ELECTRONIC CIGARETTE

Description

Background of the invention

[0001] The invention lies in the general field of electronic cigarettes comprising a heating element capable of vaporizing a substrate in response to inhalations by the user, when the heating element is powered.

[0002] More specifically, the invention proposes a solution to allow estimation of the quantity of substrate vaporized by the heating element.

[0003] We know of solutions which aim to estimate this quantity by measuring the variation in the resistivity of the heating element when the temperature of this heating element varies due to inhalations.

[0004] Document EP 2 468 116 describes in particular a solution of this type in which the resistivity of a heating element is calculated from the potential difference across the terminals of that element.

[0005] Document EP 2 143 346 A1 describes in particular a flow sensor system for detecting the flow of a fluid indicating a puff in an aerosol-generating system.

[0006] US document 2003 / 033055 A1 discloses a method and device for vaporizing a liquid.

[0007] Unfortunately, the variation in the resistivity of the heating element is very difficult to measure, so these solutions do not allow for an accurate estimation of the amount of substrate vaporized. Object and summary of the invention

[0008] According to a first aspect, the invention relates to an electronic cigarette as presented in the attached set of claims.

[0009] In this document, the concept of "vaporization" is to be taken in a broad sense; it refers to the transformation of the substrate into gas, including at a temperature below 100°C. Brief description of the drawings

[0010] Other features and advantages of the present invention will become apparent from the description below, with reference to the accompanying drawings, which illustrate an example of an embodiment without being limiting in any way. In these figures: there figure 1 represents a first embodiment of an electronic cigarette conforming to the invention; the figure 2 represents the voltage variation across different components of the electronic cigarette. figure 1 following inhalation; the figure 3 represents the theoretical difference between the output voltages of two RC circuits of the figure 1 , in the absence of inhalation; the figure 4 illustrates a method for calculating inhalation intensity in an electronic cigarette. figure 1 there figure 5 represents details of an electronic cigarette conforming to a second embodiment of the invention; the figure 6depicts details of an electronic cigarette according to an example that is not part of the invention; the figure 7 illustrates a method for calculating inhalation intensity in an electronic cigarette. figure 6 ; and the figure 8 depicts details of an electronic cigarette according to an example that is not part of the invention; the figure 9 represents, in the form of a flowchart, the main steps of an estimation process according to an example which is not part of the invention. Detailed description of a first embodiment of the invention

[0011] We will now describe, with reference to the figure 1 a first embodiment of an electronic cigarette 1 according to the invention, figure in which only the electronic components useful for understanding this embodiment have been represented.

[0012] The electronic cigarette 1 includes a heating element 10 capable of vaporizing a substrate, the resistivity R10(t) of this heating element being likely to vary according to its temperature.

[0013] In this embodiment, the heating element 10 has a first unreferenced terminal connected to ground and a second terminal A, so that the potential U10 of this terminal corresponds to the voltage across the terminals of the heating element 10.

[0014] According to the invention, the electronic cigarette 1 includes a battery 3 capable of delivering a voltage U0, and a switch 5 connected to a terminal P of the battery, to power, only when the user presses a button not shown, the heating element 10 from the battery 3.

[0015] In the embodiment described here, the voltage U0 has a nominal voltage of the order of 3.7V and a discharge curve in a range [4.2V, 0V].

[0016] When the switch 5 is in the closed position, an electric current of intensity i passes through this switch and an electric current of intensity i10 passes through the heating element 10.

[0017] In order to measure the variations in the voltage U10(t) across the heating element 10, the electronic cigarette 1, in this embodiment, includes a measuring resistor R connected in series between a terminal Q of the switch 5 and the terminal A of the heating element 10. The measuring resistor carries an electric current of intensity i when the switch 5 is in the closed position. The intrinsic characteristics of the measuring resistor R are not affected by inhalation.

[0018] Due to this particular arrangement, and considering that switch 5 is a perfect switch (i.e., lossless, therefore with U5 = U0), we obtain, in a known manner: U 10 t = U 0 ⋅ R 10 t / R + R 10 t

[0019] Therefore, variations in the resistivity R10(t) of the heating element 10 are accompanied by a variation in the voltage U10(t) across the terminals of the heating element.

[0020] There figure 2 represents on the ordinate the voltage U10(t) across the terminals of the heating element 10 as a function of time, a figure on which four events occurring at times t1 to t4 have been represented: t1: The button closing switch 5 is pressed. The voltage U10(t) across the heating element 10, which was zero, almost instantaneously reaches a voltage very close to the voltage U0 of battery 3. From this instant t1 onward, and as long as the user does not inhale, the temperature of the heating element 10 increases until it reaches a limiting temperature, its resistivity R10(t) increases, and the voltage U10(t) increases. t2 and t3: Inhalation begins and ends. Inhalation brings a flow of cold air onto the heating element 10, which lowers its temperature, decreases its resistivity R10(t), and therefore lowers the voltage U10(t) across its terminals. Conversely, the end of inhalation, if switch 5 remains closed, causes the heating element to heat up and the voltage across its terminals to increase.t4: release of the button and opening of switch 5: the heating element 10 is no longer powered by the battery 3 and the voltage U10(t) across its terminals returns to zero almost instantaneously.

[0021] In this document, the term "smoking period" refers to the time period between times t1 and t4, namely the period during which the user presses the button controlling switch 5 in the closed position. During this period, the user may not inhale or may inhale one or more puffs.

[0022] In this first particular embodiment of the invention, the quantity of substrate vaporized during a smoking period is estimated by comparing a measurement ΔU10 mes (t) of an approximation of the variation of the voltage U10(t) across the terminals of the heating element 10 during this smoking period with a theoretical estimate ΔU10 TH (t) of this approximation of this voltage variation in the absence of any inhalation during the smoking period.

[0023] More specifically, in this embodiment of the invention, the difference between two voltages U11(t) and U12(t) measured at the terminals B1, B2 of a circuit 500 comprising two distinct and identical type sub-circuits 11, 12 is chosen as an approximation of the voltage variation at time t across the heating element 10. The voltages U11(t) and U12(t) across this circuit 500 are approximations of the voltage U10(t) across the heating element 10 at two slightly different times.

[0024] It is fundamental to note that none of the components of the 500 circuit have an intrinsic characteristic that is disrupted by inhalations.

[0025] In the embodiment described here, two series RC sub-circuits 11,12 are used, placed in series between the heating element 10 and calculation means 30 capable of calculating the difference between the voltages U11(t) and U12(t).

[0026] In the embodiment described here, the voltages U11(t) and U12(t) are the potentials of points B and C shown in the figure 1 .

[0027] The time constant T12 of the second RC 12 circuit is chosen to be much greater than that T11 of the first RC 11 circuit, for example by a factor of 100.

[0028] In the embodiment described here, an amplifier 20 of gain G is used to amplify the difference ΔU10(t) between U11(t) and U12(t).

[0029] In the embodiment described here, the resistances R11 and R12 of the sub-circuits RC 11 and 12 are negligible compared to the impedance of the amplifier 20.

[0030] Therefore, ΔU 10 t = G ⋅ U 12 t − U 11 t

[0031] In the embodiment described here: the gain G is chosen in the range [100 ; 10000], for example equal to 500; the difference U12(t) - U11(t) is on the order of a few tens of microvolts; and ΔU10(t) is on the order of a few tens or even hundreds of microvolts and measurable by the means of calculation 30.

[0032] On the figure 2 We have also represented the output voltages U11(t) and U12(t) of the series RC subcircuits 11 and 12.

[0033] As explained previously, when the user presses the button at time t1, the heating element 10 is powered and the voltage U10(t) across it increases. The two capacitances C11, C12 of the RC subcircuits 11, 12 charge, with the second and larger capacitance C12 lagging behind the first and smaller capacitance 11. Consequently, between pressing the button (t1) and the start of inhalation (t2), U12(t) <U11 (t)<U10(t).

[0034] When the user begins to inhale at time t2, the heating element 10 cools down and the voltage U10(t) across its terminals decreases. The second and larger capacitance C12 lags behind the first and smaller capacitance C11. Throughout the inhalation period, between t2 and t3, U12(t) > U11(t) > U10(t).

[0035] When the user stops inhaling at time t3, the heating element 10 heats up and the voltage U10(t) across its terminals increases. We then return to the situation in which U12(t) <U11(t)<U10(t).

[0036] Shortly after the user releases the button at time t4, the voltage U10(t) becomes zero again, the capacitors C11 and C12 discharge and their output voltages U11(t), U12(t) become zero again.

[0037] As is known, when a constant voltage is applied across the terminals of a capacitor, there is a transient regime during which the capacitor gradually charges until it reaches a limit charge that depends on its value, and a steady-state regime during which the charge of the capacitor remains at this limit value as long as this constant voltage continues to be applied to it.

[0038] There figure 2 This corresponds to the situation in which the user begins to inhale (time t2) in steady state. Those skilled in the art will understand that if the user began to inhale during the transient state, with the large capacitor C12 not fully charged, the output voltage U12(t) of the second capacitor would not necessarily become greater than the output voltage U11(t) of the first capacitor.

[0039] In the embodiment described here, the system formed by the two sub-circuits 11 and 12 is in transient regime for about 800 ms after the instant t1 when the user presses the button.

[0040] There figure 3 , which represents the theoretical difference ΔU10 TH (t) between the output voltages U11(t) and U12(t) of the two RC sub-circuits 11, 12 in the absence of inhalation, in other words a theoretical approximation of the variation of the voltage U10(t) across the heating element 10 at time t, illustrates these different regimes.

[0041] During the transient regime, U12(t) is always less than U11(t), but as shown in the figure 2 the absolute value of the difference between these two voltages increases then decreases until it reaches a constant value α in steady state.

[0042] In the embodiment described here, this constant α can be neglected and assumed to be zero thereafter.

[0043] In a transitional regime, and noting: R11, the resistance of the first series 11 RC sub-circuit; C11, the capacitance of the first series 11 RC sub-circuit; R12, the resistance of the second series 12 RC sub-circuit; C12, the capacitance of the second series 12 RC sub-circuit; T11 the time constant R1.C1 of the first series 11 RC sub-circuit; and T12 the time constant R2.C2 of the second series 12 RC sub-circuit; Theoretically, we obtain: U11THt=U10t.1−exp−t / T11 U12THt=U11THt.1−exp−t / T12 i.e.U12THt=U10t.1−exp−t / T11.I−exp−t / T12

[0044] Therefore, the theoretical variation ΔU10 TH (t) of the voltage across the heating element 10 is expressed as: ΔU 10 TH t = G ⋅ U 11 TH t − U 12 TH t soit ΔU 10 TH t = G ⋅ U 10 t . 1 − exp − t / T 11 . exp − t / T 12 or with (1) ΔU 10 TH t = G . U 0 . R 10 t / R + R 10 t . 1 − exp − t / T 11 − exp − t / T 12

[0045] By making the approximation that R10(t) is constant during the smoking period and equal to R10(t1), we finally obtain the expression for ΔU10 TH (t): in a transitional phase: ΔU 10 TH t = G . U 0 . R 10 t 1 / R + R 10 t 1 . 1 − exp − t / T 11 − exp − t / T 12 in steady state: ΔU 10 TH t = α = 0 .

[0046] In the implementation of the figure 1 , the approximation ΔU10 MES (t) of the variation of the voltage U10(t) across the heating element 10 is the output voltage of the amplification means 20, namely the potential of terminal 9.

[0047] In the embodiment described here, the quantity of substrate vaporized during a smoking period is estimated from an inhalation intensity F calculated by integrating the difference during a smoking period, between the approximation ΔU10 MES (t) of the variation of the voltage U10(t) across the heating element 10 during this smoking period and the theoretical estimate ΔU10 TH (t) of this approximation of this voltage variation in the absence of any inhalation during the smoking period.

[0048] This inhalation intensity F corresponds, in the example embodiment described here, to the shaded area Figure 4 This area can notably be calculated by a Riemann sum with a step of 20ms between times t2 and t4.

[0049] In the implementation example described here, t2 is determined to be the instant when the absolute value of the difference ΔU10 MES (t) and ΔU10 TH (t) becomes greater than a predetermined threshold S T2: Δ U 10 MES t 2 − Δ U 10 TH t 2 > S T 2

[0050] Time t4 is the moment when the user releases the button.

[0051] To calculate the inhalation intensity F using the Riemann method, ΔU10 MES (t) and ΔU10 TH (t) are evaluated and stored at different times between t1 and t4, for example every 20 ms. In this embodiment: 1. ΔU10 MES (t) is the measurement of the potential at terminal 9 at time t. 2. ΔU10 TH (t) between t1 and t1+800ms (transient regime) is read from a recording in a first database BD1, constructed during preliminary laboratory tests and stored in the electronic cigarette 1. The recording is selected according to the parameters of equation (2). 3. ΔU10 TH (t) = 0, between t1+800ms and t4 (steady-state regime).

[0052] Returning to equation (2), the expression for ΔU10 TH (t) in transient regime depends on six parameters, namely: the gain G of amplifier 20; the voltage U0 delivered by battery 3; the resistivity R10(t1) of the heating element assumed constant; the value of the measurement resistance R; the time constants T11 and T12 of the RC sub-circuits 11 and 12.

[0053] In the embodiment described here, and returning to the figure 1, the computing means 30 are capable of measuring the voltage U0 at terminal P of battery 3 by means of a voltage probe 6.

[0054] In the embodiment described here, the calculation means 30 are also capable of estimating the resistivity R10(t1) of the heating element. To do this, the calculation means 30 measure, at time t1, the voltages U5 at terminal Q of the switch 5 using a voltage probe 7 and the voltage U10 at terminal A of the heating element 10 using a voltage probe 8.

[0055] Denoting i as the intensity of the electronic current that passes through the resistance R, we obtain by applying the node law to the terminal A, and Ohm's law to the resistance R, we obtain i1 + i10 = (U5 - U10) / R.

[0056] However, in the embodiment described here, it is negligible compared to i10. Therefore, by applying Ohm's law to the heating element 10: R 10 = R . U 10 / U 5 − U 10

[0057] In the embodiment of the invention described herein, the first database BD1 stores, for a plurality of six-tuples corresponding to the 6 parameters {G, U0, R10, R, T11, T12}, values ​​of the theoretical voltage ΔU10 TH (t) in the absence of inhalation and in transient regime at different times t counted between t1 and t1+800ms.

[0058] The computing resources are therefore able to calculate the inhalation intensity F using the Riemann method.

[0059] In the embodiment described here, the computing means 30 query a second database BD2 of the electronic cigarette 1 to determine the quantity of substrate vaporized during the smoking period as a function of four parameters: duration t4 - t1 of the smoking period; voltage U0 of the battery 3 measured by the calculation means 30; resistance R10(t1) of the heating element 10, assumed constant during a smoking period, and measured by the calculation means 30; and inhalation intensity F, calculated here by the Riemann method.

[0060] Alternatively, other parameters can also be used, including the temperature of the heating element 10 at t1, the viscosity of the substrate, the evaporation rate of the substrate, the heat transfer function of the heating element 10 characterizing its cooling, the density of vaporized substrate droplets as a function of the inhalation intensity F, ...

[0061] In the embodiment described here, the voltage U0 of the battery 3 is measured by the computing means 30. Alternatively, this voltage could be considered constant and equal to the nominal value of the battery. Description of a second embodiment of the invention

[0062] In the implementation of the figure 1 , we use 2 series RC subcircuits 11, 12 in series and an amplifier 20 to estimate the voltage variation ΔU10(t) across the terminals of the heating element 10.

[0063] Alternatively, and as shown in the figure 5 For example, we can use a 500 circuit comprising three RC sub-circuits and two amplifiers 201, 202.

[0064] In this embodiment: The first RC sub-circuit (R11 / C11) closely follows the voltage across the heating element R10 and represents an estimate of the voltage across the heating element R10(t) at time t of the measurement; the second RC sub-circuit (R12 / C12) follows with a slight delay dt the voltage across the heating element R10 and represents an estimate of what the voltage R10(t-dt) across the heating element R10 was at a time t-dt close to time t of the measurement; the third RC sub-circuit (R13 / C13) follows with a greater delay Dt the voltage across the heating element R10 and represents an estimate of what the voltage R10(t-Dt) across the heating element R10 was at a time t-Dt further from time t of the measurement.

[0065] To this end, the time constants of the three RC sub-circuits are chosen so that the equation below is verified: R 11 . C 11 < R 12 . C 12 < R 13 . C 13 ;

[0066] Furthermore, for more precise monitoring, it may be more optimal to also have the following equation verified: R 11 . C 11 / R 12 . C 12 < R 12 . C 12 / R 13 . C 13

[0067] None of the components of the 500 circuit have an intrinsic characteristic that is disturbed by inhalations.

[0068] In this embodiment, the 500 circuit has four terminals B1, B2, B3 and B4.

[0069] As in the first embodiment, the quantity of substrate vaporized during a smoking period is estimated from an inhalation intensity F calculated by integrating the difference during a smoking period, between the approximation of the variation of the voltage U10(t) across the heating element 10 during this smoking period and the theoretical estimate ΔU10 TH (t) of this approximation of this voltage variation in the absence of any inhalation during the smoking period.

[0070] But very advantageously, in this embodiment, two approximations ΔU10 1< MES (t) and ΔU10 2< MES (t) of the variation of the voltage U10(t) across the terminals of the heating element 10 during the smoking period are achieved, the first approximation being measured at terminals B1 and B2 of the circuit 500, the second approximation being measured at terminals B3 and B4 of the circuit 500.

[0071] This embodiment makes it possible to improve the estimation of voltage variations across the terminals of the heating element 10, regardless of the characteristics of the puff.

[0072] Indeed, thanks to the choice of time constants: The voltage measured at terminals B1 and B2 of circuit 500 is particularly representative of the voltage across the heating element R10 for a certain type of inhalation, for example a rapid and / or intense or jerky inhalation; whereas the voltage measured at terminals B3 and B4 of circuit 500 is particularly representative of the voltage across the heating element R10 for another type of inhalation, for example a slow and / or light or continuous inhalation.

[0073] In this embodiment, we then construct the following two curves ΔU10 MES (t) and ΔU10 TH (t): − Δ U 10 MES t = K 1 Δ U 10 1 MES t + K 2 Δ U 10 2 MES t − Δ U 10 TH t = K 1 Δ U 10 1 TH t + K 2 Δ U 10 2 TH t in which ΔU10 1< TH (t) and ΔU10 2< TH (t) are theoretical estimates of the approximations ΔU10 1< MES (t) and ΔU10 2< MES (t) in the absence of any inhalation during the smoking period.

[0074] We then retain, to calculate the intensity F of the inhalation, the area between these two curves ΔU10 MES and ΔU10 TH.

[0075] The coefficients K1 and K2 are fixed and determined according to the time constants of the RC circuits (the values ​​R11.C11, R12.C12 and R13.C13).

[0076] This pair of coefficients could be chosen, without limitation, according to one of the following four examples: Example 1:

[0077] K 1 = 1 / 2 ; K 2 = 1 / 2 Example 2:

[0078] K 1 = R 11 . C 11 + R 12 . C 12 / R 11 . C 11 + 2 . R 12 . C 12 + R 13 . C 13 ; K 2 = R 12 . C 12 + R 13 . C 13 / R 11 . C 11 + 2 . R 12 . C 12 + R 13 . C 13 Example 3:

[0079] K 1 = R 12 . C 12 / R 11 . C 11 / R 12 . C 12 / R 11 . C 11 + R 13 . C 13 / R 12 . C 12 K 2 = R 13 . C 13 / R 12 . C 12 / R 12 . C 12 / R 11 . C 11 + R 13 . C 13 / R 12 . C 12 Example 4:

[0080] K 1 = R 12 . C 12 − R 11 . C 11 / R 13 . C 13 − R 11 . C 11 ; K 2 = R 13 . C 13 − R 12 . C 12 / R 13 . C 13 − R 11 . C 11

[0081] To ensure proper operation, these coefficients can be tested / validated in the laboratory.

[0082] Description of an example that is not part of the invention

[0083] In the example of the figure 6, the magnitude of the voltage across the heating element that is estimated is not the variation ΔU10(t) of this voltage but the value U10(t) of this voltage itself.

[0084] In this example, we estimate this value U10(t) by measuring the voltage U5 - U10 across terminals B1 and B2 of a 500 circuit made up in this example by the measuring resistance R.

[0085] Indeed, by revisiting equation (3): U 10 t = R 10 / R . U 5 − U 10 t

[0086] This example requires connecting computing means 30 to terminals B1 and B2 of the measuring resistor R to accurately measure the variations of U5-U10.

[0087] There figure 7 represents: the approximation U10 MES (t) of the voltage U10(t) across the heating element 10 during the smoking period, calculated using equation (4), the difference of (U5 - U10)(t) being the potential difference measured by the calculation means 30 of the figure 6between points B1 and B2; the estimation of the approximation U10 TH (t) at the terminals of the heating element 10 in the absence of inhalation during said smoking period, the intensity F of the inhalation corresponding to the integration of the difference between U10 MES (t) and U10 TH (t) during the smoking period.

[0088] Description of another example which is not part of the invention

[0089] In an example shown at the figure 8 , to estimate the variation ΔU MES 10(t) of the voltage across the heating element 10, we perform, as for the first embodiment, the difference between two voltages U12(t) and U11(t) across the terminals B1 and B2 of a circuit 500, each of these voltages giving an approximation of the voltage across the heating element (10) at times slightly offset in time.

[0090] In this example, to generate this delay, we use a 500 circuit consisting of a 90 delay line between the measurement points of the voltages U11(t) and U12(t).

[0091] This line of delay could, for example, consist of: a large capacity; an analog-to-digital converter coupled to a digital-to-analog converter.

[0092] The intrinsic characteristics of the 90 delay line are not disturbed by inhalations.

[0093] Description of another example which is not part of the invention

[0094] In one example, the variation ΔU MES 10(t) of the voltage across the heating element 10 can also be estimated by calculating the time derivative of the measured voltage ΔU MES 10(t), as in the third embodiment, using the calculation means 30 of the figure 6 between points B1 and B2.

[0095] This value can be compared with the theoretical variation ΔU TH 10(t) of the voltage across the heating element 10 in the absence of inhalation, as in the first embodiment.

[0096] There figure 9 represents in the form of a flowchart a method for estimating the quantity of substrate vaporized according to an example which is not part of the invention.

[0097] This process can, for example, be implemented by the computing means 30 of the electronic cigarette of the figure 1 .

[0098] During a step E10, the computing means 30 detect the pressing of the button causing the closure of the switch 5. The instant t1 of this detection is recorded in memory.

[0099] During a step E20, just after this detection, the computing means 30 measure the voltage U0 delivered by the battery 3 and the resistivity R10(t1) of the heating element.

[0100] Every 20ms, during a step E30, until the instant t4 of detection of the release of the button causing the opening of the switch 5, the calculation means 30: They measure ΔU10 MES (t) (potential of terminal 9); they estimate ΔU10 TH (t) by reading the first database BD1 between t1 and t1+800ms. Between t1+800ms and t4, they estimate ΔU10 TH (t) = 0.

[0101] During a step E40, the computing means 30 estimate the time t2 of the start of the puff, this time being the first time after t1 such that | ΔU10 MES (t2) - ΔU10 TH (t2) | > S T2 .

[0102] During an E50 step, the computing means 30 calculate the intensity F of the inhalation as the integration of the difference between ΔU10 MES (t) and ΔU10 TH (t) between t2 and t4.

[0103] During a step E60, the computing means 30 estimate the quantity of substrate vaporized between t2 and t4 by querying the second database B2.

Claims

1. An electronic cigarette (1) comprising: a heating element (10), suitable for vaporizing a substrate, comprising a first terminal connected to ground, and a second terminal (A); a battery (3), suitable for delivering a voltage (U0); a switch (5) connected to a terminal (P) of the battery (3) and configured to supply the heating element (10) from the battery (3) only when a button is pressed; a measurement resistor (R) placed in series between a terminal (Q) of the switch (5) and the second terminal (A) of the heating element (10); computing means (30), the computing means (30) being configured to measure a voltage (U10) at the terminal (A) of the heating element (10), wherein the cigarette comprises a circuit (500) comprising an RC sub-circuit (11); wherein the RC sub-circuit (11) comprises a first resistor (R11) and a first capacitor (C11); the RC sub-circuit (11) being connected to the heating element (10) by the second terminal (A) of the heating element (10); the circuit (500) being configured to provide to the computing means (30) a voltage (U11) being an approximation of the voltage (U10) across the heating element (10) characterized in that the circuit (500) further comprises a second resistor (R12) connected to a node which connects the first resistor (R11) and the first capacitor (C11) in series, wherein the circuit (500) further comprises a second capacitor (C12) connected to ground, the second resistor (R12) and the second capacitor (C12) forming a second sub-circuit (RC12), and wherein a time constant (T12) of the second sub-circuit (RC12) is selected to be greater than a time constant (T11) of the first circuit (RC11).

2. The electronic cigarette (1) of claim 1, wherein the computing means (30) are configured to estimate a resistivity (R10(t1)) of the heating element (10) from the measured voltage (U10).

3. The electronic cigarette (1) of claim 1 or 2, comprising: a resistor (R11) comprising one terminal connected to the second terminal (A) of the heating element (10) and an opposite terminal being connected to the computing means (30) by a terminal (9).

4. The electronic cigarette (1) of claim 2 comprising: a first voltage probe (7) connected to the terminal (Q) of the switch (5); a second voltage probe (8) connected to the second terminal (A) of the heating element (10); wherein the computing means (30) are configured to estimate the resistivity (R10) of the heating element (10) from the voltage (U5) at the terminal (Q) of the switch (5) measured by the first voltage probe (7) and from the voltage (U10) at the second terminal (A) of the heating element (10) measured by the second voltage probe (8).

5. The electronic cigarette (1) of claim 1 or 2, wherein the time constant (T12) of the second RC sub-circuit (12) is greater by a factor of 100 than the time constant (T11) of the RC sub-circuit (11) comprising the first resistor (R11) and the first capacitor (C11).

6. The electronic cigarette (1) of claim 1 or 2, comprising a voltage probe (8) connected to the second terminal (A) of the heating element (10), wherein the computing means (30) are configured to measure the voltage (U10) at the second terminal (A) of the heating element (10) by means of the voltage probe (8).

7. The electronic cigarette (1) of claim 6, comprising: a first resistor (R11) connected to the heating element (10) by the second terminal in parallel, a second resistor (R12) connected to the first resistor (R11) by a node in series.