be taken by the controller as a value for the duration of the puff.

[0064] Therefore, in order to obtain empirical data from which an appropriate equation relating aerosol mass to power level and puff duration can be derived, measurements of ACM can be made for a range of different known power level values and known puff duration values, using a population of aerosol provision systems of the same design and / or having a same design of vaporiser. The equation can then be obtained by fitting a function or functions to the empirical data.

[0065] Figure 2 shows a graph of empirical data obtained in this way from a population of aerosol provision systems of the same type, in that a population of pods or cartridges of the same design, each having an electrically powered vaporiser in the form of an electrical heating element and a reservoir of aerosolisable liquid, were used together with one or more different devices to form the population of aerosol provision systems. The graph indicates puff duration in seconds on the x-axis, and ACM per puff in milligrams on the y-axis. Each data point represents an amount of aerosol, as the ACM, per puff averaged over 25 puffs, measured in laboratory conditions. A selection of different power level values were used for each puff duration value, as indicated. It can be seen that for each power level value and puff duration value combination, the data points cluster together but do show some variation, arising from the pod-to-pod or system-to-system variation discussed further below. It is this variation that the proposed approach aims to address, by suggesting an implementation that turns variable experimental data obtained from a specific population of aerosol provision systems into a workable algorithm applicable to a wider group of the same type of aerosol provision system when used in real world conditions.

[0066] Figure 3 shows the graph of Figure 2, with best fit linear functions also shown, for each power level value. Hence a group of best fit lines is obtained, each relating ACM to puff duration value, for each power level value. The functions describing these lines can be then be combined in order to obtain an equation that relates both power level value and puff duration value to ACM. If the ACM is taken as corresponding to the actual mass of aerosol in a puff, M in milligrams, and purely as an example, the equation may have the following form: M = A - Bt - CP + DtP where A, B, C and D are constants, t is the puff duration value in seconds and P is the power level value in watts. As an illustration, for one particular aerosol provision system type, values for the constants were determined to be A = 0.760722, B = 1.150802, C = 0.432436 and D = 0.622964. The skilled person will understand that different values for the constants, and indeed a different form for the equation, may be determined from other empirical data and other mathematical techniques.

[0067] Two sources of error can be identified when using an equation of this type, obtained by linear fitting to empirical data. There is a systematic error arising from the mathematical approach taken to derive a single equation from a spread of data points. The value of the aerosol mass predicted using the equation may fall relatively far from the mean of the empirical data, so that a calculated aerosol mass may not accurately reflect the actual aerosol mass in a real puff. This may be found to be worse in some operating regions, for example in the box 40 in Figure 3 for the illustrated empirical data, and at shorter puff durations, as shown in the magnified inset 42. These issues may to some extent be addressed by collecting empirical data from a larger population of aerosol provision systems, to improve the accuracy of the function fitting. There is also the random pod-to-pod or system-to-system error mentioned above, arising from manufacturing and operational differences and variations between vaporisers, reservoirs and overall aerosol provision systems. Even if the best-fit line is very accurate so that the equation can perfectly predict the mean value for the aerosol mass at a puff-duration and power level combination, there will be variation around the mean which is unpredictable so that in a real life situation the calculated aerosol mass will likely differ from the actual aerosol mass in an actual puff. Nevertheless, it has been found that the proposed approach is still sufficiently accurate to enable useful estimation of remaining liquid amount that can be reported to the user is a meaningful way.

[0068] While linear fitting to empirical data is straightforward to achieve, and may provide a relatively simple equation that can be efficiently computed to calculate aerosol mass during use of an aerosol provision system, more complex fitting may be applied to the empirical data in some other examples, by fitting a nonlinear function to the data. This can improve accuracy of the determined aerosol mass. Any nonlinear mathematical function may be chosen to best fit a curve to the empirical data; the skilled person will understand how to achieve this with reference to the nature of the data obtained from the laboratory measurements. Examples of suitable functions include, but are not limited to, a quadratic or cubic polynomial function, or a polynomial function of higher order, a spline function, or a piece-wise linear function.

[0069] Figure 4 again shows the graph of Figure 2, and differs from Figure 3 in that best fit nonlinear functions are shown fitted to the data for each power level value. As before, the functions describing the best fit lines can be then be combined in order to obtain a single equation that relates both power level value and puff duration value to ACM. Again, this equation can be used to calculate aerosol mass in a puff from the power level value and duration of the puff. A comparison of Figure 4 with Figure 3 shows that the systematic error is reduced compared to the linear fitting, and is much closer to zero since the predicted value, indicated by the line, is much closer to the mean of the measured data. The unpredictable pod-to-pod variation remains, but on average the overall error should be lower than when linear fitting is used. Improvement is particular significant at lower puff durations, as indicated by the magnified inset 44. To improve this further, more empirical data could be collected for shorter puff durations, for example, for other puff duration values near to one second, such as at and / or between 0.5 seconds and 1 .5 seconds.

[0070] Hence, an equation that relates aerosol mass of a puff to the power level value at the vaporiser used to generate the aerosol in the puff, and the value of the duration of the puff, can be obtained from empirical data measured in laboratory conditions. This equation can be provided to the controller of an aerosol provision system, and stored in memory of the controller (or memory accessible by the controller). The controller is configured to obtain a value of the power level and a value of the puff duration during puffs taken on the aerosol provision system, as described above. When the user takes a puff on the aerosol provision system, the controller obtains the power level value and the puff duration value, and uses these values, with the equation, to determine a mass of the aerosol contained in the puff that has been taken. The controller is further configured to use the determined mass of aerosol to estimate an amount of liquid in the reservoir of the aerosol provision system.

[0071] Broadly, the estimation is achieved using the determined mass of aerosol in the puff and a known amount of liquid in the reservoir prior to the puff. This may be implemented in a variety of ways, in which the controller obtains or is provided with a value for the total capacity of the reservoir, being the initial amount or volume of liquid contained in the reservoir when it is full (or otherwise filled or provided with liquid in advance of first use), before any puffs have been taken. In some configurations, the pod or reservoir may not be replaceable, and the controller is provided during manufacture with a value for the total capacity of the reservoir. This may or may not be a mass; it could alternatively be a volume, which the controller is configured to convert to a mass, for example. In configurations in which the pod or reservoir can be replaced, it may be that only reservoirs of a single capacity or single initial liquid fill amount or level are provided by the manufacturer, so that the value of this capacity is provided to the controller during manufacture, and the controller is configured to recognise when a new pod or reservoir is fitted, so that the amount of liquid in the reservoir at that time can be assumed to be equal to the pre-provided value for the total or initial capacity. In more complex arrangements, the controller may be configured to obtain an expected amount of liquid in the reservoir when the reservoir or pod is newly fitted to the aerosol provision system, or newly filled, that is, a value for the total liquid capacity of reservoir when it is full. It is known to provide reservoirs and / or pods / cartridges with identifying elements which can be read by a controller when the reservoir or pod is coupled to the device of the aerosol provision system in order to obtain identification information about the reservoir / pod. In the current context, this information may include or otherwise indicate a value of the reservoir’s total liquid capacity. The identification information may include items of data or information about the pod or reservoir, or may give a simple identification of the pod / reservoir from which the controller is able to ascertain the data or information, for example from a store of such data or information for different pods / reservoirs held in the controller or accessible by the controller from elsewhere. Examples of identifying elements include resistors, capacitors, chips or other electrical or electronic components in circuitry in the pod that can be electrically detected or interrogated by the controller, bar codes, QR codes or other indicia that can be optically read or otherwise sensed by a sensor or detector operated by the controller, and shaped features that engage with complementary features in or on the device, where the controller can sense the engagement. Other examples are not excluded. Where a refillable reservoir is provided, a refilling action may be detected, and reported to the controller, which can assume that after refilling the reservoir contains a liquid amount matching its total liquid capacity. Once the controller has obtained the total liquid capacity for the filled reservoir, the amount of liquid consumed from the reservoir by conversion to aerosol in a puff can be determined per puff using the equation, and deducted from the known total liquid capacity in the reservoir to estimate the amount of liquid remaining in the reservoir. The controller may store the new, reduced amount of liquid, and deduct the aerosol amount in the next puff from that amount, and so on. In other words, the controller keeps track of the amount of aerosol in the reservoir as it depletes after each puff, and subtracts the aerosol amount of the each puff from the reservoir aerosol amount immediately prior to the puff. Alternatively, the controller may accumulate the total amount of aerosol generated by adding the aerosol amount in each puff to the amount in the previous puffs, and subtract the total aerosol amount from the original reservoir total liquid capacity when an estimate of the remaining liquid amount in the reservoir is required.

[0072] The estimate of the liquid amount in the reservoir may be stored by the controller and used internally by processes of the aerosol provision system, and / or it may be indicated or reported to the user. An example of a process may be automatic ordering of a replacement pod when the reservoir approaches depletion, if the aerosol provision system is configured for communication with a remote server or with a personal electronic device of the user such as a mobile phone. Indicating to the user may be done regularly or periodically, or on demand when the user operates a user control of the aerosol provision system to request an indication, or only when the reservoir is approaching an empty state (the remaining liquid amount falls below a predetermined threshold, for example) in order to warn the user that the supply of liquid is about to run out.

[0073] The controller may be configured to store the equation, and directly use the equation to determine the mass of aerosol in a puff by utilising the obtained values of power level and puff duration in the equation. This approach requires computation by the processor for each puff, but has a low storage requirement since only the equation needs storing. It can also give a relatively accurate determination of the aerosol amount for each puff, since the equation returns a value for the aerosol amount for any value of puff duration and power level; the equation performs an extrapolation between the selected discrete values of puff duration and power level for which the empirical data was collected, which may not correspond to the puff duration value and / or of the power level value for an actual puff.

[0074] In other examples, the controller may store a look-up table that stores, for multiple combinations of puff duration value and power level value, a corresponding value for the mass of aerosol in a puff with that combination of puff duration and power level. The controller is configured, when a puff takes places, to retrieve, from the look-up table, an aerosol mass value corresponding to the values of power level and puff duration that the controller has obtained for that puff. The look-up table therefore maps values of power level and values of puff duration to values of aerosol mass. The provision of a look-up table reduces computation by the controller, since there is no need to calculate a value for the equation for each puff, but has an increased storage requirement since a look-up table will be larger than the equation. Also, accuracy may be reduced, since the look-up table can comprise only a limited selection of possible values for the puff duration and the power level. In actuality, the puff duration, and possibly also the power level (depending on power selection implementation in the aerosol provision system) may take any value which may not correspond directly to a value in the lookup table. The controller therefore may therefore allocate an obtained value to the nearest value recorded in the look-up table, or it may always round up or round down the obtained value to the next recorded value. Alternatively, the look-up table may be configured to contain ranges of values of puff duration and / or power level, where the ranges map onto single values for aerosol mass. The look-up table may be populated using the equation to determine values for aerosol mass per puff for a selection of different power levels and puff durations, which may or may not correspond to the values for power level and puff duration used to collect the original empirical data.

[0075] Figure 5 shows a highly simplified schematic representation of an example of an aerosol provision system configured to implement remaining liquid amount estimation as described herein. The aerosol provision system 10 is similar to the example shown in Figure 1 , and comprises a device component 20 and a cartridge or pod component 30. The system 10 may be unitary, or the pod component 30 may be replaceable. As before, the pod component 30 comprises a reservoir 3 for storing aerosolisable liquid, and having a total liquid capacity when full of liquid. The pod component 30 may be supplied with (or filled to) an initial amount or volume of liquid equal to or less than the total capacity of the reservoir 3. The pod component 30 also comprises a vaporiser 4 for vaporising liquid from the reservoir in order to generate aerosol for delivery to the user during a puff. Also as before, the device component comprises a battery 5 for supplying electrical power to the vaporiser 4, and a controller 28 for controlling the supply of power from the battery 5 to the vaporiser 4. The controller 28 comprises a processor 22 for performing operations and actions such as controlling the supply of power, and estimating remaining liquid amount in the reservoir 3 as described herein. The controller 28 has a memory 23, in which is stored an equation for determining the aerosol amount in a puff, or a look-up table derived from the equation, as described above. The controller 28 also has a clock 24 for timing puff duration, either via a puff detector 32 or via detection of user operation of a button or other user operable control 27 to activate the vaporiser, again as described above. The pod component 30 may include an identifying element from which the controller may obtain a value for the reservoir’s initial volume of liquid, before puffing commences, again as described above. Finally, the aerosol provision system 10 may be provided with an indicator 29 such as a visual display on or in an outer housing or wall of the aerosol provision system 10, and operable by the controller 28 to display an indication of an estimated remaining liquid amount in the reservoir 3 (such as a numerical or graphical indication, which may be an indication of the proportion of the remaining liquid amount compared to the initial amount, or an absolute indication). Note that some parts of the aerosol provision system may be located differently from the Figure 5 example, for example within the other of the pod component and the device component.

[0076] The above examples have utilised vaporiser power level and puff duration as variable operating parameters that are taken into account to determine the amount of aerosol in a puff. As already mentioned, a variety of factors can affect the amount of aerosol in a puff, some of which can be considered as more or less difficult to account for or considered as more or less significant in their effect. It has been found that a factor which merits attention is the type or composition of the liquid in the reservoir, from which the aerosol is generated. It has been determined that liquid type can have a relatively significant effect on the amount of aerosol generated in a puff. The term “liquid type” is intended to acknowledge that liquid aerosol forming substrate that is vaporised to generate aerosol for delivery by an aerosol provision system is available in many different compositions, which may show differences in vaporisation behaviour under otherwise same or similar conditions. Liquids of different nicotine strength and different flavour are readily available, for example, and may be composed of different ingredients and differing proportions of ingredients, which may affect the rate and temperature at which the liquid vaporises. Hence, puffs at equal power and of equal duration carried out on the same aerosol provision system using different liquids may tend to contain different masses of aerosol. Accordingly, the use of a single equation to determine aerosol mass per puff without regard to the liquid type may produce varying accuracy of estimation of the remaining liquid amount.

[0077] It may be that a particular aerosol provision system is configured to only be used with a single liquid type. For example, the aerosol provision system may be of a design in which the pod or the reservoir cannot be replaced, or the reservoir cannot be refilled, and the system is made available prefilled with only a single type of liquid. In such a case, there is no need to take account of the type of liquid in estimating the remaining liquid amount in the reservoir. All that is required is that the empirical data from which the equation used by the controller for determining aerosol amount in a puff is collected using the same type of liquid as is contained in the reservoir, or alternatively a type of liquid with the same or similar vaporisation characteristics as the liquid type contained in the reservoir so that the equation is applicable and give sufficiently accurate results. In the current context, therefore, liquid of a particular type is considered to have vaporisation characteristics or behaviour different from liquid of another type. Two liquids of different type have different vaporisation behaviours,

[0078] In other cases, aerosol provision systems of an otherwise same or similar design and configuration are often supplied to the user prefilled with a choice of different liquid types. Other aerosol provision systems are configured to allow the user to consume different liquid types, by replacement of the pod or the reservoir with a pod or reservoir that may contain a different liquid type, or by refilling of the reservoir with a different liquid type. Hence, there are many circumstances in which a user may be consuming liquid which is of a different type to that for which empirical data for obtaining the equation was collected. In the current context, liquid of a particular type is considered to have a composition different from liquid of another type.

[0079] An approach to handling different liquid types can be to obtain empirical data for a range of different liquid types so that equations for determining aerosol mass per puff can be derived for different liquid types or that otherwise take account of liquid type. However, this approach can require a substantial amount of laboratory work and resources in order to collect the empirical data. Data storage requirements for the controller are increased if multiple equations or look-up tables for different liquids are stored, and there is a requirement for the controller to be able to ascertain the liquid type so as to apply the appropriate equation when determining the aerosol mass in a puff.

[0080] Since the origin of the complexity in estimating liquid amounts for different liquid types lies in the potentially different vaporisation behaviour exhibited by different types of liquid, an alternative approach is proposed herein. It is proposed that the equation for determining aerosol mass in a puff is obtained for liquid of a specified type vaporised in a specified aerosol provision system (in that the configuration of the aerosol provision system is known and specified, for example with a specified type of vaporiser), and used by the controller of an aerosol provision system in use by a user to estimate liquid amount in the reservoir, as described above, and that a feature of the aerosol provision system itself is modified compared to the specified aerosol provision system in order to compensate for the difference or differences in vaporisation behaviour of the liquid type in the aerosol provision system compared to the specified liquid type for which the equation is obtained. The aim is to adjust the vaporisation performance of the aerosol provision system in such a way that, for a given power level and puff duration the same or approximately the same aerosol mass is produced from the liquid in the aerosol provision system (which we may refer to as a first liquid) as for the specified liquid in the specified aerosol provision system, and / or the rate of liquid consumption by vaporisation is the same or approximately the same, and / or a same or similar number of puffs is required to empty the reservoir. In this way, the equation or look-up tables obtained for the specified liquid type can be directly used by the controller to estimate liquid amounts for a different liquid type without any adjustment of the equation or selection between equations, and with no requirement for the controller to ascertain the liquid type in the reservoir in order to correctly apply the equation.

[0081] It is contemplated that a variety of features or characteristics of the aerosol provision system may be modified in order to compensate for a different vaporisation behaviour of the liquid of the first type in the reservoir as compared to the specified liquid type.

[0082] A first example of a feature of the aerosol provision system that may be modified is an initial amount or volume of the first liquid in the reservoir. This is described in more detail below.

[0083] A second example of a feature of the aerosol provision system that may be modified is a composition of the first liquid. As noted above, different compositions or recipes of liquid can produce variations in vaporisation behaviour. In order to adjust for this, the composition of the first liquid can be tailored such that, although the composition is different from the composition of the specified liquid, its vaporisation behaviour is made the same, substantially the same, or similar to that of the specified liquid. For example, a flavour component in the first liquid which is different from a flavour component in the specified liquid may give a different vaporisation behaviour if the liquid compositions are otherwise the same. To compensate, one or more other components or amounts I proportions of other components in the first liquid can be altered in order to adjust the vaporisation behaviour back to or towards the vaporisation behaviour of the specified liquid. This second example is also described in more detail below. A third example of a feature of the aerosol provision system that may be modified is a configuration of the vaporiser. If the first liquid type and the specified liquid type exhibit different vaporisation behaviours, an aim in achieving liquid amount estimation accuracy is to have the two liquid types produce a same aerosol mass in a puff for the same puff duration and same power level applied to the vaporiser. If the first liquid type vaporises more rapidly or at a lower temperature, the vaporiser can be modified so that it reaches a lower temperature or outputs less heat energy than the vaporiser in the specified aerosol provision system for the same applied power level. If the first liquid type vaporises more slowly or at a higher temperature, the vaporiser can be modified so that it reaches a higher temperature or outputs more heat energy than the vaporiser in the specified aerosol provision system for the same applied power level. The electrical resistance of the vaporiser can be selected to achieve this, for example, by altering the materials or the structure of the vaporiser. This third example is also described in more detail below.

[0084] A fourth example of a feature of the aerosol provision system that may be modified is a configuration of an air flow path in the aerosol provision system. The aerosol mass in a puff depends in part on the rate at which vapour produced by the vaporiser is picked up by air flowing past the vaporiser and entrained as aerosol delivered to the user for inhalation. A larger volume of air or a faster air flow speed may collect more vapour for a given puff duration than a smaller volume of air or a slower air flow speed. Hence, if the first liquid type vaporises rapidly so that a large amount of vapour can be converted to aerosol during a puff if there is sufficient air flow to carry the vapour away from the vaporiser as rapidly as it is generated, decreasing the amount of air flow past the vaporiser during a puff will reduce the mass of aerosol in a puff. If the first liquid type vaporises more slowly so that vapour is generated at a slower rate, increasing the amount of air flowing past the vaporiser during a puff will collect the vapour and carry it away from the vaporiser more efficiently and allow more vapour and more aerosol to be produced so that the mass of aerosol in a puff is increased. Accordingly, the mass of aerosol for a given power level and puff duration produced from the first liquid can be adjusted up or down to match or approximately match the mass of aerosol for the same power level and puff duration produced from the specified liquid in the specified aerosol provision system. The amount or speed of air flow can be altered by modifying the configuration or structure of the air flow path in the aerosol provision system in which the vaporiser is located. This fourth example is also described in more detail below.

[0085] Other modifications to the aerosol provision system that can compensate for a difference in vaporisation behaviour between the first liquid and the specified liquid may be apparent to the skilled person and are not excluded. The first example given above, in which compensation of the vaporisation behaviour is achieved by adjustment of the initial liquid volume of the first liquid type in the reservoir, will now be described in more detail.

[0086] A difference in vaporisation behaviour between two types of liquid may have the effect that, for the same power level and puff duration, and otherwise for the same or similar configuration of the aerosol provision system, a different mass of aerosol is generated per puff. Hence, a different number of puffs will be required to consume the same volume of one liquid than the other liquid. A reservoir full of a liquid type that produces more aerosol mass per puff will therefore be emptied in fewer puffs than the same reservoir full of a liquid type that produces less aerosol mass per puff. Hence, if the equation used by the controller to estimate the amount of liquid remaining in the reservoir after a puff has been obtained from empirical data relating to a different liquid type, the estimate will not be accurate.

[0087] This can also be thought of as the rate of consumption of liquid being different for otherwise matching operating conditions. Different types of liquid will be consumed at different rates, owing to different aerosol masses being produced per puff. It is proposed that this can be addressed by arranging that the initial amount or volume of the liquid type which is provided in the reservoir of a newly supplied aerosol provision system is adjusted compared to a specified initial amount or volume of the specified liquid type provided in a reservoir of the specified aerosol provision system used to obtain the empirical data for deriving the equation provided to the controller of the aerosol provision system. If the liquid is of a type that is converted to vapour more rapidly, the initial volume is made larger than the specified initial volume. If the liquid is of a type that is converted to vapour less rapidly, the initial volume is made smaller than the specified initial volume. In this way, the total amount of vaporisation in terms of puff and power required to consume all the liquid in the reservoir can be matched to the empirical data, and the equation will give an accurate estimation of the remaining liquid amount despite differences in vaporisation behaviour of the two types of liquid.

[0088] This approach accepts the difference in vaporisation behaviours between different liquid types and allows the aerosol mass per puff to remain different for the first liquid type compared to the specified liquid type under the same conditions. The adjustment to compensate for the difference lies in changing the total amount of liquid provided for those puffs, so that over the lifetime of the initially filled reservoir, the puffing activity required to empty the reservoir is made the same for both liquid types. The rate of consumption from full to empty, where “full” indicates the initial volume of liquid supplied in the reservoir (which may or may not be the reservoir’s maximum capacity, as discussed further below), is made the same, and the equation obtained for the specified liquid type becomes applicable to the actual or first liquid type. A way to implement this adjustment in the initial fill volume of the reservoir is to compare the aerosol mass per puff for a known puff duration and known power level for the first liquid (determined using ACM measurements, for example) with the aerosol mass per puff of the same duration at the same power level for the specified liquid (known from the empirical ACM measurements collected to derive the equation, or calculated retrospectively using the equation). The ratio or proportion of the aerosol masses can be used as a proportion for the initial fill volume of the first liquid type compared to the initial volume of the specified liquid type used when collecting the empirical data from the specified aerosol provision system.

[0089] Let us designate the aerosol mass in a puff of given duration and given power level for the first liquid type as AF, and the aerosol mass in a puff of the given duration and the given power level for the specified liquid type as As. The ratio or proportion of these can be designated as N, where N = AF / As. If the specified initial volume of the specified liquid type is Vs, the initial volume of the first liquid type which should be filled into the reservoir of the aerosol provision system is therefore V = N * Vs. If the first liquid type has a vaporisation behaviour that gives a lower production of aerosol and hence a reduced aerosol mass per puff, N is less than 1 , and V is less than Vs. If the first liquid type has a vaporisation behaviour that gives a higher production of aerosol and hence an increased aerosol mass per puff, N is greater than 1 , and V is greater than Vs.

[0090] This modification in initial liquid volume can be implemented using reservoirs of a same capacity across a range of aerosol provision systems which are supplied to users with different types of liquid (for example a selection of flavours and / or nicotine levels), or by using reservoirs of different capacity across the range of aerosol provision systems. In this context, the capacity of a reservoir is considered to be its total interior storage volume available for holding liquid, and thereby corresponding to the maximum volume of liquid that can be accommodated in the reservoir. A full reservoir will hold an initial volume of liquid which is equal to the capacity of the reservoir. Clearly, a reservoir is capable of holding an initial volume which is less than the capacity, if the reservoir is not completely filled with liquid when the liquid is first placed in the reservoir during manufacture of the aerosol provision system. Having a constant reservoir capacity across a range of aerosol provision systems is simple in terms of system design and manufacture, since it allows all systems to use the same configuration of reservoir. However, the maximum initial volume of the first liquid type that can be provided is then limited to the capacity of the reservoir, so that liquids of a type that vaporise more rapidly than the specified liquid and therefore need to be provided in a large initial volume cannot be used while still maintaining accuracy of estimation of the remaining liquid amount. This can be addressed by choosing a liquid with a very high vaporisation rate and large aerosol mass per puff as the specified liquid type to obtain the empirical data, with the expectation that all other types of liquid that will be interest will likely have a lower vaporisation rate and a smaller aerosol mass per puff. This will ensure that N for any liquid of interest is not greater than one, and the modification in the initial volume of the liquid required to make the equation accurate is a reduction in the initial volume compared to the specified initial volume. If the specified initial volume is selected to match the reservoir capacity, the initial volume for the first liquid type will never be greater than the reservoir capacity, and the fixed reservoir configuration will then always be able to hold the required amount of any first liquid type. However, this approach may be considered undesirable in aerosol provision system designs in which the user is able to see into the interior of the reservoir (the reservoir having transparent walls), since a new aerosol provision system might appear to have been supplied with a deficient amount of liquid if the user is able to readily perceive that the reservoir is not full to capacity before first use of the aerosol provision system.

[0091] This can be addressed by configuring the aerosol provision system such that the user cannot see into the reservoir interior, or by utilising a range of reservoirs of different capacity. In the latter case, an appropriate reservoir can be selected with a capacity that matches or is close to the required initial volume for the liquid of the first type. The reservoir can then be filled to or close to capacity when providing the initial volume of the first liquid type, and the user will not infer any shortage of liquid on purchasing the aerosol provision system.

[0092] Figure 6 shows a schematic representation of a range of reservoirs holding initial liquid amounts or volumes according to the above example of reservoirs of equal capacity. The reservoirs 3 are shown in simplified form without any liquid outlet or associated vaporiser. On the left a reservoir 3 has a capacity C and is shown completely filled with liquid 8 of one type (which may be the specified liquid type) up to the full capacity C. This can be considered to be the specified initial volume Vs. In the centre a reservoir 3 with the same capacity C is filled with liquid 8a of a different type to a initial volume VF, where the liquid 8a has a lower vaporisation rate or aerosol mass per puff than the liquid 8 in the reservoir s on the left. Hence, N < 1 and VF < Vs. On the right a reservoir 3 also has the same capacity C, but contains an initial volume VF’ of liquid 8b of another different type, with a still lower vaporisation rate or aerosol mass per puff, so that N « 1 , and VF’ < VF < Vs. In this example, it is not possible to accommodate a liquid of a type for which N > 1 , since it is not possible to fit an initial volume VF > Vs into a reservoir since VF > C also.

[0093] Figure 7 shows a schematic representation of a range of reservoirs holding initial liquid amounts or volumes according to the above example for reservoirs of different capacity. Again, the reservoirs are shown in simplified form without any liquid outlet or associated vaporiser. The reservoirs 3, 3a, 3b as shown from left to right have decreasing capacities, and when filled with liquids 8, 8a, 8b to their maximum capacities contain initial volumes of liquid Vs, VF and VF’, where Vs > VF > VF’ as described above with regard to Figure 6. Also shown in a reservoir 3c which has a larger capacity than the reservoir 3, and is therefore able to hold, when full, the correct initial volume of a first liquid type 8d for which N > 1 and therefor VF” > VS.

[0094] In summary, by scaling the initial volume of liquid provided in a reservoir of an aerosol provision system in proportion with the ratio of the aerosol mass per puff for that type of liquid to the aerosol mass per an equivalent puff for the specified type of liquid, an equation for use in estimating a remaining liquid amount in the reservoir which was derived for the specified liquid type rather than the liquid in question can be accurately used. An initial volume that is N times (where N may be greater than 1 , less than 1 or 1) a specified initial volume of the specified liquid type used when collecting empirical aerosol mass data for deriving the equation can be provided in the reservoir when the aerosol provision system is fabricated, where N is the ratio of the aerosol masses per puff for the two liquid types. This can avoid the need to collect ACM measurements for a plurality of different liquid types, and the need to derive an equation relating aerosol mass per puff to puff duration and power level for a plurality of liquid types. The controllers of aerosol provision systems prefilled with different liquid types having different vaporisation behaviours can then all be provided with the same software and data (or configured with the same circuitry) configured for the estimation of the liquid amount remaining in the reservoir after one or more puffs, which will yield accurate estimation despite the different vaporisation behaviours. Scaling of the initial volume of liquid in the reservoir in proportion with the aerosol mass per puff versus that for a specified liquid compensates for vaporisation behaviour.

[0095] The provision of reservoirs pre-filled differing initial volumes of liquids according to liquid type can be implemented in aerosol provision systems that are provided the users in a unitary format and intended for disposal once the reservoir is empty, or in cartridges or pods that include a reservoir and a vaporiser and are configured for coupling to a device component to form the complete aerosol provision system, or as stand-alone reservoirs that are configured for installation in a cartridge or pod or an aerosol provision system.

[0096] Figure 8 shows a flow chart of steps in a first example method for estimating a liquid amount in an aerosol provision system, generally in line with features of the preceding disclosure. The method may be performed by a controller comprised within an aerosol provision system, such as within a device component of an aerosol provision system that can be coupled to a cartridge or pod component to form the complete aerosol provision system. In a first step S1 , a power level value is obtained, being a level of power which is applied a vaporiser of the aerosol provision system during a puff taken by a user of the aerosol provision system. The vaporiser operates under the supply of electrical power to generate aerosol for the puff by vaporising liquid from the reservoir. In this example, liquid in the reservoir is a first liquid type. The aerosol provision system includes a modification compared to a specified aerosol provision system that vaporises liquid of a specified type which is different from the first liquid type. The modification is implemented to compensate for a difference in vaporisation behaviour between the liquid of the first type and the liquid of the specified type. Some examples of possible modifications are described above. In a second step S2 (noting that steps S1 and S2 may be reversed in order or carried out simultaneously), a puff duration value is obtained, being a duration of the puff for which the power at the obtained power level value has been applied to the vaporiser. Once the power level value and the puff duration value have been obtained, the method proceeds to step S3, in which a mass of aerosol in the puff is determined from the power level value and the puff duration value. The mass of aerosol is determined using an equation relating power level and puff duration to mass of aerosol which is a function fitted to empirical data from measurements of mass of aerosol generated during puffs of known puff duration value at known power level value previously made on a population of aerosol provision systems of the specified configuration and vaporising the specified liquid type. Once the mass of aerosol in the puff has been determined, the method proceeds to step S4, in which an estimation is made of an amount of liquid in the reservoir, using the determined mass of aerosol and a known amount of liquid that was in the reservoir prior to the puff.

[0097] Figure 9 shows a flow chart of steps in a second example method for estimating a liquid amount in an aerosol provision system, generally in line with features of the preceding disclosure. The method may be performed by a controller comprised within an aerosol provision system, such as within a device component of an aerosol provision system that can be coupled to a cartridge or pod component to form the complete aerosol provision system. In a first step S1A, a power level value is obtained, being a level of power which is applied a vaporiser of the aerosol provision system during a puff taken by a user of the aerosol provision system. The vaporiser operates under the supply of electrical power to generate aerosol for the puff by vaporising liquid from the reservoir. In this example, liquid in the reservoir is a first liquid type. The aerosol provision system includes a modification compared to a specified aerosol provision system that vaporises liquid of a specified type which is different from the first liquid type. The modification is implemented to compensate for a difference in vaporisation behaviour between the liquid of the first type and the liquid of the specified type. In this example, the modification comprises a difference in an initial volume of the liquid of the first type in the reservoir of the aerosol provision system compared with a specified initial volume of the liquid of the specified type in the specified aerosol provision system. In a second step S2A (noting that steps S1A and S2A may be reversed in order or carried out simultaneously), a puff duration value is obtained, being a duration of the puff for which the power at the obtained power level value has been applied to the vaporiser. Once the power level value and the puff duration value have been obtained, the method proceeds to step S3A, in which a mass of aerosol in the puff is determined from the power level value and the puff duration value. The mass of aerosol is determined using an equation relating power level and puff duration to mass of aerosol which is a function fitted to empirical data from measurements of mass of aerosol generated during puffs of known puff duration value at known power level value previously made on a population of aerosol provision systems of the specified configuration and vaporising the specified initial volume of the specified liquid type. Once the mass of aerosol in the puff has been determined, the method proceeds to step S4A, in which an estimation is made of an amount of liquid in the reservoir, using the determined mass of aerosol and a known amount of liquid that was in the reservoir prior to the puff.

[0098] The second example noted above, in which compensation of the vaporisation behaviour is achieved by modification of a composition of the first liquid, will now be described in more detail.

[0099] More specifically, it is contemplated herein that the feature of the aerosol provision system that may be modified is a composition of the first liquid. As noted above, different compositions or recipes of liquid can produce variations in vaporisation behaviour. In order to adjust for this, the composition of the first liquid can be tailored such that, although the composition is different from the composition of the specified liquid, its vaporisation behaviour is made the same, substantially the same, or similar to that of the specified liquid. For example, a flavour component in the first liquid which is different from a flavour component in the specified liquid may give a different vaporisation behaviour if the liquid compositions are otherwise the same. This can arise when producing a range of liquids of different flavours, to provide choice to the consumer, which is done most simply by merely using a different flavouring component in an otherwise identical liquid recipe to make each flavour of liquid. This can result in a range of liquids which are ostensibly the same apart from flavour, but which demonstrate differences in vaporisation behaviour such that it is not possible to obtain accurate estimation of remaining liquid amounts by using a single equation in a controller of a model of aerosol provision system provided to vaporise these liquids.

[0100] To compensate, it is proposed that one or more components and / or amounts I proportions of components in a liquid of a first type be altered in order to adjust the vaporisation behaviour back to or towards the vaporisation behaviour of the specified liquid used when deriving the equation. A composition of the first liquid type is modified compared to the composition of the specified liquid type in order that the first liquid type has a same vaporisation behaviour as the specified liquid type. The composition of the first liquid type may be selected such that a mass of aerosol generated by the vaporiser of the aerosol provision system in a puff of a given puff duration and with a given level of power applied to the vaporiser using the first liquid type is the same as the mass of aerosol determined using the equation with a given puff duration value and the given power level value. Since the equation is derived from ACM measurements of the specified liquid type with the same configuration or specification of vaporiser, this composition selection of the first liquid type is in effect an alignment of the vaporisation behaviours of the first liquid type and the specified liquid type, for the same puff duration and vaporiser power level, the two liquid types produce the same mass of aerosol. Therefore, the equation is accurate for liquid amount estimation in consumption of the first liquid type, despite the equation having been obtained for the specified liquid type, of a different liquid composition.

[0101] The composition of a liquid for vaporisation in an aerosol provision system can be understood herein as the different components or ingredients that make up the liquid, and their relative proportions within the liquid. This can be thought of as a recipe for the liquid, which specifies which ingredients should be combined in what proportions in order to make the liquid. The proportion of each ingredient may be a percentage of that ingredient relative to the whole of a volume of liquid, for example. The main ingredients typically present in a liquid are flavouring (which may itself be a combination of different components to produce a desired flavour / taste effect for the liquid when vaporised), nicotine (which may be in a salt form), propylene glycol (PG) and vegetable glycerin (VG), and sometimes water. Nicotine is of course omitted in zero-nicotine liquids, but otherwise can be included in different proportions in different liquids, to offer a range of nicotine “strengths” of liquid to the consumer. The PG and VG act as diluents for the nicotine. Also, the PG carries the flavouring, and the amount of PG can govern the strength of flavour and also throat “hit” experienced by the user during a puff (included to emulate the effect of smoking a traditional cigarette). The VG is included to create a visible vapour / aerosol cloud, again emulating the experience of a traditional cigarette. Often, the PG and VG are included in equal proportions as this is considered to balance the flavour delivery and cloud effect in a way acceptable to many users. In other liquids the proportions may be varied, with a larger proportion of PG delivering a stronger flavour effect and a harsher throat hit with a reduced cloud , and a larger proportion of VG producing a larger or more distinct cloud effect with a weaker flavour and smoother throat feel. Other ingredients may also be included, typically in small amounts. Many flavours and nicotine levels are typically made available to the consumer, and the ratio of PG and VG is often offered at different levels to allow the user to select their preferred aerosol consumption experience. Hence, a large variety of liquid types may be produced.

[0102] PG and VG make up the bulk of a given volume of liquid, with flavouring and nicotine included in small proportions only. PG is an odourless thin liquid; it has low viscosity. VG is a thick liquid with a sweet flavour; it has a higher viscosity. Consequently, the proportion or ratio of PG and VG within a liquid tends to govern the overall viscosity of the liquid. In turn, the viscosity can have a significant effect on the vaporisation behaviour of the liquid. This may be inherent, and related to or similar to changes in surface tension and density that can also arise from changing the PG:VG ration. Also, the effect may arise from the behaviour of the liquid within the aerosol provision system, since a less viscous liquid may be delivered more quickly or efficiently to the vaporiser than a more viscous liquid, for the same configuration of reservoir, wick and heater, for example. A higher viscosity liquid with higher surface tension may be more difficult to vaporise, since more energy is required to drive vapour from the portion of liquid at the vaporise. A higher level of power may therefore be required at the vaporiser to create a same amount of vapour. This applies also to changes in specific heat capacity and vaporisation temperature that may occur if the liquid composition is changed; a higher or lower amount of power may be needed to deliver enough heat energy to raise the liquid at the vaporiser to its vaporisation temperature.

[0103] From this it will be apparent that even relatively small changes to the recipe can change the vaporisation behaviour of a liquid. If this is not taken into account, a typical liquid range made available to consumers for use with a particular type or design of aerosol provision system, for example as pre-filled reservoirs or cartridges, will demonstrate potentially significant differences in vaporisation behaviour. Use of a single equation across the range of liquid types to estimate liquid consumption as described above will therefore likely be inaccurate in at least some cases. The proposal herein that the recipe or composition of a liquid be modified in order that the liquid demonstrates a vaporisation behaviour the same as that for a specified liquid used to derive the equation aims to address this matter.

[0104] Clearly, there is substantial scope for modifying the composition of a liquid compared to the specified liquid in such a way that the vaporisation behaviour is altered to match the specified liquid. Some options are discussed below, but the disclosure is not limited in this way, and it will be apparent to the skilled person that the composition can be modified in any way appropriate to achieve the desired effect (possibly within boundaries set by legislation, for example, to limit the maximum nicotine content of commercially supplied liquids). At the same time, the ability to offer different liquid types that retain choice of nicotine level, flavour and experience for the user is important.

[0105] A significant characteristic that can vary between types of liquid is the taste / flavour, determining the flavouring experienced by the user when inhaling the aerosol. User expectation is for a variety of flavours of liquid to be available. The composition of the first liquid type may therefore include one or more different flavourings (flavouring components) from the specified liquid type. Different flavouring components may have different properties that cause a change in vaporisation behaviour of the liquid if one flavouring is replaced with another. Also, in some cases, a different amount of a flavouring component may be needed to produce a stronger or weaker flavour experience. In this case, the proportion of the flavouring component in the liquid changes, requiring or producing a corresponding change in the proportion of one or more other components which could alter the vaporisation behaviour. If these effects are present, the overall composition of the liquid can be modified by changing the proportion(s) of one or more other components while retaining the required flavouring contribution, in order to match the vaporisation behaviour to that of the specified liquid.

[0106] Another significant characteristic that can vary between types of liquid is the nicotine level or strength, where the nicotine may be present as nicotine only or as a nicotine salt, which offer different experiences of nicotine delivery to the user. User expectation is for a variety of nicotine levels to be available. The composition of the first liquid type may therefore include a different amount or proportion of nicotine from the specified liquid type. The nicotine content of a liquid is typically given in units of mg / ml, thereby indicating how much nicotine is present per millilitre of the liquid. Accordingly, to provide a higher or level amount of nicotine may require a larger or smaller volume of nicotine to be included in the liquid, which will alter the proportion of nicotine to the other ingredients and change the overall composition of the liquid. Hence, the vaporisation behaviour may be altered. Indeed, it may be found that changing the nicotine level has a greater effect on the vaporisation behaviour than changing the flavour of the liquid. If this effect is present, the overall composition of the liquid may again be modified by changing the proportion(s) of one or more other components while retaining the required nicotine amount, in order to match the vaporisation behaviour to that of the specified liquid. In other cases, the concentration of nicotine in the nicotine component might be changed so that a same proportion of the nicotine component can be used while still changing the amount of nicotine, thereby allowing the proportions of the other ingredients to be retained, which may preserve the same vaporisation behaviour.

[0107] As noted above, the viscosity of the liquid can make a significant contribution to vaporisation behaviour. Hence, it may be found that matching the viscosity of the first liquid to that of the specified liquid may be appropriate to provide a same vaporisation behaviour. For example, if a change of flavouring component or an increase or decrease in nicotine as compared with the specified liquid results in a change in viscosity, the PG:VG ratio might be adjusted slightly up or down to compensate and make the viscosity the same as of the specified liquid. A more viscous flavouring component will increase the overall viscosity of the liquid, which might be compensated by increasing the amount of PG and decreasing the amount of VG (increasing the PG:VG ratio), for example. In another example, a higher nicotine level might require a larger proportion of nicotine, reducing the overall viscosity, and being compensable by decreasing the PG:VG ratio so that a higher proportion of VG is used, providing more viscosity.

[0108] Hence, in some examples, the first liquid type differs from the specified liquid type by having a different PG:VG ratio from that of the specified liquid. This may be additionally or alternatively to the viscosity of the first liquid type and the specified liquid type being the same.

[0109] In other cases, it may desirable to maintain the PG:VG to be the same for the first liquid type and the specified liquid type. As noted above, many liquids include equal amounts of PG and VG (often described as a PG:VG ratio of 50:50, where this indicates that the proportion of each in the total amount of PG and VG within the liquid is 50%, and does not indicate that either makes up 50% of the whole of the liquid), as this is considered to provide a good compromise between the different characteristics imparted by each of these components. Hence, it may be desirable to offer multiple liquids all having the same PG:VG ratio, but differing in other ways such as by flavour or nicotine level. The composition of the first liquid might be modified in various ways to achieve this, such as by including a further ingredient such as water, or by changing the total combined amount of PG and VG in the liquid while maintaining the proportions of PG and VG within the total amount.

[0110] In the foregoing, the term “same” has been used when comparing the first liquid type and the specified liquid type, for example that the vaporisation behaviour and the aerosol mass per puff are the same, or various proportions of components in the liquids are the same. This is not intended to be limited to exact parity only, but to also include substantially the same, similar and substantially similar to the extent that the equation is able to deliver a useful level of accuracy of estimation of liquid amount in the reservoir.

[0111] Figure 10 shows a flow chart of steps in a third example method for estimating a liquid amount in an aerosol provision system, generally in line with features of the preceding disclosure of the second example of compensation. The method may be performed by a controller comprised within an aerosol provision system, such as within a device component of an aerosol provision system that can be coupled to a cartridge or pod component to form the complete aerosol provision system. In a first step S1 B, a power level value is obtained, being a level of power which is applied a vaporiser of the aerosol provision system during a puff taken by a user of the aerosol provision system. The vaporiser operates under the supply of electrical power to generate aerosol for the puff by vaporising liquid from the reservoir. In this example, liquid in the reservoir is a first liquid type. The aerosol provision system includes a modification compared to a specified aerosol provision system that vaporises liquid of a specified type which is different from the first liquid type. The modification is implemented to compensate for differences in vaporisation behaviour that may arise between liquids of different types if this is not taken into account. Specifically, the modification comprises a composition of the first liquid type, which is modified compared with a composition of the specified liquid type in order to provide a same vaporisation behaviour for both liquid types. In a second step S2B (noting that steps S1 B and S2B may be reversed in order or carried out simultaneously), a puff duration value is obtained, being a duration of the puff for which the power at the obtained power level value has been applied to the vaporiser. Once the power level value and the puff duration value have been obtained, the method proceeds to step S3B, in which a mass of aerosol in the puff is determined from the power level value and the puff duration value. The mass of aerosol is determined using an equation relating power level and puff duration to mass of aerosol which is a function fitted to empirical data from measurements of mass of aerosol generated during puffs of known puff duration value at known power level value previously made on a population of aerosol provision systems with the same type or configuration of vaporiser and vaporising the specified liquid type. Once the mass of aerosol in the puff has been determined, the method proceeds to step S4B, in which an estimation is made of an amount of liquid in the reservoir, using the determined mass of aerosol and a known amount of liquid that was in the reservoir prior to the puff.

[0112] The third example noted above, in which compensation of the vaporisation behaviour is achieved by modification of a configuration of the vaporiser, will now be described in more detail.

[0113] More specifically, it is contemplated herein that the vaporiser of the aerosol provision system, in terms of its configuration, design and / or performance, be modified in order to compensate for a different vaporisation behaviour of the liquid of the first type in the reservoir as compared to the specified liquid type. The vaporiser is modified compared to the configuration of the vaporiser in the specified aerosol provision system, which may be referred to as the specified configuration of vaporiser, the specified vaporiser or simply the specified configuration. For example, the vaporiser may be modified in order to deliver a different amount of heat energy than the specified vaporiser for the same level of power supplied to it to cause vaporisation of the liquid. This modification can be utilised when the vaporiser comprises an electrical heating element, for instance.

[0114] Since the first liquid type and the specified liquid type exhibit different vaporisation behaviours, an aim in achieving liquid amount estimation accuracy via an equation derived for the specified liquid type is to enable the two liquid types to produce a same aerosol mass in a puff for the same puff duration and same power level applied to the vaporiser. This makes the available equation equally applicable to the first liquid type. Since the vaporisation behaviours are fixed, and the puff duration and power level supplied by the controller to the vaporiser are under the user’s choice (or fixed in systems with no power level adjustment), the configuration of the vaporiser becomes a variable that can be modified to achieve matching of the aerosol masses. If the first liquid type vaporises more rapidly or at a lower temperature, the vaporiser can be modified so that it reaches a lower temperature in the course of a puff or outputs less heat energy than the vaporiser in the specified aerosol provision system for the same applied power level. If the first liquid type vaporises more slowly or at a higher temperature, the vaporiser can be modified so that it reaches a higher temperature in the course of a puff or outputs more heat energy than the vaporiser in the specified aerosol provision system for the same applied power level.

[0115] Hence, it is proposed that the vaporiser is modified such that the heat energy it produces for vaporisation of liquid of the first type provided to it from the reservoir in the aerosol provision system is selected such that the mass of aerosol generated in a puff with a given puff duration value and a given power level value is the same or substantially the same as the mass of aerosol generated in a puff with the same puff duration value and the same power level value by the specified vaporiser vaporising liquid of the specified type. Since the specified vaporiser and the specified type of liquid are used in collecting the empirical data to obtain the equation for determining the mass of aerosol in a puff, this is effectively equivalent to modifying the vaporiser so that the mass of aerosol generated in a puff with a given puff duration value and a given power level value is the same or substantially the same as the mass of aerosol which is determined using the equation with the given puff duration value and the given power level value.

[0116] An electrical heating element converts electrical energy into heat energy. The passage of electric current through an electrically resistive component (resistor) generates heat, via the process of Joule heating. In the context of an aerosol provision system, an electrical heating element has aerosolisable substrate material, which in the current context is a liquid, provided on or near its surface, such as by a wick carrying liquid from the reservoir to the environs of the heating element. A selected amount of electrical power is applied to the heating element from the battery under control of the controller so that current flows through the heating element and heat is generated. This heat energy transfers to the adjacent liquid which is heated in turn to its vaporisation temperature and vapour is produced. Air flowing over or past the heating element collects the vapour so that aerosol is formed and delivered to the user for inhalation. As the vapour is removed by the flowing air, it is replaced by vaporisation of further liquid delivered to the heating element, thereby maintaining aerosol production for the time that power continues to be supplied to the heating element to generate the heat energy.

[0117] The electrical resistance of the heating element is the property that allows the conversion of the applied electrical energy to heat energy, according to the equation P = I2R, where P is the amount of applied electrical power lost or converted to heat, I is the electrical current in amps, and R is the electrical resistance in ohms. Since power is defined as energy per time, the heat energy Q produced by the heating element is Q = I2R t, where t is time in seconds. Hence, the amount of heat energy produced for a given value of current can be altered by changing the resistance of the heating element. In the present context, the electrical current is not available as a variable because we want to utilise the values of electrical power supplied to the vaporiser in a manner consistent with the equation, so that the controller is able to use the equation to estimate remaining liquid amounts even though a different liquid is being used.

[0118] Accordingly, a way to modify the vaporiser in order to compensate for different liquid types is to alter the electrical resistance. In this way, the amount of heat energy for a given level of power supplied to the vaporiser for a given puff duration can be varied up or down to ensure that the aerosol mass produced by the vaporiser in that puff generated from the first liquid is substantially the same as the aerosol mass produced by the specified vaporiser in an equivalent puff generated from the specified liquid.

[0119] If the first liquid has a lower rate of vaporisation or a higher vaporisation temperature than the specified liquid, the vaporiser may be modified by increasing its resistance. This will cause the vaporiser to output more heat energy so that the first liquid is heated and vaporised more rapidly and the aerosol mass produced in a puff of given duration is increased. If the first liquid has a higher rate of vaporisation or a lower vaporisation temperature than the specified liquid, the vaporiser may be modified by decreasing its resistance. This will cause the vaporiser to output less heat energy so the first liquid is heated and vaporised less rapidly and the aerosol mass produced in a puff of given duration is decreased. Hence, the aerosol mass per puff can be adjusted up or down to match the first liquid to the specified liquid, and thereby compensate for differences in vaporisation behaviour.

[0120] The electrical resistance R of a resistor, such as an electrical heating element, is given by R = p I / A, where p is the electrical resistivity of the material from which the resistor is made (and indicates the ability of that material to resist the flow of electrical current), I is the length of the resistor, and A is the cross-sectional area of the resistor.

[0121] Hence, the three variables of electrical resistivity, length and cross-sectional area are available for modifying a vaporiser to give it a different electrical resistance and hence heat energy output compared to the specified vaporiser.

[0122] If a vaporiser comprises an electrical heating element, the electrical heating element may be connected directly to receive the electrical power supplied from the battery under control of the controller, or distinct electrical connections may be provided between the electrical heating element and the battery. In the latter case, if the electrical connections and the electrical heating element are together considered to comprise the vaporiser, both the electrical connections and the heating element are available for modification of the vaporiser’s electrical resistance. In the former case, the electrical heating element alone is available for modification of the vaporiser’s electrical resistance. Hence, in some examples the electrical heating element has a different electrical resistance from the electrical resistance of the electrical heating element in the specified vaporiser configuration to provide the modification. In other examples, electrical connections of the electrical heating element may have a different electrical resistance from the electrical resistance of electrical connections of the electrical heating element in the specified vaporiser configuration to provide the modification. In still other examples, the overall design or configuration of the vaporiser may differ from the specified configuration in order to achieve a different electrical resistance. For example, one of the vaporiser and the specified vaporiser may include distinct electrical connections, while in the other, distinct electrical connections are omitted. A common configuration for an electrical heating element of a vaporiser in an aerosol provision system is a wire coil, formed by winding conductive metallic wire into a helix or spiral shape. The coil may be wound around a generally cylindrical wick formed from a bundle of fibres or a rod of a porous material such as porous ceramic, for example. These examples are not limiting, however. A heating element structured as a coil may be readily modified to alter its electrical resistance in order to change its heat energy output as described above. The material from which the wire is made that is formed into the coil may be varied, for example. Metals and metal alloys can vary significantly in their electrical resistivity, so can be selected accordingly, although various metallic materials are more or less suitable for use in forming vaporisers as the skilled person is aware. An example material which is widely used is nickelchromium alloy, or NiCr, a family of alloys which can be formed from different proportions of nickel and chromium, providing a way to adjust resistance by varying the alloy composition. Other metals are not excluded, however.

[0123] Resistance of a wire coil may also be modified by changing the thickness or diameter of the wire. This changes the cross-sectional area A of the heating element, which as explained above, will alter the electrical resistance. A thicker wire provides a large cross- sectional area and a lower electrical resistance, and a thinner wire provides a smaller crosssection area and a higher electrical resistance.

[0124] The length I of the heating element can also be changed to modify the electrical resistance, again as explained above.

[0125] Figure 11A shows a simplified schematic side view of an example wire coil electrical heating element vaporiser (in which the wick, and connection to the battery are omitted for clarity). In this example, the coil 42 has an overall spatial length L, and comprises five loops or turns of wire with a pitch or spacing s. The actual length I of wire, which determines the electrical resistance, is around all the spiral path of the loops, and is therefore greater than the spatial length L. This may the specified vaporiser configuration, for example. The wire length I can be readily increased or decreased to increase or decrease the electrical resistance of the heating element by increasing or decreasing the number of loops. This can be done in alternative ways. A first way is to change the spacing s of the loops. This may be useful in that the spatial length L of the heating element can be kept the same as that of the specified configuration, so that the modified heating element can be readily installed in an aerosol provision system without the need for other design changes. Figure 11 B shows a coil heating element 42 with a same spatial length L as the specified design, but having a decreased spacing s’ between the coil loops. This allows more loops to be accommodated with the spatial length L, in this case 8, so that the wire length I is increased, and the resistance of the heating element is modified upwards. Similarly, if the spacing between the coil loops is increased, fewer loops can be accommodated in the spatial length L, the wire length I is decreased and the resistance of the heating element is modified downwards.

[0126] A second way to modify the wire length is to keep the spacing s the same as in the specified configuration, and to alter the spatial length L of the heating element to accommodate more or fewer loops of wire. This may be preferred if it is found that a wider or closer loop spacing has an unwanted effect on vaporisation (since the heat energy density delivered to the wick will be changed), but it will be necessary to ensure that different spatial sizes of heating element can be installed in the specified aerosol provision system, with suitable adjustments being made if necessary. Figure 11C shows an example coil heating element 42 with the same coil spacing s as the specified design, and a reduced wire length I (and corresponding reduced electrical resistance) compared to the specified design, by reducing the number of loops and thereby giving a shorter spatial length L’, less than L. Figure 11 D shows an example coil heating element 42 with the same coil spacing s as the specified design, and an increased wire length I (and corresponding increased electrical resistance) compared to the specified design, by increasing the number of loops and thereby given a longer spatial length L”, greater than L.

[0127] Figure 12A shows a simplified schematic example of a vaporiser comprising a heating element and distinct electrical connections for electrically coupling the heating element to the battery (not shown) of the aerosol provision system. The electrical heating element 44 is shown schematically only and may take a wire coil form as in the Figures 11 A-11 D examples, or may have an alternate format as will be apparent to the skilled person. Two electrical connections 45 are provided, conductively coupled to opposite ends of the electrical heating element 45 to enable current flow through the electrical heating element under the supply of power from the battery, and shown as being substantially straight. The electrical connections may be wires, stamped metal shapes, printed conductive traces or any other arrangement apparent to the skilled person. The vaporiser has a spatial dimension H (which can be thought of as height for convenience) and may be considered as the specified vaporiser configuration.

[0128] As noted above, an option for modifying electrical resistance of a vaporiser is to modify the electrical resistance of electrical connections 45 of an electrical heating element 44. As with the wire coil examples, electrical resistance of the electrical connections 45 can be altered by using a different electrically conductive material that has a different electrical resistivity p. Similarly, the electrical resistance of the electrical connections 45 can be altered by changing the cross-sectional area A of the electrical connections 45, such as be using a thinner or thicker wire. In other examples, the length of one or both of the electrical connections 45 may be altered to modify the electrical resistance of the vaporiser.

[0129] Figure 12B shows an example of a vaporiser modified compared to the specified vaporiser of Figure 12A by increasing the length of the electrical connections 45 so as to increase the electrical resistance. In order to maintain the spatial height H of the vaporiser to be the same as that for the specified vaporiser so that the modified vaporiser can be more easily used in an aerosol provision system without the need for other design changes, in this example the electrical connections 45 have shaped portions which may be bends, angles, curves or coils introduced within the length I of the electrical connections 45 while the overall spatial length (end-to-end separation) of the electrical connections is kept the same. Figure 12C shows an alternative example in which the length I of the electrical connections 45 is increased; in this example the electrical connections 45 are kept straight so that the spatial height H’ of the vaporiser is increased to greater than the height H of the specified configuration. Conversely, Figure 12D shows an example in which the length I of the electrical connections 45 is reduced to provide a lower electrical resistance. The electrical connections are straight, giving a spatial height of the vaporiser H” which is decreased to less than the height H of the specified configuration.

[0130] Figures 13A and 13B show simplified schematic representations of example vaporisers according to another example. As with the Figures 12A - 12D examples, it is proposed that the electrical resistance of the vaporisers is modified by changing the resistance offered in the electrical connections 45 of the electrical heating element 45. In this example, however, one or more separate resistors or resistive elements (a single element being shown for simplicity) be included within one or both of the electrical connections 45. Figure 13A shows a first resistive element 46 having a first value of resistance R, and Figure 13B shows a second resistive element 46’ having a second value of resistance R’ which is different from R. The resistive elements may be conventional electrical resistors which are readily available with a wide range of resistance values, or may be an inserted portion of an electrical conductor of a different material, length and / or thickness.

[0131] As noted above, a variety of different formats are commonly employed to implement the heating effect in a vaporiser of an aerosol provision system. An example is a conductive mesh or grid or similar, configured to perform both as an electrical heating element and to provide a wicking or capillary function to draw liquid from the reservoir to be heated and vaporised. This functionality can be provided by any configuration which is both conductive and porous, although in terms of shape such a vaporous is commonly planar to enable ready escape of vapour into the air flow path. Examples include a woven structure of metallic wires, a planar element formed from sintered or welded metallic wires, and a perforated metal sheet.

[0132] Figure 14A shows a simplified plan view of a first example vaporiser of this type. The planar element 48 has an elongate rectangular shape and is shown with fine cross-hatching to indicate a first structure offering a first value of electrical resistance R. Electrical connections are omitted for simplicity, but are typically located at opposite ends of the elongate shape to provide a long electrical current path to maximise resistance and therefore also the heating effect, for efficient vaporisation. Figure 14B shows a simplified plan view of a second example vaporiser of this type, with a coarser cross-hatching to indicate a second structure offering a second value of electrical resistance R’ which is different from R. The resistance may be modified in a variety of ways by changing the structure of the element. Different conductive materials may be used. The size of the pores in the porous structure may be changed to offer a different total amount of conductive material in order to change the cross-sectional area of the current path. The thickness of wire used to make the porous structure may be changed. Alternatively, if it is convenient that the external dimensions of the planar element be altered, its overall length or width can be changed, to change the overall resistor length or cross- sectional area.

[0133] The various techniques for modifying the resistance of a vaporiser described above may be used alone or in combination, as will be apparent to the skilled person. Moreover, other approaches not described in detail but offering the same effect are not excluded.

[0134] Figure 15 shows a flow chart of steps in a fourth example method for estimating a liquid amount in an aerosol provision system, generally in line with features of the preceding disclosure of the third example of compensation. The method may be performed by a controller comprised within an aerosol provision system, such as within a device component of an aerosol provision system that can be coupled to a cartridge or pod component to form the complete aerosol provision system. In a first step S1C, a power level value is obtained, being a level of power which is applied a vaporiser of the aerosol provision system during a puff taken by a user of the aerosol provision system. The vaporiser operates under the supply of electrical power to generate aerosol for the puff by vaporising liquid from the reservoir. In this example, liquid in the reservoir is a first liquid type. The aerosol provision system includes a modification compared to a specified aerosol provision system that vaporises liquid of a specified type which is different from the first liquid type. The modification is implemented to compensate for a difference in vaporisation behaviour between the liquid of the first type and the liquid of the specified type. Specifically, the modification comprises a difference in the configuration of the vaporiser of the aerosol provision system compared to a configuration of a specified vaporiser in the specified aerosol provision system. The modification causes the vaporiser to deliver a different amount of heat energy for vaporising the first liquid. In a second step S2C (noting that steps S1C and S2C may be reversed in order or carried out simultaneously), a puff duration value is obtained, being a duration of the puff for which the power at the obtained power level value has been applied to the vaporiser. Once the power level value and the puff duration value have been obtained, the method proceeds to step S3C, in which a mass of aerosol in the puff is determined from the power level value and the puff duration value. The mass of aerosol is determined using an equation relating power level and puff duration to mass of aerosol which is a function fitted to empirical data from measurements of mass of aerosol generated during puffs of known puff duration value at known power level value previously made on a population of aerosol provision systems with the specified configuration of vaporiser and vaporising the specified liquid type. Once the mass of aerosol in the puff has been determined, the method proceeds to step S4C, in which an estimation is made of an amount of liquid in the reservoir, using the determined mass of aerosol and a known amount of liquid that was in the reservoir prior to the puff.

[0135] The fourth example noted above, in which compensation of the vaporisation behaviour is achieved by modification of a configuration of the air flow path, will now be described in more detail.

[0136] More specifically, it is contemplated herein that an airflow path in the aerosol provision system in which the vaporiser is located, in terms of its configuration, design and / or performance, by modified in order to compensate for a different vaporisation behaviour of the liquid of the first type in the reservoir as compared to the specified liquid type. The air flow path is modified compared to the configuration of the air flow path in the specified aerosol provision system, which may be referred to as the specified configuration of air flow path, the specified air flow path, or simply the specified configuration.

[0137] The aerosol mass in a puff depends in part on the rate at which vapour produced by the vaporiser is picked up by air flowing past the vaporiser and entrained as aerosol delivered to the user for inhalation. A larger volume of air or a faster air flow speed may collect more vapour for a given puff duration than a smaller volume of air or a slower air flow speed. Hence, if the first liquid type vaporises rapidly there is the potential that a large amount of vapour can be converted to aerosol during a puff if there is sufficient air flow to carry the vapour away from the vaporiser as rapidly as it is generated. In such a case, decreasing the amount of air flow past the vaporiser during a puff will reduce the mass of aerosol in a puff. If the first liquid type vaporises more slowly so that a smaller amount of vapour is available during a puff to create aerosol, increasing the amount of air flowing past the vaporiser during a puff will collect the vapour and carry it away from the vaporiser more efficiently and allow more vapour and more aerosol to be produced so that the mass of aerosol in a puff is increased. Accordingly, the mass of aerosol for a given power level and puff duration produced from the first liquid can be adjusted up or down to match or approximately match the mass of aerosol for the same power level and puff duration produced from the specified liquid in the specified aerosol provision system. The amount or speed of air flow can be altered by modifying the configuration or structure of the air flow path in the aerosol provision system in which the vaporiser is located.

[0138] Since the first liquid type and the specified liquid type exhibit different vaporisation behaviours, an aim in achieving liquid amount estimation accuracy via an equation derived for the specified liquid type is to enable the two liquid types to produce a same aerosol mass in a puff for the same puff duration and same power level applied to the vaporiser. This makes the available equation equally applicable to the first liquid type. Since the vaporisation behaviours are fixed, and the puff duration and power level supplied by the controller to the vaporiser are under the user’s choice (or fixed in systems with no power level adjustment), the configuration of the air flow path, and hence the amount or volume of air that collects vapour from the vaporiser over the course of a puff of a particular duration, becomes a variable that can be modified to achieve matching of the aerosol masses.

[0139] Hence, it is proposed that the air flow path is modified such that the amount of air collecting vapour from liquid of the first type provided to the vaporiser from the reservoir in the aerosol provision system is selected such that the mass of aerosol generated in a puff with a given puff duration value and a given power level value is the same or substantially the same as the mass of aerosol generated in a puff with the same puff duration value and the same power level value by the specified air flow path with a same or similar type of vaporiser vaporising liquid of the specified type. Since the specified air flow path and the specified type of liquid are used in collecting the empirical data to obtain the equation for determining the mass of aerosol in a puff, this is effectively equivalent to modifying the air flow path so that the mass of aerosol generated in a puff with a given puff duration value and a given power level value is the same or substantially the same as the mass of aerosol which is determined using the equation with the given puff duration value and the given power level value.

[0140] Figure 16 shows a highly simplified schematic and not-to-scale longitudinal cross- sectional representation of an example aerosol provision system, for the purpose of illustrating relevant features for air flow path modification as described herein. The aerosol provision system 10 is depicted with many parts not shown, for simplicity and ease of understanding, but should be understood as potentially including some or all of the parts and features described with regard to Figures 1 and 5. The aerosol provision system 10 has an outer housing 50, through which an air flow path runs, and which otherwise accommodates the parts and features of the aerosol provision system that enable aerosol provision. The air flow path extends between an air inlet 26, which is shown as a small opening in a side wall of the housing 50, but which may be located elsewhere, or may comprise more than one opening, and an aerosol outlet 56 in a mouthpiece part 35 of the aerosol provision system 10. The air flow path comprises an upstream part 52 that carries air from the air inlet 26 to a vaporisation chamber 54. The vaporisation chamber 54 has a vaporiser 7 located in it, that operates as previously described to deliver heat energy to liquid delivered to the vaporiser 7 from a reservoir (not shown) by a liquid supply arrangement such as a wick or other porous member (not shown), when supplied with electrical power from a battery (not shown) under the control of a controller (not shown). The configuration of the vaporiser 7 is not limited, and may take any convenient form. In some examples, the vaporiser will comprise an electrical heating element. The upstream part 52 of the air flow channel terminates in a chamber inlet 53 at an upstream side of the vaporisation chamber 54, through which air passes from the upstream part 52 to enter the vaporisation chamber 54. The vaporisation chamber 54 provides an intermediate part of the air flow channel. A chamber outlet 58 at the downstream side of the vaporisation chamber 54 forms the start of a downstream part 55 of the air flow channel, which extends from the chamber outlet 58 to the aerosol outlet 56 in the mouthpiece 35. The air flow channel is hence made up of the upstream part 52 (being upstream of the vaporiser 7), the vaporisation chamber 54, and the downstream part 55 (being downstream of the vaporiser 7).

[0141] When a user inhales on the aerosol provision system 10 through the aerosol outlet 56, air A enters the air inlet 26 and flows along the upstream part 52 and into the vaporisation chamber 54. In the vaporisation chamber 54, the air A flows over, around and past the vaporiser 7 and collects or picks up vapour V generated by the vaporiser 7 and present in the region around the vaporiser 7. The air A and the entrained vapour V carried by it form an aerosol, which flows out of the vaporisation chamber 54 via the chamber outlet 58 and along the downstream part 55, to provide a puff of aerosol 60 to the user. From this it can be appreciated that, for a given puff duration and a given amount of power driving the vaporiser (so that it reaches a particular temperature to heat the liquid for vaporisation, for example), the form of the air flow past the vaporiser 7 is a factor that determines how much aerosol is present in the puff, in other words, the aerosol mass in the puff. Assuming that the heat energy given out by the vaporiser 7 to heat the liquid is sufficient to maintain vaporisation and the supply of liquid is maintained, vaporisation continues to occur over the course of a puff while the flowing air collects already-formed vapour and carries it out of the vaporisation chamber. Newly formed vapour replaced collected vapour as the puff proceeds. Hence, the total amount of aerosol in the puff can depend on the volume of air that passes over the vaporiser 7 during the puff in appropriate proximity to collect vapour. If a larger or smaller total volume of air is caused to pass over the vaporiser within the puff, more or less aerosol is included in the puff. Therefore, the aerosol mass in a puff can be altered by changing the flow of air along the air flow path, which can be achieved by modifying the configuration of the air flow path. In particular, the air flow path can be modified, compared to a specified configuration, upstream of the vaporiser, in order to provide a different air flow past the vaporiser (in terms of air flow velocity or total amount or volume of air, for example) In this way, the aerosol mass in a puff of given duration and given applied power for a first liquid in the reservoir of the aerosol provision system can be adjusted to match the aerosol mass in a puff of the given duration and given applied power for the specified liquid in the reservoir of the specified aerosol provision system (which may have a vaporiser of the same type as the vaporiser in the aerosol provision system), in order that the equation determined from ACM data of the specified liquid in the specified aerosol provision system can be used by the aerosol provision system to estimate liquid consumption and remaining liquid amount of the first liquid type. The example of Figure 16 shows an air flow path in which the upstream part 52 and the downstream part 55 are narrower (they have a smaller cross-sectional area or areas, being the area perpendicular to the direction of air flow along the path) than the vaporisation chamber 54 between them. The air flow path broadens after the chamber inlet 53 and forms a space or cavity in which the vaporiser 7 is located, of sufficient size to accommodate the vaporiser and allow adequate air flow over and past and the vaporiser 7; this is the vaporisation chamber 54. After the chamber outlet 58, the air flow path narrows. This is purely an example, however, and the air flow path may take any form able to carry air from the air inlet to the vaporiser and aerosol from the vaporiser to the aerosol outlet. For example, the vaporisation chamber may have a substantially similar width to the upstream part or the downstream part or both, and the upstream part and / or the downstream part may include narrowings or widenings or bends or other features. The shape of the vaporisation chamber 54 is also an example only. The vaporisation chamber may take any form, shape or size able to accommodate the vaporiser and the flowing air, and having regard to its relationship with other components present within the housing of the aerosol provision system. The factor of interest is that a feature or features of the air flow path (broadly, the configuration of the air flow path), in which the vaporiser is located, is modified compared to the specified configuration of air flow path, to adjust the air flow and the aerosol mass in a puff.

[0142] One way in which the air flow past the vaporiser may be modified is to change the speed or velocity of the air as it passes over the vaporiser. Air moving more quickly will be able, for a given puff duration, to collect more vapour and increase the aerosol mass (provided the vapour production rate keeps pace with vapour removal so that new vapour is available for collection), while air moving more slowly will collect less vapour during the same puff duration and decrease the aerosol mass. Bernoulli’s principle can be utilised to achieve this. Bernoulli’s principle governs the relationship between velocity and pressure for a flowing fluid. In accordance with the principle, a reduction in the cross-sectional area of a fluid flow channel causes an increase in flow velocity, and an increase in the cross-sectional area causes a decrease in flow velocity. This can be used to change the velocity of the air moving through the air flow channel and past the vaporiser. One way to implement this is to modify the cross- sectional area of the air flow channel at or near the chamber inlet through which the air enters the vaporisation chamber.

[0143] Figure 17A shows a simplified schematic longitudinal cross-sectional view of an example vaporisation chamber 54 in which a vaporiser 7 is located, as before. An upstream part 52 of the air flow channel delivers air into the vaporisation chamber 7 through the chamber inlet 53. For the purpose of illustration, consider that this example is the specified configuration of the air flow channel in the aerosol provision system type used to collect ACM data for deriving the equation. The chamber inlet 53 has a specified width Ws, giving a particular cross- sectional area to the air flow channel at the point. Air entering with vaporisation chamber 54 therefore has a particular air flow velocity vs defined by the specified width Ws. The greater cross-sectional area of the vaporisation chamber 54, owing to its larger width, will cause the air flow velocity to reduce within the vaporisation chamber, but the width Ws of the chamber inlet will at least in part determine the air flow velocity past the vaporiser 7, when the air is collecting vapour.

[0144] Figure 17B shows a simplified schematic longitudinal cross-sectional view of an example air flow channel and vaporisation chamber modified compared to the specified configuration of Figure 17A. The upstream part 52 of the air flow channel has a width W1 at or near the chamber inlet 53 which is larger than the specified width Ws, so that the chamber inlet 53 has a larger cross-sectional area than in the specified air flow channel. The vaporisation chamber 54 has substantially the same dimensions as the vaporisation chamber in the specified configuration. The larger chamber inlet 53 produces a slower air flow velocity v1 for air entering the vaporisation chamber 54, which is less than vs, and the otherwise same design for the vaporisation chamber 54 means that the air flow velocity past the vaporiser 7 is reduced compared to the airflow velocity past the vaporiser in the specified configuration. The flowing air therefore has less opportunity to collect vapour over the course of a puff. If the liquid used has a vaporisation behaviour with a higher vaporisation rate than the specified liquid type, the reduced volume of air passing the vaporiser can be selected to collect an amount of vapour that gives a same aerosol mass in the puff as the specified liquid in the specified air flow channel configuration. Hence, the difference in vaporisation behaviour can be compensated.

[0145] Figure 17C shows an example in which the upstream part of the air flow channel has a width W2 at or near the chamber inlet 53 which is larger than the specified width Ws, so that the chamber inlet 53 has a smaller cross-sectional area than in the specified air flow channel. This produces a faster air flow velocity v2 for air entering the vaporisation chamber 54, which is higher than vs, so that the air flow velocity over the vaporiser 7 is increased compared to the air flow velocity past the vaporiser in the specified configuration. Hence a larger volume of air can pass the vaporiser 7 during a puff. If the liquid used has a vaporisation behaviour with a lower vaporisation rate than the specified liquid type, the increased volume of air passing the vaporiser can be selected to collect an amount of vapour that gives a same aerosol mass in the puff as the specified liquid in the specified air flow channel configuration. Hence, the difference in vaporisation behaviour can again be compensated.

[0146] In these examples, the width of the upstream part of the air flow channel can be modified (increased or reduced) compared to the specified design over the whole length of the upstream part, or for a portion immediately upstream of the chamber inlet, or at the chamber inlet only. Alternatively or additionally, a cross-sectional area modification might be implemented within the vaporisation chamber itself. Any modification which produces a change in the air flow velocity past the vaporiser can be used.

[0147] The structural modifications of the Figures 17B and 17C examples could be relatively detailed to implement, since walls defining the air flow channel and / or the vaporisation chamber require alteration. An alternative that may be considered simpler is to utilise an insert placed into the chamber inlet to reduce its cross sectional area.

[0148] Figure 18 shows a simplified schematic longitudinal cross-sectional view of an example air flow channel and vaporisation chamber modified compared to a specified configuration, by use of an insert. An upstream part 52 of the air flow channel at the chamber outlet 53 has a width Ws and corresponding cross-sectional area that matches the width and cross-sectional area in the specified configuration. In order to modify the air flow velocity in the vaporisation 54 and past the vaporiser 7, an annular insert 56 with a central aperture is placed inside the air flow channel at the chamber inlet 53. The central aperture has a width W which is less than the specified width Ws. The insert 56 therefore provides a constriction in or narrowing of the air flow channel at or near the chamber inlet 53 which reduces the cross-sectional area and causes an increase in the air flow velocity entering the vaporisation chamber, so that for an otherwise same vaporisation chamber, the air flow velocity past the vaporiser is increased, to compensate for a different liquid vaporisation behaviour and achieve a same aerosol mass in a puff. While an annular or similar insert with an aperture within it, such as is shown in Figure 8, may be convenient to be anchored or placed securely within the chamber inlet, an insert or other restricting element that provides an obstacle to narrow the airflow path around less than its whole perimeter may alternatively be used.

[0149] The use of an insert of this kind to modify the air flow channel can only provide a decrease in the cross-sectional area and a corresponding increase in air flow velocity. This form of modification can therefore only compensate for liquid types which have a lower vaporisation rate or otherwise produce vapour less rapidly or produce an otherwise smaller amount of vapour than the specified liquid type. Accordingly, when collecting the ACM data from which the equation is derived, it is useful to use a specified liquid type which has a high vaporisation rate and / or produces vapour rapidly or otherwise in large quantity, so that other liquid types likely to provided within aerosol provision systems to end users are likely to produce less vapour and therefore be able to be compensated successfully. Inserts that provide different amounts of reduction in the air flow channel cross-sectional area (such as by having central apertures of different widths) can be used to increase the air flow velocity past the vaporiser by different amounts, and thereby compensate for a variety of first types of liquid having vaporisation behaviours different from one another.

[0150] Another way in which the air flow past the vaporiser may be modified is to change the volume or amount of air adjacent to the vaporiser at any given time. This can be considered as providing a similar effect to changing the air flow velocity, in that over the course of a puff a larger or smaller total amount of volume of air moves past the vaporiser and is made available to collect vapour, so that the aerosol mass in the puff can be adjusted up or down. As an example, this modification can be implemented by changing the volume of the vaporisation chamber.

[0151] Figure 19A shows a simplified schematic longitudinal cross-sectional view of an example vaporisation chamber 54 in which a vaporiser 7 is located, as before. An upstream part 52 of the air flow channel delivers air into the vaporisation chamber 7 through the chamber inlet 53. For the purpose of illustration, consider that this example is the specified configuration of the air flow channel in the aerosol provision system type used to collect ACM data for deriving the equation. The vaporisation chamber 54 has a specified width or height Xs, with a corresponding specified total volume or capacity for containing air. This volume will, to some extent, govern the total amount of air which the user is able to draw through the air flow channel over the course of a puff, and which is therefore available to collect vapour from the vaporiser 7 during the puff.

[0152] Figure 19B shows a simplified schematic longitudinal cross-sectional view of an example air flow channel and vaporisation chamber modified compared to the specified configuration of Figure 19A. The vaporisation chamber 54 has a width or height X1 which is greater than the width Xs of the vaporisation chamber in the specified configuration, giving a correspondingly larger air capacity to the vaporisation chamber 54. Hence, the air flow channel can accommodate more air, and a larger amount of air can be drawn past the vaporiser 7 over the course of a puff of a given duration, compared to the specified configuration. Therefore, more air is available to collect vapour during the puff, and the aerosol mass for a first liquid type can be increased. If the liquid used has a vaporisation behaviour that produces a lower amount of vapour than the specified liquid type, the increased amount of air passing the vaporiser provides increased effectiveness in collecting the available vapour and can be selected to collect an amount of vapour that gives a same aerosol mass in the puff as the specified liquid in the specified air flow channel configuration. In other cases, the first liquid type may have a vaporisation behaviour that produces a different aerosol droplet size so that the vapour collection process differs and a different aerosol mass results if the same amount of air is used; changing the available air volume can hence alter the aerosol mass. Hence, the difference in vaporisation behaviour between the first and specified liquid types can be compensated. This modification will depend to some extent on the dispersion of the vapour from the vaporiser 7 since the ability of flowing air to collect vapour may reduce with distance from the vaporiser 7; hence there may be a maximum width of the vaporisation chamber beyond which further increase does not improve vapour collection. Note also that the change in width of the air flow channel caused by the larger vaporisation chamber may alter the air flow velocity so this may need to be also taken into account.

[0153] Figure 19C shows an example in which the vaporisation chamber 54 has a width or height X2 which is smaller than the specified width Xs, so that the vaporisation chamber has a reduced air capacity compared to the specified configuration. A smaller amount of air will be drawn past the vaporiser 7 over the course of a puff of a given duration, compared to the specified configuration, so that less air is available to collect vapour during the puff, and the aerosol mass for a first liquid type can be reduced. If the liquid used has a vaporisation behaviour that produces a higher amount of vapour or a more efficient vapour collection process than the specified liquid type, the reduced amount of air passing the vaporiser provides reduced effectiveness in collecting the available vapour and can be selected to collect an amount of vapour that gives a same aerosol mass in the puff as the specified liquid in the specified air flow channel configuration. Again, the difference in vaporisation behaviour between the first and specified liquid types can be compensated.

[0154] A further way in which the air flow past the vaporiser may be modified is to change the level of turbulence in the flow of air through the vaporisation chamber. Turbulence can increase the circulation of air in the vicinity of the vaporiser so that a larger proportion of the flowing air is brought into contact with vapour as it is generated from the vaporiser. The efficiency of vapour collection can be increased. Hence, an increased amount of vapour may be collected during a puff so that the aerosol mass in the puff is increased. A reduced turbulence gives a smoother, less disrupted air flow so that a lower proportion of the flowing air is likely to collect vapour, and the efficiency of vapour collection is reduced. A lower amount of vapour may be collected during a puff so that the aerosol mass in the puff is reduced. Therefore, an air flow pathway structure modified to provide a more turbulent air flow past the vaporiser can compensate a first liquid type with a vaporisation behaviour that results in less vapour / aerosol (such as a lower vaporisation rate) than the specified liquid, by collecting the available vapour more effectively. An air flow pathway structure modified to provide a less turbulent air flow past the vaporiser can compensate a first liquid type with a vaporisation behaviour that results in more vapour / aerosol (such as a higher vaporisation rate) than the specified liquid, by collecting the available vapour less effectively.

[0155] A turbulent air flow can be provided by introducing one or more obstacles into the air flow path. Obstacles within the vaporisation chamber and therefore near to the vaporiser may be most effective at changing the level of turbulence around the vaporiser so that the effect on vapour collection is more pronounced. Obstacles can be implemented by shaping the side walls of the air flow channel, particularly the walls defining the vaporisation chamber, so that there are parts which protrude or extend into the bore of the air flow path and hence interact with or impede the forward movement of air along the air flow path. Therefore, in some examples, the modification to the configuration of the air flow channel can be broadly described as providing a different shape for the vaporisation chamber.

[0156] Figure 20 shows a simplified schematic longitudinal cross-sectional view of an example air flow channel and vaporisation chamber modified to disrupt the air flow in a turbulent manner. As before, a vaporiser 7 is located in a vaporisation chamber 54, and an upstream part 52 of the air flow channel delivers air into the vaporisation chamber 7 through a chamber inlet 53, the vaporisation chamber 54 having a chamber outlet 58 leading to the downstream part 55 of the airflow channel. A plurality of fins 57 are provided which protrude inwardly from the side walls defining the vaporisation chamber, into the interior space of the vaporisation chamber 54, on either side of (or indeed all around) the vaporiser 7). Air entering the vaporisation chamber 54 and moving through it impacts on the fins 57 and is diverted, creating turbulent air flow around the vaporiser 7 so that the air is able to collect more of the vapour generated by the vaporiser 7 than may be case in the absence of the fins 57. The example is not limited to the depicted configuration, and any modification able to alter the amount of turbulence might be used. Also, shaping in the form of protrusions of other shapes and placed in different locations within the vaporisation chamber 54 may alternatively be used to provide a greater or lesser amount of turbulent air flow around the vaporiser. In order the simplify the modification of the air flow path to appropriately compensate for the particular first liquid type in any particular aerosol provision system, obstacles or protruding parts might be formatted as an insert that can be placed into the vaporisation chamber during fabrication. Different sizes, shapes and / or numbers of protruding parts might be added to address a range of different first liquid types. Shaping might also be provided in the upstream part 52 of the air flow path in order to impart some turbulence to the flowing air before it enters the vaporisation chamber 54. For example, side walls of the upstream part might be provided with spiral grooves (rifling) in order to produce a spiralling air flow in the vaporisation chamber.

[0157] Additionally or alternatively, the vaporiser itself might be shaped so as to provide a greater or lesser amount of turbulence in the air flowing over it. For example, if the vaporiser comprises an electric heating element that has a generally planar shape, the planar element might be formed in a corrugated shape so as to provide a bumpy surface over which the air will pass. The size and or number of corrugations could be chosen to select a suitable level of disruption to the air flow. Providing obstacles actually on the vaporiser itself may be efficient in that the turbulence can be focussed in the region immediately around the vaporiser where the generated vapour will be most dense.

[0158] Note that in the foregoing description, mention of higher and lower, or increased and decreased, larger and smaller amounts of vapour, vapour collection and aerosol mass, and similar terms is intended to indicate higher and lower (etc.) relative to the performance for the first liquid type in the absence of modification to the air flow path. The modification causes an increase or decrease compared to the unmodified configuration (being the specified configuration) with the aim of making the aerosol mass in a puff the same in the modified configuration for the first liquid as in the specified configuration for the specified liquid.

[0159] At a high level, the above concepts can be broadly summarised as, within an aerosol provision system, a configuration of the air flow path is modified to alter the efficiency of the collection of vapour from the vaporiser by air flowing in the air path containing the vaporiser, in order to adjust an aerosol mass in a puff of defined puff duration, for the purpose of compensating for a difference in vaporisation behaviour of the liquid being vaporised, being of a first type, compared to the vaporisation behaviour of liquid of a specified type as vaporised in an aerosol provision system with a vaporiser in an air flow path of a specified (unmodified) configuration.

[0160] Accordingly, modifications to the airflow path are not limited to the particular examples described above; rather any modification that alters the air flow in such a way as to provide the required compensation for different liquid type vaporisation behaviour can be implemented. For example, any of the various approaches described above may be combined with one another in any combination.

[0161] Figure 21 shows a flow chart of steps in a fifth example method for estimating a liquid amount in an aerosol provision system, generally in line with features of the preceding disclosure of the fourth example of compensation. The method may be performed by a controller comprised within an aerosol provision system, such as within a device component of an aerosol provision system that can be coupled to a cartridge or pod component to form the complete aerosol provision system. In a first step S1 D, a power level value is obtained, being a level of power which is applied a vaporiser of the aerosol provision system during a puff taken by a user of the aerosol provision system. The vaporiser is located in an air flow path through the aerosol provision system and operates under the supply of electrical power to generate aerosol for the puff by vaporising liquid from the reservoir. In this example, liquid in the reservoir is a first liquid type. The aerosol provision system includes a modification compared to a specified aerosol provision system that vaporises liquid of a specified type which is different from the first liquid type. The modification is implemented to compensate for a difference in vaporisation behaviour between the liquid of the first type and the liquid of the specified type. Specifically, the modification comprises a difference in the configuration of the air flow path in which the vaporiser of the aerosol provision system is located, compared to a specified configuration of an air flow path in the specified aerosol provision system. The modification causes the a difference in air flow over or past the vaporiser for collection of vapour formed from the first liquid. In a second step S2D (noting that steps S1 D and S2D may be reversed in order or carried out simultaneously), a puff duration value is obtained, being a duration of the puff for which the power at the obtained power level value has been applied to the vaporiser. Once the power level value and the puff duration value have been obtained, the method proceeds to step S3D, in which a mass of aerosol in the puff is determined from the power level value and the puff duration value. The mass of aerosol is determined using an equation relating power level and puff duration to mass of aerosol which is a function fitted to empirical data from measurements of mass of aerosol generated during puffs of known puff duration value at known power level value previously made on a population of aerosol provision systems with the specified configuration of air flow path and vaporising the specified liquid type. Once the mass of aerosol in the puff has been determined, the method proceeds to step S4D, in which an estimation is made of an amount of liquid in the reservoir, using the determined mass of aerosol and a known amount of liquid that was in the reservoir prior to the puff.

[0162] In conclusion, in order to address various issues and advance the art, this disclosure shows by way of illustration various embodiments in which the claimed invention(s) may be practiced. The advantages and features of the disclosure are of a representative sample of embodiments only, and are not exhaustive and / or exclusive. They are presented only to assist in understanding and to teach the claimed invention(s). It is to be understood that advantages, embodiments, examples, functions, features, structures, and / or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the scope of the claims. Various embodiments may suitably comprise, consist of, or consist essentially of, various combinations of the disclosed elements, components, features, parts, steps, means, etc. other than those specifically described herein. The disclosure may include other inventions not presently claimed, but which may be claimed in future.

Claims

Claims1 . An aerosol provision system comprising: a reservoir holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for a specified aerosol provision system vaporising liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein a feature of the aerosol provision system is modified compared to the specified aerosol provision system to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

2. An aerosol provision system according to claim 1 , wherein the feature of the aerosol provision system comprises an initial amount of the first liquid in the reservoir, a composition of the first liquid, a configuration of the vaporiser, or a configuration of an air flow path in which the vaporiser is located.

3. An aerosol provision system according to claim 1 or claim 2, wherein the equation has been obtained by fitting to empirical data from measurements of mass of aerosol generated during puffs with known puff duration value and known power level value made on a population of the specified aerosol provision systems with liquid of the specified liquid type.

4. An aerosol provision system comprising: a reservoir holding an initial volume of liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using anequation relating power level and puff duration to mass of aerosol for an aerosol provision system with a same type of vaporiser and a reservoir holding a specified initial volume of liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the initial volume of the liquid of the first type in the reservoir is modified compared to the specified initial volume to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

5. An aerosol provision system according to claim 4, wherein the initial volume of the liquid of the first type is selected to be N times the specified initial volume, where N is the proportion of the mass of aerosol generated by the vaporiser in a puff having a given puff duration value and a given power level value using the first liquid compared to the mass of aerosol determined using the equation with the given puff duration value and the given power level value.

6. An aerosol provision system according to claim 4 or claim 5, wherein N is less than 1 or equal to 1.

7. An aerosol provision system according to claim 4 or claim 5, wherein N is greater than 1.

8. An aerosol provision system according to any one of claims 4 to 7, wherein the equation has been obtained by fitting to empirical data from measurements of mass of aerosol generated during puffs with known puff duration value and known power level value made on a population of aerosol provision systems or cartridges therefor with the same type of vaporiser and with liquid of the specified liquid type and the specified initial volume.

9. An aerosol provision system according to any one of claims 1 to 8, wherein the equation is obtained by linear fitting to the empirical data.

10. An aerosol provision system according to any one of claims 1 to 8, wherein the equation is obtained by nonlinear fitting to the empirical data.

11. An aerosol provision system according to any one of claims 1 to 10, wherein the controller stores the equation, and is configured to determine the mass of aerosol for the puff by calculating the mass of aerosol using the equation.

12. An aerosol provision system according to any one of claims 1 to 10, wherein the controller stores a look-up table constructed using the equation which maps power level values or ranges of power level values and puff duration values or ranges of puff duration vales to mass of aerosol values, and is configured to determine the mass of aerosol for a puff using the look-up table.

13. An aerosol provision system according to any preceding claim, wherein the controller is further configured to obtain the power level value and the puff duration value.

14. A method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for a specified aerosol provision system vaporising liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein a feature of the aerosol provision system has been modified compared to the specified aerosol provision system to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

15. A method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding an initial volume of liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff;determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system or cartridge therefor with a same type of vaporiser and a reservoir holding a specified initial volume of liquid of a specified liquid type different from the first liquid type; and estimating an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the initial volume of the liquid of the first type in the reservoir has been modified compared to the specified initial volume in order to compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

16. An aerosol provision system comprising: a reservoir holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system with a same type of vaporiser and with liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein a composition of the first liquid type is modified compared to the specified liquid type such that the first liquid type has a same vaporisation behaviour as the specified liquid type.

17. An aerosol provision system according to claim 16, wherein the composition of the first liquid type is selected such that a mass of aerosol generated by the vaporiser in a puff having a given puff duration value and a given power level value using the first liquid type is the same as the mass of aerosol determined using the equation with the given puff duration value and the given power level value.

18. An aerosol provision system according to claim 16 or claim 17 wherein the composition of the first liquid type includes a different proportion of nicotine from the specified liquid type.

19. An aerosol provision system according to any one of claims 16 to 18, wherein the composition of the first liquid type includes a different flavouring or flavourings from the specified liquid type.

20. An aerosol provision system according to any one of claims 16 to 19, wherein the first liquid type has a different composition but a same viscosity as the specified liquid type.21 . An aerosol provision system according to any one of claims 16 to 20, wherein the first liquid type has a different ratio of propylene glycol to vegetable glycerine from the specified liquid type.

22. An aerosol provision system according to any one of claims 16 to 20, wherein the first liquid type has a same ratio of propylene glycol to vegetable glycerine from the specified liquid type.

23. An aerosol provision system according to any one of claims 16 to 22, wherein the equation has been obtained by fitting to empirical data from measurements of mass of aerosol generated during puffs with known puff duration value and known power level value made on a population of aerosol provision systems with the same type of vaporiser and with liquid of the specified liquid type.

24. An aerosol provision system according to any one of claims 16 to 23, wherein the equation is obtained by linear fitting to the empirical data.

25. An aerosol provision system according to any one of claims 16 to 23, wherein the equation is obtained by nonlinear fitting to the empirical data.

26. An aerosol provision system according to any one of claims 16 to 25, wherein the controller stores the equation, and is configured to determine the mass of aerosol for the puff by calculating the mass of aerosol using the equation.

27. An aerosol provision system according to any one of claims 16 to 25, wherein the controller stores a look-up table constructed using the equation which maps power level values or ranges of power level values and puff duration values or ranges of puff duration vales to mass of aerosol values, and is configured to determine the mass of aerosol for a puff using the look-up table.

28. An aerosol provision system according to any one of claims 16 to 27, wherein the controller is further configured to obtain the power level value and the puff duration value.

29. An aerosol provision system according to any one of claims 16 to 28, further comprising an indicator for indicating to the user an amount of liquid in the reservoir, wherein the controller is configured to operate the indicator to indicate the estimated amount of liquid in the reservoir.

30. A method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system or cartridge therefor with a same type of vaporiser and with liquid of a specified liquid type different from the first liquid type; and estimating an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the first liquid type has a composition which is modified compared to the specified liquid type such that the first liquid type has a same vaporisation behaviour as the specified liquid type.

31. An aerosol provision system comprising: a reservoir holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system with a specified configuration of vaporiser and with liquid of a specified liquid type different from the first liquid type; andestimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the vaporiser is modified compared to the specified configuration in order to deliver a different amount of heat energy for vaporising the liquid from the level of power supplied and thereby compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

32. An aerosol provision system according to claim 31 , wherein the different amount of heat energy is selected such that a mass of aerosol generated by the vaporiser in a puff having a given puff duration value and a given power level value using the first liquid is the same as the mass of aerosol determined using the equation with the given puff duration value and the given power level value.

33. An aerosol provision system according to claim 31 or claim 32, wherein the vaporiser is modified by having a different electrical resistance from the specified configuration.

34. An aerosol provision system according to any one of claims 31 to 33, wherein the vaporiser comprises an electrical heating element.

35. An aerosol provision system according to claim 34, wherein the electrical heating element has a different electrical resistance from the specified configuration.

36. An aerosol provision system according to claim 34, wherein one or more electrical connections of the electrical heating element have a different electrical resistance from the specified configuration.

37. An aerosol provision system according to claim 34, comprising one or more resistors in series with the electrical heating element and having a different electrical resistance from the specified configuration.

38. An aerosol provision system according to any one of claims 31 to 37, wherein the equation has been obtained by fitting to empirical data from measurements of mass of aerosol generated during puffs with known puff duration value and known power level value made on a population of aerosol provision systems with the specified configuration of vaporiser and with liquid of the specified liquid type.

39. An aerosol provision system according to any one of claims 31 to 38, wherein the equation is obtained by linear fitting to the empirical data.

40. An aerosol provision system according to any one of claims 31 to 38, wherein the equation is obtained by nonlinear fitting to the empirical data.

41. An aerosol provision system according to any one of claims 31 to 40, wherein the controller stores the equation, and is configured to determine the mass of aerosol for the puff by calculating the mass of aerosol using the equation.

42. An aerosol provision system according to any one of claims 31 to 40, wherein the controller stores a look-up table constructed using the equation which maps power level values or ranges of power level values and puff duration values or ranges of puff duration vales to mass of aerosol values, and is configured to determine the mass of aerosol for a puff using the look-up table.

43. An aerosol provision system according to any one of claims 31 to 42, wherein the controller is further configured to obtain the power level value and the puff duration value.

44. An aerosol provision system according to any one of claims 31 to 43, further comprising an indicator for indicating to the user an amount of liquid in the reservoir, wherein the controller is configured to operate the indicator to indicate the estimated amount of liquid in the reservoir.

45. A method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system or cartridge therefor with a specified configuration of vaporiser and with liquid of a specified liquid type different from the first liquid type; andestimating an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the vaporiser has been modified compared to the specified configuration in order to deliver a different amount of heat energy for vaporising the liquid from the level of power supplied and thereby compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

46. An aerosol provision system comprising: a reservoir holding liquid to be vaporised, the liquid being of a first liquid type; a vaporiser for vaporising liquid from the reservoir; the vaporiser located in an air flow path; and a controller configured to: determine a mass of aerosol generated by the vaporiser during a puff taken by a user, from a power level value indicating a level of power supplied to the vaporiser during the puff and a puff duration value indicating a duration of the puff, and using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system with a vaporiser located in a specified configuration of air flow path and with liquid of a specified liquid type different from the first liquid type; and estimate an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the air flow path is modified compared to the specified configuration in order to provide a different air flow past the vaporiser and thereby compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.

47. An aerosol provision system according to claim 46, wherein the different air flow past the vaporiser is selected such that a mass of aerosol generated by the vaporiser in a puff having a given puff duration value and a given power level value using the first liquid is the same as the mass of aerosol determined using the equation with the given puff duration value and the given power level value.

48. An aerosol provision system according to claim 46 or claim 47, wherein the air flow path is modified to provide a different volume of air flow past the vaporiser for a given puff duration value.

49. An aerosol provision system according to claim 46 or claim 47, wherein the air flow path is modified to provide a different velocity of air flow past the vaporiser.

50. An aerosol provision system according to claim 46 or claim 47, wherein the air flow path is modified by comprising a different volume of a chamber in which the vaporiser is located.

51. An aerosol provision system according to claim 46 or claim 47, wherein the air flow path is modified by comprising a different shape of a chamber in which the vaporiser is located.

52. An aerosol provision system according to any one of claims 46 to 51 , wherein the vaporiser comprises an electrical heating element.

53. An aerosol provision system according to any one of claims 46 to 52, wherein the equation has been obtained by fitting to empirical data from measurements of mass of aerosol generated during puffs with known puff duration value and known power level value made on a population of aerosol provision systems with the same type of vaporiser located the specified configuration of air flow path and with liquid of the specified liquid type.

54. An aerosol provision system according to any one of claims 46 to 53, wherein the equation is obtained by linear fitting to the empirical data.

55. An aerosol provision system according to any one of claims 46 to 53, wherein the equation is obtained by nonlinear fitting to the empirical data.

56. An aerosol provision system according to any one of claims 46 to 55, wherein the controller stores the equation, and is configured to determine the mass of aerosol for the puff by calculating the mass of aerosol using the equation.

57. An aerosol provision system according to any one of claims 46 to 55, wherein the controller stores a look-up table constructed using the equation which maps power level values or ranges of power level values and puff duration values or ranges of puff duration vales to mass of aerosol values, and is configured to determine the mass of aerosol for a puff using the look-up table.

58. An aerosol provision system according to any one of claims 46 to 57, wherein the controller is further configured to obtain the power level value and the puff duration value.

59. An aerosol provision system according to any one of claims 46 to 58, further comprising an indicator for indicating to the user an amount of liquid in the reservoir, wherein the controller is configured to operate the indicator to indicate the estimated amount of liquid in the reservoir.

60. A method for estimating a liquid amount in an aerosol provision system, the method comprising: obtaining a power level value indicating a level of power applied to a vaporiser of the aerosol provision system during a puff taken by a user, the vaporiser located in an airflow path and configured to generate aerosol by vaporising liquid from a reservoir of the aerosol provision system, the reservoir holding liquid of a first liquid type; obtaining a puff duration value indicating a duration of the puff; determining a mass of aerosol generated by the vaporiser during the puff, from the power level value and the puff duration value, using an equation relating power level and puff duration to mass of aerosol for an aerosol provision system or cartridge therefor with a vaporiser located in a specified configuration of air flow path and with liquid of a specified liquid type different from the first liquid type; and estimating an amount of liquid in the reservoir after the puff by using the determined mass of aerosol and a known amount of liquid in the reservoir prior to the puff; wherein the air flow path has been modified compared to the specified configuration in order to provide a different air flow past the vaporiser and thereby compensate for a difference in vaporisation behaviour of the first liquid type compared to the specified liquid type.