Method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop

Abstract

The present disclosure describes a method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop, comprising determining a baseline precision of the digital communication loop, generating an analog parameter value by measuring an environmental condition representative of a fire hazard with an environmental detector, converting the analog parameter value to an accurate digital parameter value with a digital precision greater than the baseline precision, splitting the digital parameter value into at least a first and a second digital parameter component, wherein each digital parameter component has a component precision of up to the baseline precision, transmitting at least a first digital signal comprising the first digital parameter component and a second digital signal comprising the second digital parameter component from the environmental detector to a central device over the digital communication loop, reconstructing the digital parameter value by the central device using the least first and second digital parameter component, and initiating a fire protection action based on an evaluation of the reconstructed digital parameter value; and a hazard protection system, environmental detector and central device therefor.

Description

Technical Field

[0001] The present invention relates generally to environmental detectors in fire protection systems and how they communicate accurate readings over a digital communication loop.Background of the Invention

[0002] Environmental detectors are commonly used in fire protection systems, playing a pivotal role in monitoring environmental conditions and providing information for analysis and assessment of fire risk situations. Environmental detectors can be installed and configured to measure an environmental condition, then locally analyze the environmental condition for risk situations, e.g. by comparing the parameter to predetermined thresholds, and then transmit the results of the analysis to a central device, a remote receiver. Alternatively, they can be installed and configured to transmit the environmental condition itself to the central device. Transmitting results of an analysis, or transmitting the measured parameter itself, poses different requirements to the characteristics of the communication protocol.

[0003] When conditions are measured and then compared to thresholds, the transmitted data of the analysis is typically limited to few signal states: e.g. one or two alarm or action states for exceeding a first or a second threshold, one state for an error or a device fault, and one idle state when no threshold is exceeded and no error occurred. For a suitable communication protocol for such detectors and central devices, only 4 possible different states would need to be transmitted. While only one state is typically transmitted at the same time, a receiver would need to be able to reliably differentiate between these states.

[0004] The measured condition can typically occupy many more states, more than 4 or similar. An environmental condition may, for example, be a continuous parameter, like temperature, and the detector may be configured to measure temperatures between -20 °C and +60 °C with a resolution of 0,5 °C. This results in 161 possible different temperature values (e.g. -20 °C, -19,5 °C, -19 °C, -18,5 °C ..., 59,5 °C, 60 °C) that may need to be transmitted. Even if a user is only interested in a reduced value range, e.g. +10 °C to +40 °C, there would still be 61 possible different values. A suitable communication protocol would thus require to handle many more different states.

[0005] In fire protection systems a known way to connect environmental detectors, and other reporters or subscribers, that require only few states to be transmitted for efficient communication, is the analogue limit value technology, often called 'conventional two-wire line'. Here, one or multiple subscribers are connected to the same two-wire line and have a variable resistance circuit inserted into one or both of the lines. Depending on the state that shall be transmitted from the detector to a central device, a different electrical resistance is applied to the two-wire line. If the central device is keeping e.g. the line voltage of the two-wire line constant, the variable resistance results in a predictable change in the current draw of the line. With a clever combination of the designated resistance values, the central device can reliably identify an alarm state from the total current draw, even if several other subscribers transmit a fault signal by applying the corresponding resistance. This protocol as is does not allow for localization of the individual subscriber that transmitted e.g. an alarm state.

[0006] An alternative way to communicate limited states between subscribers and a central device is a digital communication loop. With a digital communication loop, multiple subscribers can be connected to the loop, and are typically assigned a unique address identifier. The allowed number of subscribers on a loop depends on the digital communication loop protocol, which typically reserves a signal segment of a fixed length for the address identifier: Known protocols allow for 127 or 128, up to 1024 or even 2048 subscribers on the same loop. The subscribers need to convert the state to be transmitted locally to a digital signal. Digital communication loops known to fire protection systems often operate with signal polling, such that the central device broadcasts a polling request to all connected subscribers with an address identifier, and the addressed subscriber then responds in turn by sending a digital signal. By cycling through the subscribers and requesting information on their individual state, the central device can gather an overview of all subscribers to the digital communication loop. Any state sent back to the central device can therefore be assigned to the individual subscriber, allowing e.g. for localization of the subscriber that transmitted an alarm state. The digital communication loop may also allow for transmission of information from the central device to a subscriber.

[0007] During signal transmission, errors may occur that lead to reconstruction of a parameter at the central device that is not identical to the parameter created by the environmental detector. Known digital communication loop protocols may comprise a checksum component for the whole signal or for a segment of the signal, generated by the sender and controlled by the receiver. If a transmission error occurred in the relevant segment, the checksum component of the signal might not match a control checksum generated by the receiver. For the known digital communication loop protocols, checksum components typically are parity bits, a well-known and very simple checksum component in digital signal transmission. A parity bit is a one-bit segment typically representative of whether the total number of 1-bits (bits having the value 1) of a given segment is even or odd. Many other, longer checksum components are known and used in the field.

[0008] To allow environmental detectors to transmit a signal with a measured parameter to a central device, having many more possible states, a known analogue protocol is the 4-20 mA current loop, with a constant draw of 4 mA, often called "elevated zero", which may act as power supply to the detector, and a variable 0-16 mA to which the value range is mapped, e.g. with 0% of the value range mapped to 0 mA and 100% mapped to 16 mA, and accordingly in between. A current draw below 4 mA or above 20 mA may act as an additional state, e.g. fault. The resolution of this protocol depends on the mapping precision of the detector, and the reading precision of the central device. This protocol and its variants, is state of the art for many applications in fire protection systems, and in many other fields. This protocol as is can only receive and interpret data from a single connected detector reliably. Having e.g. two detectors on the same current loop, the total current range would be twice the individual current range, therefore 8-40 mA. The central device has no means to distinguish between a current draw of e.g. 10 mA by each detector, and 14 mA by the first plus 6 mA by the second detector, it only reads that the total current draw is 20 mA.

[0009] Alternatively, to transmit a signal with a measured parameter, some known digital communication loop protocols may allow that the segment of the digital signal which normally contains the reported limited states to be instead used for user data, open for custom configuration by the central device and the detector. The segment typically has a length of 8 bit, providing for a range of 2 8< =256 different states, which is suitable for many standard detectors to map their value range to.

[0010] With technological improvement of measuring techniques and analysis techniques, a larger value range, having e.g. 512, 1024, 2048, 4096 or even more different possible states, may need to be mapped to a digital signal for use in a digital communication loop. To accomodate, the custom signal segment and thus the whole signal could be extended to accommodate the higher number of possible states. To this end, the central device needs to be configured to interpret, and the detector itself needs to be configured to generate, the longer signal.

[0011] For standard applications, the central device would cycle through a polling queue, a predetermined list of subscribers with a predetermined order to poll a signal from an individual subscriber. If now a detector needs to transmit an extended, longer signal, the central device may adjust the time points for sending out the next polling request, or it can wait until the longer signal is completed, to avoid collision or overlap of an extended, longer signal with a standard signal.

[0012] Applicant recognized that an extended, longer signal outside of the protocol specifications, to accommodate the additional data to be transmitted using a digital communication loop may conflict with natural requirements of fire protection systems. Unlike standard applications, fire protection systems need to accommodate the demands of handling actual fire hazards in their communication protocols.

[0013] To this end, known analog protocols typically transmit their signals to the central device without significant time delay: The time which the central device requires for detecting a fire hazard, by using analog protocols as described above, mainly depends on the speed of signal generation at a subscriber and signal interpretation at the central device.

[0014] For digital communication loops, the main determining factor for responsiveness of the central device is the current position of the relevant subscriber in the polling queue. To mitigate this disadvantage, some known digital communication loop protocols allow for a subscriber which has entered an alarm state to interrupt a polling request from the central device to an addressed subscriber. To this end, a bit in the signal normally left empty by the addressed subscriber can be filled by the interrupting subscriber. This interrupt bit is preferably early in the time course to provide for the central device to react to an interrupt. Additionally, these protocols designate a signal segment at a predetermined position for the interrupting subscriber to enter its address, such that the next polling request can be directly addressed to the interrupting subscriber, to avoid any undue delay from the original position in the polling queue.

[0015] Using an extended, longer signal could shift the designated interrupt bit or the designated segment for the interrupter's address, which will consequently lead to misinterpretation or misaddressing in case of an interrupt by a subscriber that does not know or respect the extended, longer signal.

[0016] It is typical to install subscribers of different manufacturers on the same digital loop, the subscribers all being compatible with the employed standard digital communication loop protocol. Therefore, it is deemed essential for fire detection systems that the subscribers on a digital communication loop understand the protocol properties sufficiently to introduce interrupts without collision.

[0017] It is believed that there is a desire to provide a method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop to enable transmission of detector readings with a larger value range, and thus more accuracy, than currently possible without violating standardized protocol properties.Disclosure of the Invention

[0018] The presented invention solves the problem by proposing a method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of claim 1, a corresponding fire protection system of claim 11, a corresponding environmental detector of claim 12 and a corresponding central device of claim 13.

[0019] The inventive method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop comprises determining a baseline precision of the digital communication loop, generating an analog parameter value by measuring an environmental condition representative of a fire hazard with an environmental detector, converting the analog parameter value to an accurate digital parameter value with a digital precision greater than the baseline precision, splitting the digital parameter value into at least a first and a second digital parameter component, wherein each digital parameter component has a component precision of up to the baseline precision, transmitting at least a first digital signal comprising the first digital parameter component and a second digital signal comprising the second digital parameter component from the environmental detector to a central device over the digital communication loop, reconstructing the digital parameter value by the central device using the least first and second digital parameter component, and initiating a fire protection action based on an evaluation of the reconstructed digital parameter value.

[0020] The inventive method thus allows to transmit a digital parameter value of any practical length using known digital communication loops. Known digital communication loop protocols provide custom data segments of a given length per transmission signal. These custom data segments are reserved or reservable for user defined data, and the size of the reserved segments define a baseline precision of the digital communication loop, i.e. the number of different possible states available for communication via one signal according to the digital communication loop protocol. For example, a digital communication loop protocol may comprise a reserved segment of a length of 8 bit, which defines the baseline precision of that loop of 8 bit or 2 8< =256. The baseline precision thus defines the maximum precision of a reading to be transmitted via the digital communication loop.

[0021] The baseline precision is determined by the employed digital communication loop protocol. A digital communication loop protocol may comprise multiple signal types, each with an own baseline precision that may differ between the multiple signal types. In such a case, the baseline precision is determined by the selected signal type of the employed digital communication loop protocol. The signal type may be selected individually for each environmental detector.

[0022] While the baseline precision may be sufficient for readings requiring less accuracy, e.g. an ambient room temperature thermometer, it was found to be insufficient for readings requiring a higher accuracy, e.g. a high temperature range heat detector or a precise gas detector which require a precision greater than the baseline precision. To this end, according to the inventive method, the digital parameter value is split into multiple digital parameter components, extending the occupied number of custom data segments. By splitting the digital parameter value into e.g. two digital parameter components, the available bits are doubled, consequently squaring the value range. For example, a digital parameter value having a digital precision of 16 bit, or 2 16< =65.536, may be split into two digital parameter components each having a component precision of 8 bit, 2 8< =256, greatly increasing precision without losing information. The component precision is equal to or lower than the baseline precision, allowing a full digital parameter component to be transmitted by a single signal over the digital communication loop.

[0023] As the custom data segment is not exceeded, but instead occupied according to the employed protocol, the inventive method allows for full compatibility with any other subscribers compatible with said protocol, on the same loop. In other words, any other subscribers on the same digital communication loop can function and coexist, without any conflict, with environmental detectors using the inventive method. As a consequence, this method also allows to keep up with the technological progress which results in ever-increasing detection and conversion precision, while also maintaining backwards compatibility.

[0024] In can be understood that the digital precision represents the desired accuracy, the baseline precision represents the technical limitations, and the component precision represents the means to circumvent the technical limitations and to achieve the desired accuracy.

[0025] It is understood, that the at least first and second digital signals are the digital signals generated and transmitted by a subscriber, specifically an environmental detector. The at least first and second digital signals can preferably be generated by attaching the components generated at different sources to each other. For example, a signal could start with a leading sequence to indicate the start of the signal, followed by the digital parameter value, followed by an identification segment. Depending on how the order of reports from the subscribers is managed, the digital signals may not need a leading sequence or an identification segment. On the other hand, the digital signal may also comprise many digital components in addition to the components disclosed in detail in this application. Typical other components comprise time stamps, device information, software revision information, confirmation of control inputs, and others. It is further understood, that a subscriber may also simply append its own signal components to a signal part from other subscribers or from the central device. For example, a central device may broadcast a segment, naturally to all subscribers, which in turn triggers subscribers to append their digital parameter value, either in a predetermined order or in response to an additional stimuli. It is important to note that the process of generating a signal may precede the transmission of said signal, or it may take place simultaneously such that the digital signal is never fully assembled before the bits of the signal are modulated on the digital communication loop.

[0026] Reconstructing the digital parameter value by the central device using the least first and second digital parameter component requires the individual components to be stored in a memory accessible by the central device, as the individual components are transmitted at different times and not necessarily one after the other. The digital parameter value may be reconstructed in the reverse manner in which they were split, by attaching one component to the next in strict order.

[0027] The central device is configured to initiate a fire protection action based on an evaluation of the reconstructed digital parameter value. Conventional detectors typically have implemented a comparison logic to locally evaluate the measured data and compare that data to action thresholds and then transmit only few states including an alarm or action state, on which the central device can directly act. Environmental detectors configured to transmit a digital representation of an environmental condition instead require a central device capable of advanced signal evaluation to identify risk situations from a stream of accurately measured data. While known central devices, like fire detection panels, can be configured to evaluate an analog 4-20 mA signal and act based on that 4-20 mA signal, the central devices of this preferred embodiment need to be able to evaluate, and typically also store, digital signals representative of environmental condition. Evaluation of signals may comprise determination of absolute values and averages of such absolute values, determination of temporally dynamic trends and shifts, comparison of said determined parameters against alarm or action criteria. For example, the digital parameter value may be compared against a first fire hazard threshold. More specifically, an oxygen gas concentration in a room protected by an oxygen reduction system may be evaluated and compared against a first, lower and a second, slightly higher threshold. When the measured oxygen concentration exceeds the first threshold, performance of an oxygen extraction system may be increased, or inert gas may be injected into the room.

[0028] Fire protection actions may include emergency control of doors, elevators, machines, or other security features connected to the fire protection system. Preferably, fire protection actions include a fire extinguishing action, like remote controlled activation of a water, foam or gas extinguishing system, and / or a fire prevention action, like reducing amount and / or concentration of combustible gases or oxygen in a risk area, e.g. by flooding the area with inert gases, to prevent the beginning or the spreading of a fire. Initiation of fire protection actions by the central device are time critical actions that benefit strongly from enabling interrupts without signal collision.

[0029] A preferred central device is configured to generate an alarm based on an evaluation of the reconstructed digital parameter value. When fire protection actions of the inventive method are insufficient to mitigate the fire risks, an alarm signal is be generated, informing persons in the room or in other locations, or a remote central fire panel. Specifically, the alarm may be generated if the fire hazard risk is not mitigated within a specified time window. Alternatively or in addition, the alarm may be generated if a second fire hazard threshold of the digital parameter value is exceeded.

[0030] In a preferred embodiment, the digital communication loop is a two-wire loop and the environmental detector is configured to be fully operated by the two-wire loop. Some known environmental detectors for which it would be advantageous to transmit larger value ranges are type-specific gas detectors, like oxygen gas detectors. A large part of commonly installed type-specific gas detectors in the fire protection field require power-demanding heating of the gas sensing elements, e.g. the electrochemical cell. For example, an oxygen gas detector may operate on only 4 mA for sensing and communication, but may require 500 mA for permanent heating of the sensing element. Such current draw typically exceeds the provided baseline power of common two-wire communication protocols, both analog and digital, resulting in a demand for a third wire to provide the additional heating power. As the heating power may need to be individually controlled by a remote device, typically the central device that is also to receive communication from the detectors, additional installation effort is required to provide the third wire from the detector directly to the central device. In such a situation, if direct wiring is required nonetheless, the advantages of the inventive method diminished such that a single subscriber protocol like an analog 4-20 mA protocol may be preferred. On the other hand, the advantages of the inventive method can take full effect when used with an environmental detector which does not require a third, direct cabling to a remote device, leading to minimal installation and operating effort.

[0031] Preferably, the environmental condition is a continuous physical property of the environment, more preferably temperature or concentration of a gas. Some environmental conditions, like positioning of valves or other objects, states of lighting, number of critical objects identified in a video feed, activation frequency of movement detectors, are discreet in nature and the number of transmittable different states is limited. Such discreet environmental conditions would typically not exceed the number of different states allowed in a single signal transmission. On the other hand, continuous environmental conditions theoretically can have unlimited different states. Even more so, the number of different states does not depend on imaginable, but yet unimagined states of a discreet parameter to monitor. Instead, technological advancement of analog-to-digital and digital-to-analog converter naturally and predictably leads to a respective increase in precision and consequently number of different states for a given absolute range. For example, temperature sensors are known in the field that convert the analog parameter value to a digital parameter value and then transmit that digital parameter value using a digital communication loop after converting. The analog to digital conversion precision of these known temperature sensors is so low that, on one hand, it allows digital communication with single signals instead of using the inventive method as proposed in this application. But on the other hand, it allows only for superficial and range-limited temperature determination and not for reliable drift detection, temperature dynamics detection or high temperature range detection, e.g. detecting temperatures between 0 °C and +400 °C with a resolution of 1 °C.

[0032] In another preferred embodiment, at least one of the at least first and second digital signals comprises a checksum component, preferably a parity check, generated by the environmental detector from the at least first and second digital parameter components and / or the digital parameter value, and the central device is configured to determine data integrity of the digital parameter value using the checksum component. For the inventive method, the known use of checksum components for one signal or a segment of one signal is insufficient to reliably detect transmission errors. For example, if the whole second digital signal is lost in transmission and needs to be resent by the environmental detector, the first digital signal may be resent mistakenly. Here, the falsely reconstructed digital parameter value then would comprise two first digital parameter components, resulting in a digital parameter value very far from the measured parameter value. The conventional checksum component, as it is generated only from the individual signal, would not indicate the transmission mistake of this example. A checksum component generated from several, e.g. pairwise, or all digital parameter components at once, or even generated from the original digital parameter value as a whole, would instead indicate the transmission mistake, especially a lost signal, which would have compromised integrity of the digital parameter value as received by the central device. A checksum component may be part of the custom segment within which the digital parameter components are transmitted according to the inventive method. If a checksum component is to be included in a custom segment in addition to a digital parameter component, the component precision is consequently limited to avoid violation of used protocol specifications. Preferably, the checksum component is transmitted in each of the digital signals which transmit the digital parameter components.

[0033] For example, a 16 bit digital parameter value may be split into two components and transmitted in an 8 bit custom segment via two digital signals without a checksum component. The 16 bit digital parameter value may also be split into three components of e.g. 6, 6 and 4 bit length, leaving 2 bit in each 8 bit segment for an extended checksum component. The digital parameter value may be split up into even more digital parameter components, consequently reducing component precision, to allow the extended checksum component to be more complex and more reliable, but also occupying more bits. For example, a 16 bit digital parameter value may be split into four components of 4 bit each, allow for a 4 bit checksum component. Preferably, the checksum component represents a parity check with a length of 1 bit.

[0034] In a preferred embodiment, the central device is configured to uniquely identify the environmental detector using at least a first and a second digital address component. Using digital address components to identify subscribers, i.e. assigning a unique address to them, instead of e.g. identification by position in an unmodified queue, allows communication over the digital communication loop to directly address a subscriber outside of a typically predetermined queue. This also enables modification of the order in which subscribers transmit their respective signal or signals during operation. For example, an interrupt function may be implemented in the digital communication loop protocol such that an interruption segment is reserved for an interrupting subscriber to place a short, e.g. 1 bit, signal in that interruption segment, and an interruption address segment is reserved for the interrupting subscriber to place its digital address component in that interruption address segment.

[0035] In a more preferred embodiment, the at least first and second digital signals comprise the at least first and second digital address components. This allows the central device to uniquely identify a subscriber by the signal sent by said subscriber. If the central device expects a certain subscriber to transmit its signal or its signals, having the digital address components as part of the signals allows for confirmation of the correct subscriber.

[0036] Alternatively or in addition, the at least first and second digital signals are transmitted in response to at least a first and a second polling request received by the environmental detector from the central device. The central device typically has a stored queue in which it expects the subscribers to transmit their signal or signals. To reduce likeliness of receiving a wrong signal, or a signal at a wrong time, the central device may be configured to broadcast polling requests, leading in turn to transmission of the respective signals. The signals may still transmitted according to a queue, but are less likely to collide when transmission is only initiated upon polling request. Preferably, the at least first and second polling request comprise the at least first and second digital address components. When polling requests each comprise a respective digital address component, the subscribers do not need to store, maintain and / or synchronize the queue any longer. Instead, they can operate completely in response to the polling request.

[0037] More preferred, the digital parameter value is split into the at least first and second digital parameter component in response to the first or to the at least first and second polling request from the central device. Typically, an environmental detector generates the analog parameter value by measuring the environmental condition with a much higher frequency than it is configured to transmit the corresponding digital parameter value. When the time between individual transmissions of digital parameter value exceeds the time between individual measurements of the environmental condition by several times, it may be preferable to not generate the corresponding at least first and second digital signals to avoid unnecessary processing load, and thus electrical component strain and power consumption. Instead, it may be preferred to execute only a subset of method steps. For example, the environmental detector may be configured to generate the analog parameter value at its measuring frequency, but to convert the latest analog parameter value to a digital parameter value at a frequency less than, e.g. at 10 % of, the measuring frequency. This means that the e.g. 9 out of 10 analog parameter values are discarded, or at least not converted into a digital parameter value. The detector may be configured to either extract all digital parameter components in a single process, preferably in response to the first polling request, after which it may discard the digital parameter value, or it may be configured to maintain the digital parameter value and extract the digital parameter components only one at time, preferably in response to each polling request individually. The converted digital parameter values may preferably be stored, more preferably in a circular buffer, i.e. a data memory that stores a finite amount of data and continuously overwrites the oldest entry with a newest entry. The detector may be configured to split the latest digital parameter value into the at least first and second digital parameter components only in response to the first polling request. The detector may be configured to then generate the at least first and second digital signals, and store them until the respective individual signal, e.g. the second, is polled specifically. Alternatively, the individual digital signal may be generated only when polled, and the required respective digital parameter components may be retrieved from an internal memory.

[0038] More alternatively, the analog parameter value is converted to the digital parameter value in response to the first polling request from the central device. Here, the detector may be configured to generate the analog parameter value at its measuring frequency, but without converting it into the digital parameter value unless explicitly requested. Upon receiving the first polling request, the environmental detector may either convert the last analog parameter value when said value is still available, e.g. by being stored in a memory, or it converts the next or a later analog parameter value. The detector would then continue to split the digital parameter value, generate and then transmit the signals.

[0039] Preferably, the at least first and second address components are each non-identical, i.e. the environmental detector has multiple unique addresses, at least one for each digital signal required to transmit the digital parameter components required for reconstruction of the digital parameter value. Transmitting each digital parameter component in combination with a non-identical unique address component allows for the central device to reconstruct the digital parameter value simply by knowing the order of unique addresses according to which the digital parameter components were created by splitting the digital parameter value. The environmental detector is preferably configured to react to a list or an unspecified range of non-identical addresses using the same physical communication means, e.g. a single communication module configured to communicate over the digital communication loop. Alternatively it may comprise multiple physical communication means, each assigned to react a singular unique address.

[0040] Alternatively, the at least first and second address components are each identical, i.e. the environmental detector has a single address, and thus each digital signal from that environmental detector comprises an identical address component. In this embodiment, the identification of the actual digital parameter component, i.e. which of the multiple components is requested and received via a given signal, needs to be achieved by other means. For example, some known digital communication loop protocols provide for a layer indicator which uniquely identifies one specific layer of several layers of the custom segment. The layer indicator is an additional layer address datum to specify which exact layer is requested and / or transmitted in the given digital signal. This allows that over multiple digital signals transmitted by a single environmental detector, the multiple digital parameter components can be individually requested, and identified by the central device.

[0041] A preferred fire protection system comprises a central device, multiple fire protection units, or subscribers, including at least one environmental detector configured to measure an environmental condition representative of a fire hazard, the multiple fire protection units being connected to the central device by a digital communication loop having a baseline precision, wherein the at least one environmental detector and the central device of the preferred fire protection system are configured to use any of the disclosed inventive methods of this application.

[0042] A preferred environmental detector arrangement for a fire protection system comprises a measuring module, a communication module configured to communicate with a central device using a digital communication loop having a baseline precision, and a processing module, the environmental detector arrangement being configured to generate an analog parameter value by measuring an environmental condition representative of a fire hazard using the measuring module, convert the analog parameter value to an accurate digital parameter value with a digital precision greater than the baseline precision, split the digital parameter value into at least a first and a second digital parameter component, wherein each digital parameter component has a component precision of up to the baseline precision, generate at least a first digital signal comprising the first digital parameter component, and a second digital signal comprising the second digital parameter component, and transmit the at least first and second digital signals from the environmental detector to the central device over the digital communication loop using the communication module.

[0043] The preferred environmental detector is preferably configured to use any steps of the disclosed inventive methods of this application that are attributed and / or applicable to the environmental detector. A measuring module is configured to measure the environmental condition and can be for example a temperature dependent resistance, a gas-specific resistance, an electrochemical cell, a photo-sensitive diode, or any other measuring or sensing components known in the field. All variants can be circuit-assisted, having electrical circuits enhancing or controlling their function. The processing module can be a central processor unit (CPU), a microprocessor or an integrated circuit (IC) and may be configured to assist the measuring module in generating the analog parameter value. It may also be configured to convert the analog parameter value to the digital parameter value, and even to split the digital parameter value, and to this end can comprise an analog-to-digital converter. A communication module can be a one-way, from detector to central device, or a two-way communication device, which is at least able to manipulate and introduce signals onto the digital communication loop. The communication module can be integrated into the general circuitry of the environmental detector, or it may be an attachable module in signal connection with the general circuitry. The communication module may also be a component outside of the housing of the environmental detector and in signal communication with it. The communication module may also be configured to provide the capabilities to convert analog signals into digital signals. Signal communication may then be established using other communication protocols, for example the analog 4-20 mA protocol described earlier. This would allow the method to be used with environmental detectors not compatible on their own with digital communication loops, or the specific digital communication loops.

[0044] A preferred central device, preferably a fire detection panel, comprises a central communication module configured to communicate with a fire protection unit, including an environmental detector configured to measure an environmental condition, using a digital communication loop having a baseline precision, and a central processing module, with the central device being configured to receive from the environmental detector at least a first digital signal comprising a first digital parameter component and a second digital signal comprising a second digital parameter component, wherein each digital parameter component has a component precision of up to the baseline precision, and reconstruct a digital parameter value with a digital precision greater than the baseline precision using the least first and second digital parameter component, the digital parameter value being representative of the environmental condition measured by the environmental detector.

[0045] The preferred central device is preferably configured to use any steps of the disclosed inventive methods of this application that are attributed and / or applicable to the central device. A central communication module can be integrated into the general circuitry of the central device, or it may be an attachable module in signal connection with the general circuitry. In modern fire panels, communication functions are typically encapsulated in removable modules, to allow custom assembly of the panel functions with the required communication channels. A central processing module of the central device can be a central processor unit (CPU), a microprocessor or an integrated circuit (IC). Central processing modules may analyze complex signals, coordinate various communication channels in parallel, generate alarm signals, control fire protection actions, among others. Modern fire panels typically comprise one or even more high functioning main-CPUs to perform required analysis, although execution of specific functions can also be localized to processing components of non-central extensions, like communication modules. For example, reconstruction of the digital parameter value may take place in the communication module itself.Description of the Drawings

[0046] The accompanying drawing, which is incorporated herein and constitutes part of this specification, illustrates exemplary embodiments of the invention, and together, with the general description given above and the detailed description given below, serves to explain the features of the invention. It should be understood that the preferred embodiments are some examples as provided by the appended claims. Fig. 1is a schematic flowchart of a preferred embodiment of the inventive method. Fig. 2is another flowchart of a part of a preferred embodiment of the inventive method.

[0047] Fig. 1 shows a method of operating an environmental detector in a hazard protection system according to a preferred embodiment of the invention.

[0048] In a first step, the baseline precision (PB) of the digital communication loop (5) is determined. The baseline precision (PB) in this embodiment could be 8 bit, i.e. 256 different possible states over a given value range.

[0049] In a further step (101), the environmental detector generates an analog parameter value by measuring an environmental condition. The environmental condition could be temperature, radiation intensity or concentration of a compound in an ambient environment, e.g. a specific gas in an atmosphere or a chemical in a fluid, perceived by the environmental detector. The analog parameter value (V) is a representation of the environmental conditionin the form of an analog electrical signal, e.g. a current or a voltage.

[0050] In a next step (102), the analog parameter value (V) is converted into a digital parameter value (D), in this embodiment by an electronic analog-to-digital (A-to-D or A / D) converter. The A / D converter maps a continuous analog electrical signal to a discreet digital signal. It is characterized by the lower and upper boundary of the analog input signal, defining the relevant analog value range of the input signal, and its resolution, i.e. the amount of different discreet (digital) states it can map the relevant analog value range of the analog input signal to. The A / D converter provides one connector per bit to pick off each individual bit value.

[0051] The step (102) of this method variant, of converting the analog parameter value (V) into a digital parameter value (D), is initiated in response to receiving (111) a first polling request (P1) from the central device. Without a polling request, the generated analog parameter values (V) are discarded.

[0052] Alternatively (dashed arrow), the receiving (111) of a first polling request (P1) may instead initiate splitting of the digital parameter value (D) is split into a first (S1) and a second (S2) digital parameter component (step 103a,b).

[0053] Alternatively (dotted arrow), the receiving (111) of a first polling request (P1) may instead initiate transmitting of the first (S1) and second (S2) digital signals (step 104a,b).

[0054] In a further step (103a,b), the digital parameter value (D) is split into a first (S1) and a second (S2) digital parameter component. The bits of each digital parameter component are extracted directly from the output connectors of the A / D converter.

[0055] In a next step (104a,b), the first (S1) digital signal comprising the first digital parameter component (D1) of step 103a is transmitted (104a) to the central device (10), and the second (S2) digital signal comprising the second digital parameter component (D2) of step 103b is also transmitted (104b) to the central device (10). Transmission of these signals is not simultaneous, as the loop typically can only transmit one subscriber signal after the other.

[0056] After transmission of the digital signals (S1,S2) to the central device (10) in step 104a,b, the digital parameter value (D) is reconstructed (105) in the central device (10), from the first (D1) and second (D2) digital parameter components. From here on, the digital parameter value (D) may be further analyzed, stored or communicated to another distant receiver.

[0057] The reconstructed digital parameter value (D) is evaluated (110) by comparison against predetermined or dynamically adjusted thresholds, and based on that evaluation, a hazard protection action or an alarm action may be initiated by the central device (10).

[0058] Fig. 2 shows a less abstract flowchart of a part of a preferred embodiment of the invention, specifically of the parameter value and the digital signals.

[0059] The continuous environmental condition, oxygen concentration [Oz], is measured over time by an environmental detector, generating a time series of analog parameter values. An individual analog parameter value (V) is extracted from the measurement for a given data point of the time series.

[0060] This analog parameter value (V) is converted into a digital parameter value (D) having a digital precision (PD) of 16 bit, depicted by 16 squares to be filled with high or low, resp. 1 or 0. The digital parameter value (D) thus comprises 2 16< =65.536 possible different states which are spread over the predetermined value range. For example, if the analog-to-digital converter has a lower bound of 0 mA corresponding to 0 % [Oz] and an upper bound of 30 mA corresponding to 30 % [Oz], the value range of 30 mA is mapped to the 65.536 states, resulting in the smallest increment between two values ("least significant bit", LSB), of 30 mA / 65.536 = 0,46 µA.

[0061] In another example using state of the art methods and protocols, the analog parameter value (V) would need to be converted into a digital parameter value (D) having a digital precision (PD) of only up to the baseline precision (PB) of 8 bit for known digital communication protocols. Using an analog-to-digital converter with a lower bound of 0 mA corresponding to 0 % [Oz] and an upper bound of 30 mA corresponding to 30 % [Oz], the value range of 30 mA is then mapped to only 2 8< =256 states, resulting in a least significant bit (LSB) of 30 mA / 256 = 0,12 mA.

[0062] In these examples, the inventive method has a resolution of the transmittable parameter value which is 0,12 mA / 0,46 µA = 256 times greater than the known method.

[0063] The digital parameter value (D) with its digital precision (PD) of 16 bit is split into a first digital parameter component (D1) having a component precision (PD) of 8 bit, which comprises the left half, or bits 8 to 15, of the digital parameter value (D), and a second digital parameter component (D2) having a component precision (PD) of 8 bit, which comprises the right half, or bits 0 to 7, of the digital parameter value (D). Within this application, bits are counted from right to left and the first bit of any digital component is the rightmost bit and referred to as "bit 0".

[0064] In response to predetermined criteria (not shown), the first digital signal (S1) and the second digital signal (S2) are individually generated and transmitted over a digital communication loop (5, not shown) having a baseline precision of at least 8 bit, thus allowing one digital parameter component with a component precision of 8 bit to be transmitted per signal. Each digital signal (S1,S2) contains its respective digital parameter component (D1,D2) and, respectively, a first (A1) and a second (A2) 7 bit digital address component. The 7 bit digital address components (A1,A2) comprises a digital address allow a receiving central device (10, not shown) to identify or to confirm identification of the sender of the respective digital signal (D1 ,D2). A 7 bit digital address component allows for up to 128 different address and thus for up to 128 different devices to be uniquely addressed. It may be required to assign multiple different addresses to one device, for example an environmental detector requiring an individual address for each digital parameter component, which would in turn reduce the maximum amount of uniquely addressed device accordingly.

[0065] The first (S1) and second (S2) digital signals are received by the central device and identified by the respective digital address components (A1,A2). The central device extracts and stores the first digital parameter component (D1) with a component precision of 8 bit from the first digital signal (S1) upon receipt and the second digital parameter component (D2) with a component precision of 8 bit from the second digital signal (S2) upon receipt.

[0066] The stored first (D1) and second (D2) digital parameter components each with a component precision of 8 bit are reassembled into the original digital parameter value (D) with a digital precision (PD) of 16 bit, by inserting the first 8 bit digital parameter component (D1) as the left half, or bits 8 to 15, and the second 8 bit digital parameter component (D2) as the right half, or bits 0 to 7, of the digital parameter value (D).

[0067] The digital parameter value (D) is now fully assembled and can be stored, evaluated, further transmitted, or processed in any other manner.List of References

[0068] 1a,bEnvironmental detector 2a,bFire protection unit 5Digital communication loop 10Central device 100Determination of baseline precision 101Generation of analog parameter value 102Conversion into digital parameter value 103a,bSplitting into digital parameter components 104a,bTransmission of digital signals 105Reconstruction of digital parameter value 110Evaluation of digital parameter value 111Reception of polling request PBBaseline precision VAnalog parameter value DDigital parameter value PDDigital precision D1,D2Digital parameter components PCComponent precision S1,S2Digital signals CSChecksum component A1,A2Digital address components P1,P2Polling requests

Claims

1. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop, the method comprising - Determining a baseline precision (PB) of the digital communication loop (5), - Generating an analog parameter value (V) by measuring an environmental condition representative of a fire hazard with the environmental detector (1), - Converting the analog parameter value (V) to an accurate digital parameter value (D) with a digital precision (PD) greater than the baseline precision (PB), - Splitting the digital parameter value (D) into at least a first (D1) and a second (D2) digital parameter component, wherein each digital parameter component (D1,D2) has a component precision (PC) of up to the baseline precision (PB), - Transmitting at least a first digital signal (S1) comprising the first digital parameter component (D1) and a second digital signal (S2) comprising the second digital parameter component (D2), from the environmental detector (1) to a central device (10) over the digital communication loop (5), - Reconstructing the digital parameter value (D) by the central device (10) using the least first (D1) and second (D2) digital parameter component, - Initiation of a fire protection action based on an evaluation of the reconstructed digital parameter value (D).

2. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of claim 1, characterized in that the central device (10) is configured to generate an alarm based on the reconstructed digital parameter value (D).

3. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of claims 1 or 2, characterized in that the digital communication loop (5) is a two-wire loop, and the environmental detector (1) is configured to be fully operated by the two-wire loop.

4. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of any of claims 1 to 3, characterized in that the environmental condition is a continuous physical property of the environment, preferably temperature or concentration of a gas.

5. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of any of claims 1 to 4, characterized in that the method further comprises the steps - Generating a checksum component (CS), preferably a parity check, from the at least first (D1) and second (D2) digital parameter components and / or the digital parameter value (D) by the environmental detector (1), - Transmitting the checksum component (CS) as part of the at least first (S1) and second (S2) digital signals, and - Determining data integrity of the digital parameter value (D) using the checksum component (CS) by the central device (10).

6. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of any of claims 1 to 5, characterized in that the central device (10) is configured to uniquely identify the environmental detector (1) using at least a first (A1) and a second (A2) digital address component.

7. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of claim 6, characterized in that the at least first (S1) and second (S2) digital signals comprise the at least first (A1) and second (A2) digital address components.

8. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of claims 6 or 7, characterized in that the at least first (S1) and second (S2) digital signals are transmitted in response to at least a first (P1) and a second (P2) polling request received by the environmental detector (1) from the central device (10), and the at least first (P1) and second (P2) polling requests comprise the at least first (A1) and second (A2) digital address components.

9. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of any of claims 6 to 8, characterized in that the at least first (A1) and second (A2) address components are each identical.

10. A method of communicating an accurate reading of an environmental detector in a fire protection system over a digital communication loop of any of claims 6 to 8, characterized in that the at least first (A1) and second (A2) address components are each non-identical.

11. A fire protection system, comprising - A central device (10), - Multiple fire protection units (2), including at least one environmental detector (1) configured to measure an environmental condition representative of a fire hazard, connected to the central device (10) by a digital communication loop (5) having a baseline precision (PB), characterized in that the at least one environmental detector (1) and the central device (10) are configured to execute the method of any of claims 1 to 9.

12. An environmental detector (1) arrangement for a fire protection system, comprising - A measuring module, - A communication module configured to communicate with a central device (10) using a digital communication loop (5) having a baseline precision (PB), and - A processing module, The environmental detector (1) being configured to - Generate an analog parameter value (V) by measuring an environmental condition representative of a fire hazard, - Convert the analog parameter value (V) to an accurate digital parameter value (D) with a digital precision (PD) greater than the baseline precision (PB), - Split the digital parameter value (D) into at least a first (D1) and a second (D2) digital parameter component, wherein each digital parameter component (D1,D2) has a component precision (PC) of up to the baseline precision (PB), - Transmit at least a first digital signal (S1) comprising the first digital parameter component (D1) and second digital signal (S2) comprising the second digital parameter component (D2) to the central device (10) over the digital communication loop (5).

13. A central device (10), comprising - A central communication module configured to communicate with a fire protection unit (2), including an environmental detector (1) configured to measure an environmental condition, using a digital communication loop (5) having a baseline precision (PB), and - A central processing module, the central device (10) being configured to - Receive from the environmental detector (1) at least a first digital signal (S1) comprising a first digital parameter component (D1) and a second digital signal (S2) comprising a second digital parameter component (D2), wherein each digital parameter component (D1,D2) has a component precision (PC) of up to the baseline precision (PB), and - Reconstruct a digital parameter value (D) with a digital precision (PD) greater than the baseline precision (PB), using the least first (D1) and second (D2) digital parameter component, the digital parameter value (D) being representative of the environmental condition measured by the environmental detector (1).

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