Gas measuring device and gas measuring method for a target gas with improved compensation of an ambient condition

Abstract

The invention relates to a gas measuring device (100) and a gas measuring method capable of measuring the concentration of a target gas. A detector detection variable sensor (12.1) measures a measure of a detection variable (U10) of a detector, wherein this detector detection variable (U10) correlates with the concentration of the target gas in a gas sample (Gp). A compensator detection variable sensor (12.2) measures a measure of a detection variable (U11) of a compensator, wherein this compensator detection variable (U11) correlates less with the target gas concentration. The gas measuring device (100) can be operated in a pressure-compensating mode and / or in a humidity-compensating mode. In pressure-compensating mode, the influence of ambient pressure on a measurement result is compensated as best as possible under the boundary condition that the influence of ambient humidity remains sufficiently small.In the humidity compensating mode, the influence of ambient humidity on a measurement result is compensated as best as possible under appropriate boundary conditions.

Description

[0001] The invention relates to a gas measuring device and a gas measuring method which are capable of measuring the concentration of a target gas and can be operated in different modes, wherein in each mode the influence of a non-directly measured ambient condition on a detection variable is well compensated and wherein it depends on the mode which ambient condition is compensated.

[0002] In a preferred embodiment, the invention applies a principle known from the prior art, also known as a "catalytic catalytic sensor." In this embodiment, the target gas is combustible, meaning it can be oxidized. A detector heats a gas sample in a measuring chamber. The heating of the detector leads to oxidation of the combustible target gas. The oxidation releases heat energy. The released heat energy further heats the detector, and a detector detection variable that correlates with the detector temperature is measured. The further heating and thus the detector detection variable correlate with the desired concentration of combustible target gas.

[0003] Further heating of the detector depends not only on the target gas concentration but also on ambient conditions. It is also known from the prior art to use a compensator that oxidizes less or no target gas at all, but ideally reacts to ambient conditions in the same way as the detector. A detection variable of the compensator is measured and used to compensate for the influence of ambient conditions on the detector's detection variable.

[0004] The invention can also be applied to a gas measuring device that uses a different principle to measure the concentration of a target gas, in particular an optical measuring method with a radiation source and a photodetector or an acoustic measuring method with a radiation source or sound source and an acoustic sensor.

[0005] The invention is based on the object of providing a gas measuring device and a gas measuring method which are capable of measuring the concentration of a target gas and of compensating the influence of an ambient condition on the measurement better than known gas measuring devices and gas measuring methods.

[0006] The object is achieved by a gas measuring device having the features of claim 1 and by a gas measuring method having the features of claim 12. Advantageous embodiments of the gas measuring device according to the invention are, to the extent appropriate, also advantageous embodiments of the gas measuring method according to the invention and vice versa.

[0007] The gas measuring device according to the invention is capable of measuring the concentration of at least one target gas in a spatial area. In one application, the target gas is a flammable target gas; in another application, it is another target gas harmful to humans. The target gas can also be a gas essential to human life, such as oxygen, carbon dioxide, or an anesthetic. Typically, the gas measuring device only provides an estimated value (approximate value) for the actual target gas concentration. The gas measuring method according to the invention is carried out using a gas measuring device according to the invention.

[0008] A gas sample flows from the area to be monitored into the interior of the gas measuring device and reaches both a detector and a compensator of the gas measuring device.

[0009] The detector has a measurable detector detection quantity, e.g., electrical voltage or current. This detector detection quantity correlates with the concentration of the target gas in a gas sample. A detector detection quantity sensor of the gas measuring device can measure a measure of the detector detection quantity.

[0010] The compensator has a measurable compensator detection quantity. The compensator detection quantity correlates less than the detector detection quantity, or even not at all, with the target gas concentration. A compensator detection quantity sensor of the gas measuring device is capable of measuring a measure of the compensator detection quantity. It is possible that a detection quantity sensor is capable of measuring an overall detection quantity that depends on both the detector detection quantity and the compensator detection quantity.

[0011] The gas sample originates from a spatial area to be monitored. Environmental conditions, particularly the ambient temperature, in this spatial area affect the gas sample. As a rule, the detector detection variable is therefore inevitably influenced by at least one environmental condition, particularly the ambient temperature. The compensator detection variable is also influenced by this environmental condition. However, the compensator detection variable correlates less with the target gas concentration than the detector detection variable and, in one embodiment, does not depend on the target gas concentration at all. Ideally, both detection variables depend equally on all environmental conditions. In practice, this ideal situation is generally unattainable.

[0012] A signal-processing evaluation unit can automatically determine the concentration of the target gas in the gas sample. For this determination, the evaluation unit uses the measured detector detection quantity (i.e., a signal from the detector detection quantity sensor), the measured compensator detection quantity (i.e., a signal from the compensator detection quantity sensor), and optionally a signal from an ambient condition sensor. It is possible for the evaluation unit to use the respective signal from at least two ambient condition sensors.

[0013] The determined target gas concentration therefore depends on both the detector detection variable and the compensator detection variable. The compensator detection variable allows for computational compensation, to a certain extent, for the influence of the ambient temperature and the influence of at least one other environmental condition on the detector detection variable.

[0014] In a preferred implementation, a total detection variable is calculated by applying a functional relationship, which preferably comprises a weighted average of the detector detection variable and the compensator detection variable. The target gas concentration is determined as a function of the total detection variable. In pressure-compensated mode, this functional relationship depends differently on the detector detection variable and / or the compensator detection variable than in humidity-compensated mode. For example, the weighting factor with which the detector detection variable is incorporated into the functional relationship and / or the weighting factor of the compensator detection variable differ from mode to mode.

[0015] As a rule, the gas measuring device according to the invention does not provide the actual target gas concentration as the measurement result, but rather an estimated value for the target gas concentration. In the following, the "measurement result of the gas measuring device" or the "determined target gas concentration" is referred to, whereby the determined target gas concentration generally deviates from the actual target gas concentration. The determined target gas concentration should deviate relatively little from the actual target gas concentration. How this is achieved according to the invention is described below.

[0016] The detector detection variable and thus the signal of the detector detection variable sensor depend on the one hand on the desired target gas concentration and on the other hand on three environmental conditions: the ambient temperature, the ambient humidity, and the ambient pressure. The gas measuring device according to the invention can comprise a sensor for one environmental condition. The invention demonstrates a way to take the respective influence of these three environmental conditions into account without the gas measuring device necessarily having to have a sensor for each environmental condition.

[0017] The gas detection device can be operated in at least one of at least two different modes. One of these modes is a pressure-compensated mode, and the other of these modes is a humidity-compensated mode. During a single use, the gas detection device operates in one mode. It is possible for it to operate in two different modes during two consecutive uses.

[0018] In pressure compensating mode, the influence of ambient pressure on the measurement result is compensated as follows: - The boundary condition is met that the influence of ambient humidity on the measurement result remains below a specified upper humidity influence limit. In other words: For any ambient humidity value that may occur during use of the gas measuring device, the measured value deviates from the actual target gas concentration by a maximum of the upper humidity influence limit. This upper limit is specified, for example, in % LEL (lower explosion limit). - The influence of the ambient pressure on the measurement result of the gas measuring device is compensated as best as possible, while observing the boundary condition just mentioned.

[0019] Accordingly, in the humidity compensating mode, the influence of ambient humidity on the measurement result is compensated as follows: - The boundary condition is met that the influence of the ambient pressure on the measurement result remains below a specified upper pressure influence limit. - The influence of ambient humidity on a measurement result is compensated as best as possible by observing this boundary condition.

[0020] In pressure-compensated mode, the determined target gas concentration depends in a first way on the detector detection variable and the compensator detection variable, and in humidity-compensated mode, in a second way. These two modes differ from each other. For example, the determined target gas concentration depends on a weighted average of the two detection variables, with at least one weighting factor being different for one mode than the other.

[0021] According to the invention, the gas measuring device can be operated in at least one of at least two different modes. In one embodiment, it can be operated in at least one of four different modes, namely additionally in a pressure-optimized and / or a humidity-optimized mode. In the pressure-optimized mode, the influence of the ambient pressure on a measurement result of the gas measuring device is compensated for as best as possible, i.e., without adhering to a boundary condition relating to a different ambient condition. Accordingly, in the humidity-optimized mode, the influence of the ambient humidity on the measurement result is compensated for as best as possible, i.e., without adhering to a boundary condition relating to a different ambient condition.

[0022] The at least two different modes make it possible to adapt the gas measuring device to specific operating conditions and to specific requirements regarding the accuracy of the measurement result. For example, it is expected that the ambient pressure will fluctuate significantly during an application, while the ambient humidity remains approximately constant. This operating condition occurs, for example, when the target gas concentration is measured in a pipe with a gas mixture flowing through the pipe. In this case, the gas measuring device is preferably operated in pressure-compensated or even in the optional pressure-optimized mode. If, on the other hand, it is expected that the ambient humidity will fluctuate significantly while the ambient pressure remains approximately constant, the gas measuring device is preferably operated in humidity-compensated or even in the optional humidity-optimized mode.This operating condition occurs, for example, when the target gas concentration is measured in a completely or at least largely enclosed space, for example in a measuring chamber.

[0023] In many cases, the invention eliminates the need to compromise so that the gas measuring device can be used for every possible operating condition. This compromise may result in the device not providing a sufficiently good measurement result under some operating conditions.

[0024] The invention can be used in combination with at least one sensor for an ambient condition. However, the invention eliminates the need for the gas measuring device to include a sufficiently reliable sensor for each ambient condition, i.e., a temperature sensor, a humidity sensor, and a pressure sensor.

[0025] In one embodiment, the gas measuring device can be operated selectively in any of at least two, optionally four, different modes. Preferably, the mode in which the gas measuring device is operated is set exclusively by adapting the evaluation unit, i.e., generally by adapting the software. For example, at least one calculation rule used by the evaluation unit to derive the target gas concentrations from signals is adapted accordingly. However, the hardware can often remain the same for every possible mode in which the gas measuring device is used. This makes it possible to manufacture several identical gas measuring devices and then configure each of these identical devices for the respective mode.This approach is in many cases more reliable, especially due to the possibility of serial production, than using gas measuring devices with different hardware components for the different modes.

[0026] It is possible for a gas measuring device to be pre-adjusted to a mode, i.e., during calibration and / or adjustment of the gas measuring device. In an alternative embodiment, the gas measuring device additionally comprises a selection unit. A user uses this selection unit to select one of at least two different possible modes. The gas measuring device is then operated in this mode. The user can later select a different mode. This embodiment makes it possible to use the same gas measuring device consecutively for different operating conditions without having to replace any component of the gas measuring device.

[0027] It is also possible for the gas measuring device to automatically switch from one mode to another and to measure an estimated value for the target gas concentration in each possible mode one after the other.

[0028] As already mentioned, the detector detection variable depends not only on the target gas concentration, but also on ambient conditions, in particular the ambient temperature, the ambient humidity, and the ambient pressure. In one embodiment, the gas measuring device additionally comprises at least one sensor for an ambient condition, in particular a temperature sensor. The temperature sensor of the gas measuring device is capable of measuring a measure of a temperature in the environment of the gas measuring device. The evaluation unit of the gas measuring device additionally uses a signal from the or each sensor for an ambient condition, for example a signal which is a measure of the measured ambient temperature. It is possible for the gas measuring device to comprise a sensor for each of at least two ambient conditions, and for the evaluation unit to use two signals from these two sensors to determine the target gas concentration.

[0029] In a preferred embodiment, the gas measuring device comprises a temperature sensor, but neither an ambient humidity sensor nor an ambient pressure sensor. This is advantageous in many applications, particularly for the following reason: Typically, both an ambient humidity sensor and an ambient pressure sensor come into chemical and mechanical contact with the environment and therefore age relatively quickly, at least if no suitable and often relatively expensive countermeasures are taken. A temperature sensor, on the other hand, can be chemically and mechanically separated from the environment.

[0030] In one embodiment, a sensor for an ambient condition can be selectively activated or deactivated, for example manually by a user or automatically by a control unit of the gas measuring device. For example, the control unit or a user deactivates a sensor for an ambient condition if it has been determined that this sensor is defective. Or a user or the control unit deactivates a sensor for an ambient condition if the gas measuring device is to be used in an environment that is or could be harmful to this sensor, or if this sensor consumes a lot of electrical energy or is unable to provide a reliable measured value for the ambient condition in this environment. For example, the gas measuring device comprises a temperature sensor that is permanently active, as well as a pressure sensor and / or a humidity sensor that is selectively activated or deactivated.

[0031] In a further development of this embodiment, the gas measuring device comprises a sensor for each relevant ambient condition, i.e., in particular, a sensor for the ambient temperature, for the ambient humidity, and for the ambient pressure. Each of these sensors can be activated and deactivated, preferably independently of any other sensor. Preferably, a user can selectively activate or deactivate each sensor for an ambient condition. The embodiment in which the gas measuring device comprises each sensor makes it easier to produce multiple gas measuring devices according to the invention. These gas measuring devices all have the same hardware and, in particular, comprise the sensors for the ambient conditions. To adapt a specific gas measuring device, it is sufficient to activate or deactivate individual sensors. It is not necessary to produce gas measuring devices with different hardware.

[0032] In one embodiment, the gas measuring device can be operated selectively in a mode selection state in which at least one of the two or even four modes according to the invention can be selected and applied, or in a standard state in which the evaluation unit determines the target gas concentration independently of a mode.

[0033] The design with these two states can be combined with the design in which at least one sensor for an environment is optionally activated or deactivated. One possible application of this combination is the following: The gas measuring device comprises a pressure sensor that is optionally activated or deactivated. When the pressure sensor is activated, the evaluation unit uses the signal from the pressure sensor to take into account the influence of the ambient pressure on the determination of the target gas concentration. When the pressure sensor is deactivated, the gas measuring device is operated at least temporarily in pressure-compensated mode. The same applies to a humidity sensor and the humidity-compensated mode. In the standard state, the gas measuring device can, for example, measure every ambient condition relevant to the measurement result. The corresponding sensor is therefore present and activated.

[0034] In one implementation, the gas measuring device is designed as a so-called catalytic converter. The detector comprises a heatable detector segment, and the gas measuring device is capable of heating the detector segment. In particular, the gas measuring device is capable of applying an electrical voltage to the detector segment, and the resulting current heats the detector segment. The heated detector segment oxidizes combustible target gas that has reached the detector as part of the gas sample—of course, only if this gas sample contains a sufficient amount of combustible target gas. The oxidation of the target gas releases thermal energy, and the released thermal energy increases the temperature of the detector segment. The temperature of the detector segment correlates with the target gas concentration.

[0035] The compensator comprises a heatable compensator segment. The gas measuring device is capable of heating the compensator segment. In a first alternative, the heated compensator segment is capable of oxidizing less combustible target gas per unit of time than the heated detector segment, ideally no combustible target gas at all. In another embodiment, the gas measuring device is configured as follows: Per unit of time, a smaller amount of the gas sample reaches the compensator than the detector. These two alternatives can be combined.

[0036] According to the invention, the gas measuring device comprises a detector detection variable sensor and additionally a compensator detection variable sensor. If the invention is applied to a catalytic converter, the gas measuring device is configured as follows: The detector detection variable sensor measures a measure of the temperature of the detector segment. The compensator detection variable sensor measures a measure of the temperature of the compensator segment. The evaluation unit determines the target gas concentration depending on - a signal from the detector detection size sensor, - a signal from the compensator detection quantity sensor, - preferably a signal from a temperature sensor and - optionally a signal from a humidity sensor and / or a signal from a pressure sensor.

[0037] In one implementation, a so-called bridge voltage is measured, which depends on both the voltage applied to the detector and the voltage applied to the compensator. The evaluation unit determines the target gas concentration based on the bridge voltage and, optionally, the signal from the temperature sensor.

[0038] Ideally, the compensator responds to ambient conditions in the same way as the detector, but is less affected or even not affected at all by a combustible target gas. This ideal condition is generally not achievable in practice.

[0039] The catalytic converter design eliminates the need to specify which target gases are likely to occur in the monitored area and should be detected. Typically, a catalytic converter can at least approximately determine the total concentrations of all combustible target gases.

[0040] The gas measuring device can also be designed differently than just described. For example, the gas measuring device comprises a radiation source or sound source capable of emitting electromagnetic radiation or sound, respectively, and a receiver as a detector capable of generating a signal depending on the intensity of the incident electromagnetic radiation or sound. The emitted radiation or sound penetrates a measuring chamber containing a gas sample to be examined. The measured intensity acts as the detector detection quantity. A target gas to be detected absorbs part of the radiation or sound in a specific wavelength range and therefore reduces the intensity of the incident radiation or influences the speed of the incident sound. The detector detection quantity sensor measures a measure of the intensity of the incident radiation or sound.

[0041] The invention can also be used in combination with a photoacoustic or electrochemical sensor.

[0042] A preferred implementation of such a gas measuring device is described below. The radiation source emits electromagnetic radiation. The detector is a photodetector that generates a signal depending on the intensity of incident electromagnetic radiation and is referred to below as the target gas photodetector. The signal of the target gas photodetector depends not only on the target gas concentration but also on at least one environmental condition. For example, both the target gas and water droplets and / or particles in the environment, and thus in the gas sample, absorb electromagnetic radiation.

[0043] Typically, the target gas to be detected absorbs electromagnetic radiation in a specific wavelength range. Therefore, a wavelength filter is preferably arranged between the radiation source and the photodetector, which exclusively or at least predominantly allows only radiation in the wavelength range in which the target gas attenuates the electromagnetic radiation to pass through.

[0044] However, the wavelength range of the target gas may overlap with a wavelength range in which water droplets and / or particles attenuate radiation. Furthermore, a signal from the target gas photodetector may also be influenced by the ambient humidity and / or ambient pressure. In a preferred implementation, the gas measuring device therefore additionally comprises a reference photodetector, which functions as the compensator detection quantity sensor. A further wavelength filter allows electromagnetic radiation in the wavelength range in which water droplets and / or particles attenuate radiation to pass through. The evaluation unit determines the target gas concentration based on a signal from the target gas photodetector and a signal from the reference photodetector. It is also possible to provide two different radiation sources emitting electromagnetic radiation in different wavelength ranges instead of two wavelength filters.

[0045] The preferred embodiment has already been explained, whereby the gas measuring device can be adapted to the respective mode solely by adjusting or modifying the evaluation unit. In one embodiment, a software program is adapted, which the evaluation unit uses to determine the target gas concentration.

[0046] In one embodiment, the evaluation unit has permanent or at least temporary read access to a computer-evaluable model. This model is stored, for example, in a data memory of the gas measuring device or is part of a program used by the evaluation unit. The model comprises a functional relationship for the or for each mode in which the gas measuring device can be operated. The functional relationship for a mode describes a relationship between - the target gas concentration on the one hand and - each detection quantity, i.e. the respective signal of each detection quantity sensor, preferably the ambient temperature, i.e. the signal from the temperature sensor, as well as optionally the signal of the humidity sensor and / or the signal of the pressure sensor on the other hand.

[0047] For example, the signal of the detector detection quantity sensor and the signal of the compensator detection quantity sensor occur in the functional model, as well as preferably the signal of the temperature sensor and optionally the signal of the humidity sensor and / or the signal of the pressure sensor.

[0048] At any given time, the gas measuring device is operated in one mode. To determine the target gas concentration in this mode, the evaluation unit applies the functional relationship valid for this mode to the respective signal of each detection parameter sensor, with preference given to the signal of the temperature sensor. The evaluation unit thus provides a determined target gas concentration as the measurement result.

[0049] Furthermore, the invention relates to a calibration device and a calibration method by means of which a gas measuring device can be calibrated according to the embodiment just described, i.e. with the functional model.

[0050] The calibration device is capable of capturing a specification, preferably from a user. The captured specification specifies at least one mode in which the gas measuring device to be calibrated should be operable. It is possible for the specification to specify at least two different modes.

[0051] The calibration device can automatically generate a computer-analyzable model. The generated model can be applied by the evaluation unit of the gas measuring device. For the or each mode specified in the recorded specification, the generated model includes a functional relationship. The functional relationship for a mode describes, in computer-analyzable form, a relationship between - the target gas concentration on the one hand and - the respective signal of each detection quantity sensor and preferably the signal of the temperature sensor and optionally a signal of another sensor for an environmental condition on the other hand.

[0052] To generate the model, the calibration device applies a given sample and a set of given possible relationships. In one implementation, each given possible functional relationship has at least one parameter, and the calibration device determines a value for each parameter. A parameter value is inserted for the or each parameter in each possible functional relationship.

[0053] The specified sample is determined empirically in advance and comprises several sample elements, namely at least one reference sample element, at least one pressure sample element, and at least one humidity sample element. Each sample element comprises an identifier for an ambient conditions-target gas combination, a signal value combination, and an actual target gas concentration. The ambient conditions-target gas combination is a combination of an ambient temperature, an ambient pressure, an ambient humidity, and an actual target gas concentration. The signal value combination contains a value for the respective signal of each detection variable sensor and, optionally, for the temperature sensor signal, which is measured at the ambient conditions-target gas combination of the sample element.The actual target gas concentration of the sample element is specified or measured with another device and leads to the signal values ​​of the detection quantity sensors.

[0054] The calibration device is designed to perform the following steps for each mode and for each sample element: - Every possible functional relationship is applied to the signal value combination of the sample element. This results in a resulting value for the target gas concentration being calculated. - The calculated value for the target gas concentration is compared with the actual value of the target gas concentration in this sample element.

[0055] Furthermore, the calibration device is designed to perform the following steps for each mode: - One of the predefined possible functional relationships is selected as the functional relationship actually used for this mode. To select a possible functional relationship, the comparison results are used—that is, the results of the comparison between the calculated and actual target gas concentration in the sample elements. For example, the functional relationship for which the calculated value for the target gas concentration deviates the least from the actual value is used. - The selected functional relationship is used by the evaluation unit as the functional relationship that is actually applied in this mode.

[0056] This design allows for empirical calibration. It is not necessary to specify a complete analytical model that the evaluation unit uses.

[0057] A further development of the embodiment with the functional model relates to an arrangement with a first and a second gas measuring device according to the invention. The first gas measuring device can be operated in pressure-compensating mode, the second gas measuring device in humidity-compensating mode. The evaluation unit of the first gas measuring device has read access to a first computer-evaluable model, and the evaluation unit of the second gas measuring device has read access to a second computer-evaluable model. The first computer-evaluable model describes a dependence of the target gas concentration on the or each detection variable and preferably on the ambient temperature, and the gas measuring device meets the requirements for operation in pressure-compensating mode when using the first model.The second computer-analyzable model also describes a dependence of the target gas concentration on the or each detection variable and preferably on the ambient temperature and meets the requirements for operation in humidity-compensated mode.

[0058] The gas measuring device according to the invention can be configured as a mobile device, wherein a user carries this device with them while they are in an area. The device informs the user about the concentration of at least one target gas in the spatial area. The mobile device preferably has its own power supply unit and its own output unit. The gas measuring device according to the invention can also be configured as a stationary device that is installed in a specific location-like area and preferably transmits messages with measured target gas concentrations to a spatially distant receiver.

[0059] In the following, the invention is described using an exemplary embodiment. Fig. 1 schematically shows an exemplary embodiment of the gas measuring device; Fig. 2 an exemplary design of the detector as a pellistor; Fig. 3 an exemplary different design of the detector as a flat component; Fig. 4 the detector of Fig. 3 in a plan view; Fig. 5 a boundary condition for the dependence on the ambient temperature; Fig. 6 a boundary condition for the dependence on ambient pressure; Fig. 7 a boundary condition for the dependence on the ambient humidity; Fig. 8 shows two exemplary measurement curves depending on the gain factor for the compensator; Fig. 9 a calibration device which adapts two gas measuring devices to two different modes.

[0060] In the exemplary embodiment, the gas measuring device according to the invention and the gas measuring method according to the invention are capable of monitoring a spatial area for the presence of at least one combustible target gas and / or of at least approximately determining the concentration of a combustible target gas in this area. In one application, the gas measuring device is capable of determining a measure of the sum of the target gas concentrations when multiple combustible target gases are present. The gas measuring device uses a method known from the prior art to analyze a gas mixture in the spatial area.

[0061] In the exemplary embodiment, the gas measuring device is designed as a stationary device that, during use, is arranged at a specific location in the area to be monitored. It is possible for several stationary gas measuring devices to be arranged in this area. The or each gas measuring device is at least temporarily in a data connection with a spatially distant receiver and transmits at least one signal to this receiver. The data connection is preferably a wireless data connection, i.e., implemented using radio waves. A wired data connection is also possible.

[0062] A detector is located inside the housing of the gas measuring device. A gas sample diffuses through an opening in the housing from the area to be monitored into the interior of the housing or is drawn into the interior, e.g., by a pump.

[0063] In the exemplary embodiment, the gas measuring device is designed as a catalytic converter. Its principle was described above. The invention can also be applied to a gas measuring device comprising a photo-optical, photo-acoustic, or electrochemical sensor.

[0064] The detector of the catalytic converter comprises an electrically conductive wire with a heating segment. The heating detector segment is, for example, a coil that forms a segment of the wire. The electrically conductive material is, for example, platinum, rhodium, or tungsten, or an alloy using at least one of these metals. An electrical voltage U is applied to this wire, causing an electrical current to flow through the wire. The flowing current heats the heating detector segment, and the heated heating detector segment releases thermal energy. The released thermal energy causes at least one combustible target gas to be oxidized inside the housing—of course, only if the spatial area, and thus the gas sample inside, contains combustible target gas.

[0065] In one application, methane (CH 4) a combustible target gas to be detected. By supplying heat energy, methane reacts with oxygen, producing water and carbon dioxide. From CH 4 and 2 O 2 becomes 2 H 2 O and CO 2 .

[0066] During the oxidation of the target gas, heat energy is released inside the housing. This heat energy acts on the detector and increases the temperature of the heated wire through which current flows. This temperature increase correlates with the released heat energy and thus with the concentration of the target gas inside the housing.

[0067] The temperature change changes a property of the detector that correlates with the detector temperature, for example the electrical resistance R of the detector wire through which the current flows. For many electrically conductive materials, the electrical resistance is known to be higher the higher the temperature of the conductive material. The gas measuring device measures at least one measurable quantity that is influenced by the property and thus by the detector temperature and which is referred to below as the "detection quantity". The detection quantity is, for example, directly the temperature or a quantity that correlates with the electrical resistance R of the wire, for example the electrical voltage U applied to the detector or the current I or the electrical power P absorbed by the detector wire.If another measurable quantity, which also depends on the electrical resistance R, is kept constant, the measured detection quantity U or I or P correlates with the desired concentration of the target gas. If, for example, the current I flowing through the detector is kept constant, the electrical voltage U applied to the detector correlates with the electrical resistance R of the wire. The resistance R correlates with the temperature of the wire. The temperature of the wire correlates with the target gas concentration. Thus, the measured electrical voltage U correlates with the desired target gas concentration - or, if multiple target gases are present, with the combination (sum) of the target gas concentrations.

[0068] Fig. 1 shows an exemplary embodiment of a gas measuring device 100 according to the invention, which is capable of monitoring a spatial area B for the presence of at least one combustible target gas. In this embodiment, a detector 10 is arranged in a detector chamber 8. A compensator 11, described further below, is arranged in a compensator chamber 5. The two chambers 8, 5 are arranged in a housing 4. The detector chamber 8 and thus the detector 10 are in fluid communication with the area B to be monitored via an opening Ö1. The compensator chamber 5 and thus the compensator 11 are in fluid communication with the area B via an opening Ö2. Thanks to the openings Ö1, Ö2, a gas sample Gp from the area B can reach the interior of the housing 4 and from there to the two chambers 8, 5.

[0069] An optional flame protection 2, for example a metallic grid, in front of the openings Ö1, Ö2 reduces the risk of flames escaping from a chamber 8, 5. Optionally, a thermal barrier (not shown) inside the gas measuring device 100 thermally separates the detector 10 from the compensator 11.

[0070] The electrical voltage U10 applied to detector 10 causes an electrical current to flow. The flowing current heats the heating detector segment 20 to an operating temperature, which is often between 400 °C and 500 °C. However, this operating temperature alone is generally not sufficient to oxidize a combustible target gas in the inner housing 1. A higher operating temperature is often undesirable because it could lead to uncontrolled combustion or decomposition, or even explosion, of the combustible target gas, which is often undesirable, and also consumes more electrical energy.

[0071] In order to be able to oxidize a combustible target gas despite an operating temperature below 500 °C, the detector 10 comprises a catalytic material which, in conjunction with the heated detector segment 20, oxidizes the target gas. Therefore, a gas measuring device with such a detector 10 is also referred to as a "catalytic sensor."

[0072] In a frequently used implementation, the heating detector segment 20 is surrounded by electrical insulation, for example, a ceramic sheath. This electrical insulation electrically insulates the heating detector segment 20 and, in particular, prevents unwanted short circuits. The electrical insulation is thermally conductive so that the heating detector segment 20 can release thermal energy into the surroundings of the detector 10, and conversely, thermal energy inside the detector chamber 8 can further heat the heating detector segment 20. A coating of a catalytic material is applied to this electrical insulation. Or a catalytic material is embedded in the electrical insulation. This catalytic coating comes into contact with the gas mixture in the detector chamber 8 and thus also with a combustible target gas. A detector 10 constructed in this way is often referred to as a "pellistor."

[0073] Fig. Figure 2 shows an example of a detector 10 designed as a pellistor and schematically the conversion of methane (CH 4 ) in CO 2 and H 2 O. The detector 10 comprises - a spirally wound and electrically conductive wire 20, which acts as a heating detector segment and is made of platinum, for example, - a ceramic casing 25, which surrounds the heating detector segment 20 and in the example shown has the shape of a solid sphere, - a catalytic coating on the outer surface of the ceramic casing 25, which Fig. 2 is indicated by circles 26, - a mounting plate 27 and - electrical contacts and mechanical supports 24 for the wire 20.

[0074] For example, platinum, palladium, or rhodium, or an alloy containing at least one of these materials, is used as the catalytic material. Alternatively or in addition to the catalytic coating, catalytic material 26 can also be embedded in the ceramic casing 25.

[0075] In a preferred embodiment, the solid sphere of the detector 10 has a porous surface with a catalytic coating 26. In one embodiment, this porous surface is manufactured as follows: The detector 10 with the porous surface but without the catalytic coating is provided. The catalytic coating 26 is applied to the porous surface, and a portion of the catalytic material penetrates into the interior of the detector 10. Thanks to this porous surface, the detector 10 has a larger surface area compared to a smooth surface. Thanks to this larger surface area, the detector 10 is better able to oxidize combustible target gas, in particular because a larger amount of target gas comes into contact with the catalytic material. Thanks to the porous surface, a gas can penetrate into deeper layers of the detector 10.

[0076] In one embodiment, the compensator 11 is constructed in the same way as the detector 10 and also includes a heating segment, designated by reference numeral 38. However, in one embodiment, a smaller amount of gas can reach the compensator 11 per unit of time than the detector 10. In another embodiment, the compensator 11 does not include a catalytic coating 26 or includes a catalytic coating 26 that is capable of oxidizing less target gas per unit of time than the detector 10.

[0077] Fig. 3 and Fig. 4 show a different design of the detector 10 in a perspective view ( Fig. 3) or in a top view ( Fig. 4). The detector 10 comprises the following components: - an electrically conductive component 30 with a heating segment 32 and an electrical contact 46, the component 30 having the shape of a conductor track, - a protective layer 35, - a support plate 31 extending in a plane, said plane being inclined to the plane of the drawing of Fig. 3 and in the plane of Fig. 4 lies, - a wafer substrate 33 which supports the carrier plate 31, and - electrical contact points 34 for the electrically conductive component 30.

[0078] The protective layer 35 covers at least the conductor track 30, preferably the entire carrier plate 31, and prevents the conductor track 30 from coming into direct contact with a gas mixture. In one embodiment, the protective layer 35 is made of silicon nitride. A catalytically active material is applied to the protective layer 35, at least in a region above the heating segment 32.

[0079] The compensator 11 can in turn be constructed in the same way as the detector 10 of Fig. 3 or and Fig. 4 or less or even no catalytically active material.

[0080] The temperature of the detector 10 and thus also the detection variable(s) is influenced not only by the released heat energy but also by the ambient conditions in the area B to be monitored. The three essential ambient conditions are the ambient temperature Temp, the ambient pressure P and the ambient humidity Hum. In particular, both the zero point of the detector 10 and the increase in the detector temperature depend not only on the target gas concentration but also on the ambient temperature Temp. These three ambient conditions Temp, P, Hum can also change the conditions inside the housing 4 and thus also in the detector chamber 8. These ambient conditions can namely also influence the detector temperature and thus a detection variable U10, for example because the thermal conductivity in the area surrounding the detector 10 is changed.It is desired that the gas measuring device 100 is, on the one hand, capable of reliably detecting a combustible target gas despite varying ambient conditions and, on the other hand, generates only a few false alarms, i.e., only rarely decides that a target gas is present even though in reality no target gas has occurred above a detection limit, which is an erroneous result.

[0081] Note: The three environmental conditions temperature, pressure, humidity are designated Temp, P, Hum, values ​​of these three environmental conditions are designated temp, p, hum.

[0082] The gas measuring device 100 according to the invention is capable of computationally compensating, to a certain extent, the influence of the three ambient conditions Temp, P, Hum on the detection variable. In the following description, the current I.1 is kept constant by closed-loop control, and the electrical voltage U10 applied to detector 10 acts as the detection variable. As already mentioned, this detection variable U10 depends on the temperature of the heating detector segment 20. This temperature, in turn, depends on the target gas concentration on the one hand and on the three ambient conditions just mentioned on the other.

[0083] In order to compensate for the influence of ambient conditions, the gas measuring device 100 comprises, in addition to the detector 10, the already mentioned compensator 11 in the compensator chamber 5, cf. Fig. 1. The compensator 11 also includes a wire with a heating compensator segment 38. An electrical voltage U11 is also applied to the compensator 11, causing an electrical current I.2 to flow and heating the heating segment 38 of the compensator 11. The compensator 11 is also exposed to varying environmental conditions.

[0084] In one embodiment, the compensator 11 also includes a spirally wound and electrically conductive wire, which functions as a heating compensator segment and is designated by reference numeral 38. The compensator 11 also includes a ceramic casing, a mounting plate, electrical connections, and mechanical supports. In one embodiment, however, the ceramic casing of the compensator 11, unlike the detector 10, is not provided with a catalytic coating.

[0085] In another embodiment, the compensator 11 is constructed in the same way as the detector 10, thus also comprising a ceramic coating. This ceramic coating is also catalytically active in the other embodiment. However, the gas measuring device 100 is designed such that less gas can reach the compensator 11 from the region B to be monitored than the detector 10 in a unit of time.

[0086] It is also conceivable that the heating segment 38 of the compensator 11 is heated to a lower temperature than the heating segment 20 of the detector 10.

[0087] Fig. Figure 1 shows the compensator 11 in the compensator chamber 5. It can be seen that the detector 10 comprises the heating detector segment 20, and the compensator 11 comprises the heating compensator segment 38. In the example shown, the compensator 11 is also designed as a spherical pellistor, but unlike the detector 10, it does not comprise a catalytically active coating 26.

[0088] According to the form of implementation, which is Fig. As shown in Figure 1, the detector 10 and the compensator 11 are supplied with electrical energy independently of one another. A first electrical circuit connects the detector 10 to a first voltage source 43, and a second electrical circuit connects the compensator 11 to a second voltage source 44. The two voltage sources are preferably implemented with rechargeable batteries (accumulators). It is possible for the same voltage supply unit to function as both the first voltage source 43 and the second voltage source 44.

[0089] A voltage sensor 12.1 measures the electrical voltage U10 applied to detector 10. A current sensor 13.1 measures the strength I.1 of the electrical current flowing through the circuit for detector 10. A voltage sensor 12.2 measures the electrical voltage U11 applied to compensator 11. A current sensor 13.2 measures the strength I.2 of the electrical current flowing through the circuit for compensator 11.

[0090] Ideally, a combustible target gas only affects detector 10, while the ambient conditions affect both detector 10 and compensator 11 in the same way. If these ideal conditions are met, the difference between the detector detection value U10 and the compensator detection value U11 is a reliable measure of the desired concentration of the target gas, for every possible combination of ambient conditions. However, this ideal condition is generally not met in practice. One reason for this is that detector 10 and compensator 11 react differently to ambient conditions due to design differences and / or unavoidable manufacturing tolerances. These differences are particularly relevant if compensator 11 contains less catalytically active material than detector 10 or even no catalytically active material at all.Another reason is that the oxidation of target gases often leads to greater deposits on the surface of the detector 10 than on the surface of the compensator 11. An embodiment according to the invention is described below as to how the gas measuring device 100 is able to reliably measure the target gas concentration in many cases despite these different environmental conditions.

[0091] According to a preferred embodiment, the gas measuring device 100 measures the ambient temperature, preferably at a measuring position on a surface of the gas measuring device 100. The invention can also be implemented without the gas measuring device 100 comprising a temperature sensor.

[0092] In the illustrated embodiment, a temperature sensor 14 of the gas measuring device 100 is capable of measuring a measure of the ambient temperature Temp. In the exemplary embodiment, the temperature sensor 14 provides a measure of the temperature difference ΔTemp between the current ambient temperature and a predetermined reference temperature of, for example, 20 degrees C. The temperature sensor 14 provides an analog or digital signal that correlates with the ambient temperature Temp—in the exemplary embodiment, with the temperature difference ΔTemp. The influence of the ambient temperature Temp on the detection variable is computationally compensated to a certain extent with the help of a signal from the temperature sensor 14.

[0093] The gas measuring device 100 from Fig. 1 comprises, in one implementation, a sensor 17 for the ambient pressure P and a sensor 18 for the ambient humidity Hum. The sensors 17, 18 can be constructed relatively simply in one application, so that the ambient humidity Hum and / or the ambient pressure P can only be measured with a relatively large measurement error. In another application, each sensor 17, 18 can be activated and deactivated. For example, a user switches off a sensor 17 or 18 if the gas measuring device 100 can be used in an environment in which the activated sensor 17 or 18 can be damaged, for example due to very high pressure or a specific gas in the environment. It is also possible that a sensor 17, 18 is defective and the gas measuring device 100 should still be used.

[0094] How the influence of the ambient pressure P and the ambient humidity Hum are nevertheless compensated at least to a certain extent is described below.

[0095] The preferred embodiment, in which the gas measuring device 100 comprises a reliable sensor 14 for the ambient temperature Temp, but only a relatively simple and / or deactivatable sensor 18 for the ambient pressure P and a relatively simple and / or deactivatable sensor 17 for the ambient humidity Hum, has the particular advantage described below: A temperature sensor 14 can be chemically insulated from the environment, specifically by insulating material with good thermal conductivity. The temperature sensor 14 can measure the ambient temperature Temp relatively reliably, but is not exposed to the other ambient conditions. Both a pressure sensor and a humidity sensor, on the other hand, must generally be in fluid communication with the environment, i.e., with the spatial area B to be monitored, and can therefore be exposed to flammable target gases and other potentially harmful substances over a very long period of time.A sensor that is fluidly connected to the environment and yet sufficiently robust and reliable is often relatively expensive and / or heavy and / or requires a relatively high electrical power consumption. A temperature sensor does not have this disadvantage, or at least only to a lesser extent.

[0096] A schematically shown control unit 6 with an evaluation unit 9 receives signals from sensors 12.1, 12.2, 13.1, 13.2, 14 and derives an estimated value for the current concentration of a combustible target gas in the monitored area B. This estimated value generally varies over time. If multiple combustible target gases are present in area B, the estimated value describes the summed concentrations of these combustible target gases. The control unit 6 and thus the evaluation unit 9 have at least temporary read access to a data memory 7 in which an evaluation program and / or a computer-analyzable model Mod with multiple functional relationships are stored.

[0097] Ideally, the gas measuring device 100, with the aid of the compensator 11 and the temperature sensor 14, would fully compensate for the influence of all three environmental conditions, i.e., the influence of the ambient temperature Temp, the influence of the ambient pressure P, and the influence of the ambient humidity Hum. However, this is generally not possible in practice, at least not if the ambient pressure P and / or the ambient humidity Hum can vary considerably during use and neither a pressure sensor nor a humidity sensor is present and activated. A key reason for this is that in many cases the compensator 11 and the detector 10 react differently to at least one environmental condition, in particular due to design-related or construction-related differences or unavoidable manufacturing tolerances.

[0098] The gas measuring device 100 of the exemplary embodiment can be selectively operated in one of four possible different modes. A switch 16 is shown as an example, with which a user can select one of these four possible modes. In one embodiment, one of these four modes is selected during configuration of the gas measuring device 100 and implemented using appropriate software. The model Mod in the data memory 7 is then valid for this selected mode. The gas measuring device 100 cannot necessarily be switched from one mode to another during operation.

[0099] In another embodiment, a user actuates switch 16 to switch from one mode to another. This switch 16 can be implemented, for example, as a mechanical switch or with the aid of a touchscreen or multiple buttons. A model for each mode is then stored in the data memory 7.

[0100] In a further embodiment, the gas measuring device 100 automatically switches from one mode to the other during operation, so that it operates in each of the possible modes during use. In each mode, the gas measuring device 100 determines an estimated value for the target gas concentration. As a rule, the estimated values ​​differ from mode to mode. A preferred embodiment for deriving an estimated value and preferably displaying it to a user is the following: As long as an estimated value determined in a mode lies within a predetermined target concentration range, this estimated value is output. Or no message is output at all, or the message is output that no impermissible target gas concentration is present.If, however, at least one estimated value lies outside the specified target concentration range, the estimated value furthest from the specified target concentration range is output, i.e., the largest estimated value of a dangerous target gas or the smallest estimated value of a vital target gas, e.g., oxygen. With this configuration, you're on the safe side.

[0101] In the example, the following four modes are distinguished: P The influence of the ambient pressure P is compensated as best as possible (pressure-optimized mode). Hum The influence of the ambient humidity Hum is compensated as best as possible (humidity optimized mode). P_Hum The influence of the ambient pressure P is compensated as well as possible while maintaining a boundary condition concerning the ambient humidity Hum (pressure compensating mode). Hum_P the influence of the ambient humidity is compensated as well as possible while maintaining a boundary condition concerning the ambient pressure P (humidity compensating mode).

[0102] The boundary condition concerning the ambient humidity Hum is predefined and, for example, specifies that the measured value con for the target gas concentration Con varies by a maximum of x% if the ambient humidity Hum remains within a specified humidity range. During use, the ambient humidity Hum always lies within this humidity range. The same applies to the boundary condition concerning the ambient pressure P.

[0103] The gas measuring device 100 can therefore be operated in one of four possible modes. This allows the gas measuring device 100 to be adapted to different operating conditions.

[0104] One possible application condition is the following: The target gas concentration is to be measured in a pipe with a gas mixture flowing through it. Under this application condition, the ambient pressure P can fluctuate significantly, which is why the P mode or the P_Hum mode is appropriate.

[0105] Another possible application condition is the following: The target gas concentration in an enclosed space is to be measured. This enclosed space is only fluidly connected to the environment via a relatively small opening. Or the enclosed space is a test chamber in which different environmental conditions, and in particular different humidities, are created to test a component. Under these other application conditions, the ambient humidity Hum can fluctuate significantly, which is why the Hum or Hum_P mode is useful.

[0106] The invention makes it possible to produce a set of identical gas measuring devices and to adapt each gas measuring device 100 of this set to the respective application condition by selecting one of the four possible modes. Operation in a specific mode requires the implementation or selection of software, while the hardware remains unchanged. This configuration increases reliability in many cases and reduces construction costs compared to a configuration in which at least two sets of different gas measuring devices are produced, one set for each application condition.

[0107] In the following illustration, the electrical detector voltage U10 applied to detector 10 acts as the detection variable, which correlates with the temperature of the heating segment 20 of detector 10. The current I1 is kept constant. Accordingly, the electrical compensator voltage U11 applied to compensator 11 acts as the detection variable, which correlates with the temperature of the heating segment 38 of compensator 11. The current I2 is kept constant.

[0108] The three sensors 14, 17, and 18 also each provide an electrical signal—of course, only when they are intact and activated. This signal is designated U(ΔTemp), U(Hum), and U(ΔP), respectively. The exemplary embodiment assumes that the three environmental conditions—ambient temperature Temp, ambient humidity Hum, and ambient pressure P—each have a linear effect on the detection variables. Therefore, a proportionality factor is determined in advance for each of these three environmental conditions, preferably empirically, and used during operation.

[0109] The evaluation unit 9 calculates a value for a total detection quantity Det depending on the values ​​for the five variables U10, U11, U(ΔTemp), U(Hum), U(ΔP). The evaluation unit 9 applies the calculation rule Det=F[U10,U11,U(ΔTemp),U(Hum),U(ΔP)] In one embodiment, the function F depends on at least one parameter for U10 and U11, optionally on at least one further parameter. In a preferred implementation of this embodiment, the calculation rule (1) has the form Det=U10−α*U11−β*U(ΔTemp)−γ*U(Hum)−ξ*U(ΔP)−x0. with an amplification factor α for the compensator voltage U11, an amplification factor β for the signal U(ΔTemp) of the temperature sensor 14 and a zero value x0. The amplification factor α compensates to a certain extent for design-related differences between the detector 10 and the compensator 11 and is preferably greater than 1.1. The amplification factor β compensates to a certain extent for the assumed linear influence of the ambient temperature Temp on the overall detection variable Det. Accordingly, the factors γ and ξ compensate for the also assumed linear influence of the ambient humidity Hum and the ambient pressure ΔP.

[0110] If neither a humidity sensor 17 nor a pressure sensor 18 is present or both sensors 17, 18 are deactivated or defective, the following calculation rule is applied: Det=U10−α*U11−β*U(ΔTemp)−x0.

[0111] The parameters of the function F are calculated empirically using a sample. It is also possible that the function F takes the form of a neural network or is generated by another learning process.

[0112] From the value for the total detection quantity Det, the evaluation unit 9 calculates a value for the target gas concentration Con and applies the calculation rule Conmeas=FCon(Det) For example, Conmeas=γCon*Det with an empirically determined factor γ Con Note: Con denotes the actual target gas concentration, Con meas the measured quantity. Ideally, Conmeas = Con.

[0113] Both the function F and the function F Con are stored in a suitable computer-evaluable manner in the data memory 7 and form part of the model Mod.

[0114] Depending on the mode used, the evaluation unit 9 uses a function F as function F in the calculation rule (1) P , F P_Hum , F Hum or F Hum_P If the calculation rule (2) or (3) is applied, then depending on the mode, the gain factor α for the compensator voltage U11 is a gain factor α P , α P_Hum , α Hum or α Hum_P applied. Accordingly, the gain factor β for the signal U(ΔTemp) of the temperature sensor 14 is an amplification factor β P , β P_Hum , β Hum or β Hum_Papplied. In one embodiment, four different zero values ​​are applied, while in another embodiment, the same zero value x0 is always applied regardless of the mode.

[0115] Fig. 5 to Fig. 7 illustrate given boundary conditions for how the measured value Con meas for the target gas concentration Con from the temperature difference ΔTemp ( Fig. 5), from the ambient pressure P ( Fig. 6) or the ambient humidity Hum ( Fig. 7). In this example, the calculation rule (3) with the gain factors of α = 1.8 and β = -1.11 as well as the calculation rule (5) were applied. On the x-axis, the temperature difference ΔTemp in [degrees C] ( Fig. 5), the deviation ΔP of the ambient pressure P from a given reference pressure in [mbar] ( Fig. 6) or the ambient humidity Hum in [% rel. humidity]. On the y-axis, the deviation between the measured value con measand the actual target gas concentration con in [% LEL]. Shown are a tolerance band Tol Temp for the dependence on the ambient temperature Temp, a tolerance band Tol P for the dependence on the ambient pressure P and a tolerance band Tol Hum for the dependence on the ambient humidity Hum.

[0116] The following example describes how values ​​for the parameters of the calculation rule (2) are derived. This derivation assumes that the three ambient conditions Temp, P, Hum and the actual target gas concentration Con have independent effects on the total detection variable Det and thus on the measured target gas concentration Con. meas Furthermore, it is assumed that the ambient temperature Temp has an approximately linear effect on the total detection variable Det and thus on the measured target gas concentration Con measso that the influence of the ambient temperature Temp can be compensated with sufficient accuracy using the factor β. In many cases, these assumptions correspond sufficiently closely to reality.

[0117] First, a so-called zero-point adjustment is performed. This zero-point adjustment is explained using the example of calculation rule (2). Here, the gas measuring device 100 is subjected to a defined reference test environment Cond Ref exposed. The reference test environment Cond Ref has a reference concentration of Ref of target gas to be detected, a reference ambient temperature temp Ref , a reference ambient pressure p Ref and a reference ambient humidity hum Ref For example, con Ref = 0 and Hum Ref = 0%, the target gas concentration Con and the ambient humidity Hum therefore assume the lowest possible value.

[0118] In one implementation, the factor β Ref initially set to 0, ie the influence of the ambient temperature Temp and thus the signal U(ΔTemp) are initially neglected. The factor α Ref is initially set to 1, ie the total detection value Det depends on the difference between the two voltages U10 and U11. During the zero point adjustment, the factors α Ref and β Ref take other values. The zero value x0 is always set so that the total detection quantity Det and thus the measured target gas concentration Con meas for the reference test environment Cond Ref , i.e. in the absence of combustible target gas, take the value 0.

[0119] Subsequently, a value for the factor γ Con determined in the calculation rule (5). The reference test environment Cond Refis modified in such a way that it has successively different target gas concentrations con(1), ... For each target gas concentration con(1), ... the gas measuring device 100 provides a value det(1), ... for the total detection quantity Det. For this purpose, the gas measuring device 100 uses the just determined or set factors α Ref , β Ref and x0. This procedure yields a sample {[con(1), det(1)], ...}. The factor γ Con is determined using this sample through regression analysis.

[0120] Now at least one test environment compared to the reference test environment Cond Ref A modified test environment is created by changing at least one environmental condition. Fig. 8 and Fig. 9 illustrate an example of a procedure in which the gas measuring device 100 is exposed to two different defined test environments Cond Hum and Cond P is exposed. In Fig. 9 shows a calibration device 110 with a first component 110.1 and a second component 110.2 as well as a further gas measuring device 100.1, wherein the gas measuring device 100.1 is identical in construction to the gas measuring device 100.

[0121] The test environment Cond Hum has a significantly higher ambient humidity Hum than the reference test environment Cond Ref , while the other environmental conditions Con, Temp, P are the same. For example, the relative ambient humidity Hum in the reference test environment Cond Ref 0% and in the test environment Cond Hum 90%, this is the highest value at which the gas measuring device 100 can still be used. The test environment Cond P has a significantly increased or decreased ambient pressure P than the reference test environment Cond Ref , while the other environmental conditions Con, Temp, Hum are the same. For example, the test environment Cond Pan ambient pressure P higher by 200 mbar than the reference test environment Cond Ref .

[0122] The gas measuring device 100 provides in the test environment Cond Hum each have a value u10(Cond Hum ), u11(Cond Hum ), u(ΔTemp) (Cond Hum ) for the three signals U10, U11, U(ΔTemp), in the test environment Cond P each have a value u10(Cond P ), u11(Cond P ), u(ΔTemp) (Cond P ). First, the values ​​β Ref and γ Con , which have been determined or adjusted as just described. A value is determined for the gain factor α, which is described below. The zero value x0 is set so that in the reference test environment Cond Ref , i.e. in the absence of combustible target gas, a target gas concentration of zero is measured.

[0123] Fig. 8 shows two measurement curves 50 P , 50 Hum, which were generated with the same gas measuring device 100. The amplification factor α is plotted on the x-axis, and the resulting deviation of the measurement result con on the γ-axis. meas from the actual target gas concentration con in % LEL (Lower Explosion Level), whereby this deviation con meas - con depends on the amplification factor α. For this purpose, the calculation rules (3) and (5) were applied. Therefore, a positive or negative deviation of the measured target gas concentration Con meas from the actual target gas concentrations Con. The measurement curve 50 P was used in the test environment Cond P obtained, the measurement curve 50 Hum in the test environment Cond Hum .

[0124] It can be seen that the measurement curve 50 Hum the x-axis at α Hum = 1.2. This means: At the value α Hum= 1.2 for the gain factor α and the resulting zero value x0 Hum the gas measuring device 100 delivers the correct value 0 for the target gas concentration Con. This applies to the test environment Cond Hum In many cases, it is justified to assume that the value α Hum = 1.2 leads to a correct value for the target gas concentration Con even at a lower ambient humidity Hum. Subsequently, the value β, which compensates for the influence of the ambient temperature Temp, is adjusted, for example by exposing the gas measuring device 100 to a changed ambient temperature and the resulting measured value con meas This procedure yields a set α Hum , β Hum , x0 Hum of parameter values. This set of parameter values ​​is used for the humidity-optimized mode Hum

[0125] In Fig. 8 is based on the measurement curve 50 PIt can be seen that the humidity-optimized mode Hum leads to an incorrect measured value when the pressure P changes, namely to con meas - con = -8.5 LEL. This is acceptable in some applications, for example, when the gas measuring device 100 is used in a test chamber with widely varying ambient humidity Hum. In the humidity-compensated mode Hum_P, however, a specified boundary condition regarding the ambient pressure P should be maintained. The measured target gas concentration Con meas should differ from the actual target gas concentration Con by a maximum of 5% LEL at any ambient pressure P and therefore also at any pressure difference ΔP. This boundary condition is defined in Fig. 8 by a tolerance band Tol P = +- 5% LEL around the x-axis. The influence of the ambient humidity Hum should be compensated as best as possible in the humidity-compensating mode Hum_P while maintaining this boundary condition. Fig. 8, compliance with this boundary condition leads to a value α Hum_P = 1.8 LEL. A set of parameter values ​​α Hum_P , β Hum_P , x0 Hum_P for the humidity compensating mode Hum_P is derived.

[0126] The measurement curve 50 P intersects the x-axis at α P = 2.8. This value is used for the pressure-optimized mode P. A set of parameter values ​​α P , β P , x0 P for the pressure-optimized mode P is derived. For the pressure-compensated mode P_Hum, the boundary condition is used that the measured target gas concentration Con meas from the actual target gas concentration Con at any ambient humidity Hum by a maximum of 10% LEL. This boundary condition is defined in Fig. 8 through the tolerance band Tol Hum This boundary condition leads to a value α P_Hum= 2.3 for the pressure compensating mode P_Hum. A set of parameter values ​​α P_Hum , β P_Hum , x0 P_Hum for the pressure compensating mode P_Hum is derived.

[0127] As already explained, in many cases it is justified to assume that the target gas concentration Con affects the detection parameters U10, U11, U(ΔTemp) independently of the ambient conditions Temp, P, Hum. Therefore, the calculation rule (5) with the previously determined factor γ is preferred. Con It is also possible to use a factor γ Con to be determined empirically.

[0128] illustrates, by way of example, how two gas measuring devices 100 and 100.1 are calibrated using a calibration device 110 before their first use. The two gas measuring devices 100 and 100.1 are identical in construction and, in particular, have the same detectors and compensators. They are, for example, as described with reference to Fig. 1, but do not necessarily include a switch 16. The gas measuring device 100 is to be operated in the pressure-compensating mode P_Hum, the gas measuring device 100.1 in the humidity-compensating mode Hum_P. The calibration device 110 provides a set α P_Hum , β P_Hum , x0 P_Hum of parameter values ​​for the pressure compensating mode P_Hum and a set α Hum_P , β Hum_P , x0 Hum_P of parameter values ​​for the humidity-compensated mode Hum_P. To derive these two sets of parameter values, the gas measuring device 100 with the temperature sensor 14 is used. In addition, a humidity sensor 117 and a pressure sensor 118 are used to determine the respective test environment Cond Ref , Cond P , Cond Hum The two sensors 117 and 118 are robust and reliable and are used only for calibration and are not components of the gas measuring devices 100, 100.1.

[0129] In the procedure just described, the calculation rules (3) and (5) are used, and three different test environments Cond Ref , Cond P , Cond Hum are used. In many cases, this approach results in a gas measuring device 100, 100.1 that is capable of measuring the target gas concentration Con with sufficient accuracy in the respective mode. A more generally applicable approach is described below. This approach requires more effort and computing time.

[0130] First, the calibration for mode P is described, i.e. the mode in which the influence of the ambient pressure P is compensated as best as possible. In the Fig. In the position shown in Figure 1, switch 16 is set to this mode P.

[0131] The following example describes how the function F = F Pis determined empirically. A first sample of measured values ​​is determined. For the first sample of measured values, the following conditions are preferably established: No combustible target gas is present, ie, the target gas concentration is zero. The ambient humidity Hum remains constant. 0 for example 0%. The ambient pressure P takes on M different values ​​p(1), ..., p(M), the ambient temperature N different values ​​temp(1), ..., temp(N). Preferably N < M. It is possible that N equals 1, i.e. that the ambient temperature Temp is the same for all values ​​of the first sample of measured values. The M values ​​p(1), ..., p(M) for the ambient pressure P and the N values ​​temp(1), ..., temp(N) for the ambient temperature Temp are chosen so that they can actually occur in an application.

[0132] For the first sample of measured values, a total of M*N different conditions are created. Each condition x i,j(i=1,...,M; j=1,...,N) defines a constant target gas concentration con(1) [preferably con(1) equal to zero], an ambient pressure p(i), an ambient temperature temp(j), and the ambient humidity hum(1). The gas measuring device 100 is successively subjected to these M*N different conditions x 1,1 , ..., x M,N and the three detection variables U10, U11, U(ΔTemp) are measured. Each condition x i,j leads to three measured values ​​u10(x i,j ), u11(x i,j ), u(ΔTemp)(x i,j ) for the three variables U10, U11, U(ΔTemp). The first sample of measured values ​​consists of M*N sample elements, where each sample element has the form {[u10(xi,j),u11(xi,j),u(ΔTemp)(xi,j)];[p(i),Δtemp(j),hum(1)]} has.

[0133] As already explained above, the function F = F Pin the calculation rule (1) depends on several parameters Par(1), ..., Par(x), x >= 2. For example, if the calculation rule (3) is used, these are the x = 3 parameters α = α P , β = β P , x0 = x0 P or with a constant zero value x0 the two parameters α = α P and β = β P . If each parameter Par(1), ..., Par(x) in the function F P a value par(1), ..., par(x) is assigned and then the calculation rule (1) is applied to a triple [u10(x i,j ), u11(x i,j ), u(ΔTemp)(x i,j )] is applied, the application returns a value det(xi,j)=FP[u10(xi,j),u(xi,j),u(ΔTemp)(xi,j)] for the total detection size Det. This provides a first detection size sample with M*N sample elements, where each sample element has the form {det(xi,j);[u10(xi,j),u11(xi,j),u(ΔTemp)(xi,j)]} has (i=1,...,M; j=1,...,N).

[0134] When operating in P mode, the influence of the ambient pressure P should be computationally compensated as much as possible. This means: The total detection variable Det is set so that it depends as little as possible, ideally not at all, on the ambient pressure P. It is accepted that it depends relatively strongly on the ambient humidity Hum and at least somewhat on the ambient temperature Temp.

[0135] To define the total detection quantity Det for operation in mode P, x values ​​par(1), ..., par(x) for the x parameters Par(1), ..., Par(x) of the function F PEach set of parameter values ​​par(1), ..., par(x) leads to an empirical variance Var = Var[par(1), ..., par(x)] of the resulting first detection quantity sample. The parameter values ​​par(1), ..., par(x) are set such that they lead to a minimal empirical variance Var in the first detection quantity sample. To set the parameter values ​​par(1), ..., par(x), an objective function is numerically minimized. The variables of these objective functions are the x parameters Par(1), ..., Par(x) of the function F P . The objective function is a measure of the empirical variance Var of the total detection variable Det = F P [U10, U11, U(ΔTemp)].

[0136] This procedure is explained using the preferred embodiment in which the calculation rule (3) is used. Each triple of values ​​for the three parameters α P , β P , x0 Pleads to a value var for the empirical variance Var of the resulting first detection size sample. det(xi,j)=u10(xi,j)−αP*u11(xi,j)−βP*u(ΔTemp)(xi,j)−x0P

[0137] The objective function to be minimized is therefore the measure of the empirical variance Var of the total detection quantity Det = U10 - α P *U11 - β P *U(ΔTemp) - x0 P .as a function of the three parameters α P , β P , x0 P .

[0138] As a measure of the empirical variance Var, the difference between the largest value max {det(x i,j ), where i=1,...,M; j=1,...,N} and the smallest value min {det(x i,j ), where i=1,...,M; j=1,...,N} for the total detection quantity Det. It is also possible to use the following calculation rule: Var=1M*N−1∑i=1M∑j=1N[det(xi,j)−detavg]2 with detavg=1M*N∑i=1M∑j=1Ndet(xi,j)

[0139] The two-step procedure described below significantly reduces the computational effort. In many cases, it leads to a similarly good result for mode P.

[0140] The function F P the calculation rule (1) is simplified and divided into two functions, namely Det=FP,10,11[U10,U11]−FP,Temp[U(ΔTemp)].

[0141] The two functions F P,10,11 and F P,Temp depend on at least one parameter each. A special form of (12) is the calculation rule (3) with FP,10,11[U10,U11]=U10−αP*U11−x0P andFP,Temp[U(ΔTemp)]=βP*U(ΔTemp).

[0142] First, for the or each parameter of the function F P,10,11 In the design according to the calculation rule (3), a value is specified for each of the parameters α P and x0 PFor this purpose, a reduced first detection size sample is used in which the measured values ​​of the temperature sensor 14 are omitted. Each sample element of this reduced detection size sample has the form {[det(xi,j);[u10(xi,j),u11(xi,j)]}

[0143] Using this reduced first detection size sample, the respective value for the or each parameter of the function F P,10,11 set so that the measure of empirical variance Var is minimized.

[0144] Now the function F P,10,11 This function F P,10,11 is applied to the reduced detection size sample. More precisely: The function F P,10,11 is applied to the respective two values ​​u10(x i,j ), u11 (x i,j ) in each sample element of the form (8), namely {det(xi,j);[u10(xi,j),u11(xi,j),u(ΔTemp)(xi,j)]} applied. With the designation detP,10,11 (x i,j ) = F P,10,11 [u10(x i,j ), u11 (x i,j )] a reduced second detection size sample is generated in which each sample element has the form {det(xi,j);[detP,10,11(xi,j),u(ΔTemp)(xi,j)]} Using this sample, a value is determined for the or each parameter of the function F P,Temp In the case of the calculation rule (3), this is a value for the only parameter β P The or each value is again set so that the measure of variance Var is minimized.

[0145] For a further simplification, under typical ambient conditions and depending on a gain factor α, the zero value x0 P The ambient conditions are, for example, 20 degrees C, 1000 mbar, and 0% relative humidity. The two detection sample sizes just described are used to first determine the gain factor α Pfor the compensator voltage U11 and then the gain factor β P for the measured ambient temperature U(ΔTemp). The previously used zero value x0 is used without changing it.

[0146] Different variants of this approach are possible.

[0147] As described above, a first detection quantity sample is derived from the first measured value sample, where the first measured value sample has the form (6) and the first detection quantity sample has the form (7), and each sample has M*N sample elements. It is also possible to derive a first concentration sample with M*N sample elements from the first measured value sample, where each sample element has the form con(xi,j)=FCon{FP[u10(xi,j),u11(xi,j),u(ΔTemp)(xi,j)]} has (i=1,...,M; j=1,...,N).

[0148] In one embodiment, a second sample of measured values ​​is determined in addition to the first. Just as with the first sample of measured values, the ambient humidity Hum takes the constant value hum 0 , the ambient pressure PM various values, and the ambient temperature Temp N various values. In contrast to the first sample of measured values, however, combustible target gas is present in the environment. The function, which is derived empirically using the first sample of measured values, is denoted by F P,0 Using the second sample of measured values, a function F P,con The applied function F is derived by a suitable averaging of the two functions F P,0 and F P,con derived.

[0149] The configuration for the P_Hum mode is now described. The measured value con meas for the target gas concentration Con measshould vary by a maximum of x% depending on the ambient humidity Hum if the ambient humidity Hum remains within a specified humidity range.

[0150] Again, the first sample of measurements is used, i.e. a sample with sample elements, where each sample element has the form (6), i.e. {[u10(xi),u11(xi),u(ΔTemp)(xi)];[Δtemp(i),p(i),hum(1)]} The first sample of measured values ​​shows the same ambient humidity hum(x 1 ) before.

[0151] In addition, K-1 further sample values ​​are generated, K >=2. For every second sample, a value hum(2), ..., hum(K) is set for the ambient humidity Hum, whereby the total K values ​​hum(1), ..., hum(K) are all different from each other. The first sample was measured under M*N conditions x i,j,1 = x i,j(i=1,...,M*N) is generated, where the environmental conditions con(1), p(i), Δtemp(j), hum(1) are present (i=1,...,M; j=1,...,N). For each subsequent sample, the M*N conditions x i,j,k (i=1, ... , M; j=1, ... , N; k=2,...,K).

[0152] In total, there are K samples with M*N sample elements each, where sample no. k has the form {[u10(xi,j,k),u11(xi,j,k),u(ΔTemp)(xi,j,k)];[p(i),Δtemp(i),hum(k)]} (i=1,...,M; j=1,...,N; k=1,...,K).

[0153] In P_Hum mode, the evaluation unit 9 applies the calculation rule Det=FP_Hum[U10, U11, U(ΔTemp)] Preferably, the calculation rule (18) has the form Det=U10−αP_Hum*U11−βP_Hum*U(ΔTemp)−x0P_Hum.

[0154] For the x parameters Par(1), ..., Par(x) of the function F P_Hum values ​​must be calculated.

[0155] The derivation of a first detection size sample was described above with reference to the calculation rule (7). This procedure is modified. Accordingly, K detection size samples are derived. Each detection size sample has M*N sample elements, where each sample element has the form det(xi,j,k)=FP_Hum[u10(xi,j,k),u11(xi,j,k),u(ΔTemp)(xi,j,k)] has.

[0156] The above-mentioned boundary condition that the measured value con for the target gas concentration Con should vary by a maximum of x% depending on the ambient humidity Hum leads to a boundary condition for the total detection variable Det. This should vary by a maximum of y% depending on the ambient humidity Hum. The factor y depends on the specified functional relationship between the target gas concentration Con and the total detection variable Det, whereby this relationship is described by the calculation rule (4), in particular by the calculation rule (5). For example, the total detection variable Det should lie within a tolerance band of width y% with fluctuating ambient humidity Hum. This leads, for example, to the requirement (1−y)*detavg<=det(xi,j,k)<=(1+y)*detavg for all i=1,...,M;j=1,...,N;k=1,...,K), where det avg is the mean of all sample elements of the detection size sample(s).

[0157] The parameter values ​​par(1), ..., par(x) for the function F P_Hum the calculation rule (18) are determined in such a way that the boundary condition (21) is met. List of reference symbols 100 Gas measuring device, includes the detector 10, the compensator 11, the temperature sensor 14, the control unit 6 and the data memory 7 as well as optionally the humidity sensor 17 and the pressure sensor 18 2 optional flame protection in front of the openings Ö1, Ö2 5 Compensator chamber, surrounds the compensator 11 6 Control unit, receives signals from sensors 12.1, 12.2, 13.1, 13.2, 14 7 Data storage in which the model mod is stored 7.1 Data memory of the additional gas measuring device 100.1, in which the model Mod.1 is stored 8 Detector chamber, surrounds the detector 10 9 Evaluation unit, belongs to control unit 6, transmits the target gas concentration Con meas here 10 detector, includes the heating segment 20 11 Compensator, includes the heating segment 38 12.1 Voltage sensor, measures the voltage U10 12.2 Voltage sensor, measures the voltage U11 13.1 Current sensor, measures the current I.1 13.2 Current sensor, measures the current I.2 14 Temperature sensor, measures the difference ΔTemp between the ambient temperature and a reference temperature 16 Selection unit in the form of a switch with which a user can select a mode 17 Humidity sensor of the gas measuring device 100, measures the ambient humidity Hum 18 Pressure sensor of the gas measuring device 100, measures the pressure difference ΔP 20 heating segment of the detector 10 24 electrical contacts for the heating detector segment 20 25 Ceramic coating around the heating detector segment 20 26 catalytic coating on the ceramic coating 25 27 Detector mounting plate 10 30 electrically conductive component in the form of a conductor track of the detector 10 designed as a flat component 31 Support plate for component 30 32 heating segment, belongs to component 30 33 Wafer substrate, carries the carrier plate 31 34 electrical contact points 34 for the component 30 35 Protective layer on the component 30 38 heating segment of the compensator 11 43,44 Voltage sources 46 electrical contact for component 30 50 Hum Dependence of the measurement error Con meas - Con of the gain factor α in the test environment Cond Hum 50 P Dependence of the measurement error Con meas - Con of the gain factor α in the test environment Cond P 100 gas measuring device 100.1 additional gas measuring device 110 Calibration device, produces the models Mod and Mod.1, includes the humidity sensor 117 and the pressure sensor 118, includes the components 110.1 and 110.2 117 Humidity sensor of the calibration device 110 118 Pressure sensor of the calibration device 110 α Gain factor for the compensator voltage U11 in the total detection quantity Det α Hum Amplification factor for the humidity-optimized mode α Hum_P Gain factor for the humidity compensating mode α P Gain factor for pressure-optimized mode α P_Hum Gain factor for pressure compensating mode β Amplification factor for the signal U(ΔTemp) in the total detection quantity Det B spatial area to be monitored for the presence of a flammable target gas Con actual target gas concentration Con meas Target gas concentration derived from the gas measuring device 100 Cond Hum Test environment with an ambient humidity Hum of 90% relative humidity Cond P Test environment with an ambient pressure P increased by 200 mbar Cond Ref Reference test environment with an ambient humidity hum of 0% relative humidity and a target gas concentration con of 0% LEL Det Total detection size, depends on U10, U11 and U(ΔTemp), optionally additionally on U(Hum) and U(ΔP) Gp gas sample from area B Hum Ambient humidity, also humidity-optimized mode Hum_P humidity compensating mode I.1 Current flowing through detector 10 I.2 Current flowing through the compensator 11 Mod computer-evaluable model with functional relationships between the detection variables U10 and U11, the signal U(ΔTemp) and the target gas concentration Con meas , is applied by the evaluation unit 9 Mod. 1 computer-evaluable model, which uses the evaluation unit of the further gas measuring device 100.1, stored in the data memory 7.1 Ö1 Opening of the detector chamber 8 Ö2 Opening of the compensator chamber 5 P Ambient pressure, also pressure-optimized mode P_Hum pressure compensating mode ΔP Difference between the ambient pressure P and a given reference pressure, measured by the pressure sensor 18 Temp Ambient temperature ΔTemp Difference between the current ambient temperature Temp and a specified reference temperature, measured by the temperature sensor 14 U10 electrical voltage applied to detector 10 U11 electrical voltage applied to compensator 11 U(ΔTemp) signal supplied by the temperature sensor 14, correlated with the temperature difference ΔTemp x0 constant in the total detection quantity Det

Claims

[1] Gas measuring device (100), which is designed to measure the concentration of a combustible target gas (CH 4 ) in a spatial area (B), wherein the gas measuring device (100) - a detector (10), - a compensator (11), - a detector detection size sensor (12.1), - a compensator detection quantity sensor (12.2) and - a signal processing evaluation unit (9) includes, wherein the gas measuring device (100) is designed such that at least temporarily a gas sample (Gp) from the spatial area (B) reaches the detector (10) and the compensator (11), wherein the detector (10) has a detector detection quantity (U10) which is dependent on the concentration of the target gas (CH 4 ) in the gas sample (Gp), wherein the compensator (11) has a compensator detection quantity (U11) which - is influenced by at least one environmental condition acting on the gas sample (Gp) and - less than the detector detection size (U10) or even not at all correlated with the target gas concentration, wherein the detector detection quantity sensor (12.1) is designed to measure a measure of the detector detection quantity (U10), wherein the compensator detection quantity sensor (12.2) is designed to measure a measure of the compensator detection quantity (U11), wherein the evaluation unit (9) is designed to determine the concentration of the target gas (CH 4 ) in the gas sample (Gp), wherein the gas measuring device (100) is operable in a pressure-compensating mode or in a humidity-compensating mode during use, where in the pressure compensating mode the influence of the ambient pressure (P) is compensated in such a way that - the boundary condition is met that the influence of the ambient humidity (Hum) on the measurement result remains below a specified upper humidity influence limit, and - the influence of the ambient pressure (P) on a measurement result of the gas measuring device (100) is compensated as best as possible under this boundary condition, In the humidity compensating mode, the influence of the ambient humidity (Hum) is compensated in such a way that - the boundary condition is met that the influence of the ambient pressure (P) on the measurement result remains below a specified upper pressure influence limit, and - the influence of the ambient humidity (Hum) on the measurement result is compensated as best as possible under this boundary condition, and wherein the evaluation unit (9) is designed such that in the pressure-compensating mode the dependence of the determined target gas concentration on the detector detection variable (U10) and / or on the compensator detection variable (U11) is different than in the humidity-compensating mode. [2] Gas measuring device (100) according to claim 1, characterized by , that the gas measuring device (100) can additionally be operated in a pressure-optimized mode and / or in a humidity-optimized mode, wherein in the pressure-optimized mode the influence of the ambient pressure (P) on a measurement result of the gas measuring device (100) is compensated as best as possible without observing a boundary condition, In the humidity-optimized mode, the influence of the ambient humidity (Hum) on the measurement result is compensated as best as possible without observing a boundary condition and wherein the evaluation unit (9) is designed such that in each mode the dependence of the determined target gas concentration on the detector detection variable (U10) and / or on the compensator detection variable (U11) is different than in any other mode. [3] Gas measuring device (100) according to one of the preceding claims, characterized by , that the gas measuring device (100) can be operated either in pressure-compensating mode or in humidity-compensating mode and can optionally be operated in pressure-optimized mode or humidity-optimized mode. [4] Gas measuring device (100) according to claim 3, characterized by , that the gas measuring device (100) comprises a selection unit (16), wherein the selection unit (16) is designed to detect a specification of a user or a higher-level control, wherein the detected specification defines a mode in which the gas measuring device (100) is to be operated, wherein the gas measuring device (100) is designed to be operated in the pressure-compensating mode or in the humidity-compensating mode depending on an actuation of the selection unit (16), and wherein the gas measuring device (100) is optionally additionally designed to be operated in the pressure-optimized mode or in the humidity-optimized mode depending on an actuation of the selection unit (16). [5] Gas measuring device (100) according to claim 3 or claim 4, characterized by , that the gas measuring device (100) is designed to - to determine an estimate of the target gas concentration in the same gas sample (Gp) in at least two different modes and - to generate an alarm if at least one estimated value is outside a specified range of values ​​for the target gas concentration. [6] Gas measuring device (100) according to one of the preceding claims, characterized by , that the gas measuring device (100) additionally comprises at least one sensor (14, 17, 18) for an ambient condition, wherein the or each sensor (14, 17, 18) for an environmental condition is designed to measure a respective measure of the environmental condition, wherein preferably the or an additional sensor (14) is a temperature sensor, and wherein the evaluation unit (9) is designed to determine the concentration of the target gas (CH 4 ) in the gas sample (Gp) additionally depending on the respective signal of the or at least one sensor (14, 17, 18) for an ambient condition. [7] Gas measuring device (100) according to claim 6, characterized by , that the or at least one sensor for an environmental condition, in particular a sensor (17) for the ambient humidity or a sensor (18) for the ambient pressure, is optionally activated or deactivated, wherein the gas measuring device (100) is designed such that the evaluation unit (9) with the sensor (17, 18) activated, the concentration of the target gas (CH 4 ) in the gas sample (Gp) is additionally determined depending on the signal of the activated sensor (17, 18) and the gas measuring device (100) can be operated optionally in pressure-compensating mode or in humidity-compensating mode at least when the sensor (17, 18) is deactivated. [8] Gas measuring device (100) according to one of the preceding claims, characterized by , that the detector (10) comprises a heatable detector segment (20) and the compensator (11) comprises a heatable compensator segment (38), wherein the gas measuring device (100) is configured to heat the detector segment (20) such that the heated detector segment (20) detects combustible target gas (CH 4 ) in the gas sample (Gp) is oxidized and the oxidation further heats the detector segment (20), wherein the gas measuring device (100) is designed to heat the compensator segment (38), wherein the gas measuring device (100) - in a first alternative, is designed such that the heated compensator segment (38) oxidises less combustible target gas per unit of time than the heated detector segment (20) and in a second alternative, is designed so that a smaller amount of the gas sample reaches the compensator (11) than the detector (10) per unit of time, and wherein the detector detection quantity sensor (12.1) is designed to measure a measure (U10) for the temperature of the detector segment (20) as a detector detection quantity, and wherein the compensator detection variable sensor (12.2) is designed to measure a measure (U11) for the temperature of the compensator segment (38) as a compensator detection variable. [9] Gas measuring device (100) according to one of the preceding claims, characterized by , that the evaluation unit (9) has at least temporary read access to a computer-evaluable model (Mod), wherein the model (Mod) for the or each mode in which the gas measuring device (100) is operable comprises a functional relationship, where the functional relationship for a mode is a relationship between - the target gas concentration on the one hand and - the respective signal of each detection quantity sensor (12.1, 12.2) and optionally at least one signal from a sensor (14, 17, 18) for an environmental condition, on the other hand describes and wherein the evaluation unit (9) is designed to determine the target gas concentration the functional relationship for the mode in which the gas measuring device (100) is currently operated, to be applied to the respective signal of each detection quantity sensor (12.1, 12.2) and optionally to the respective signal of optional sensor (14, 17, 18) for an environmental condition. [10] Arrangement comprising - a first gas measuring device (100) according to one of the preceding claims and - a second gas measuring device (100.1) according to one of the preceding claims, wherein the evaluation unit (9) of the first gas measuring device (100) has at least temporary read access to a first computer-evaluable model (Mod) which describes a first dependence of the target gas concentration at least on the detector detection variable (U10) and on the compensator detection variable (U11) and optionally on at least one ambient condition for operation in the pressure-compensating mode, and wherein the evaluation unit (9.1) of the second gas measuring device (100.1) has at least temporary read access to a second computer-evaluable model (Mod.1) which describes a second dependence of the target gas concentration at least on the detector detection variable (U10) and on the compensator detection variable (U11) and optionally on at least one ambient condition for operation in the humidity-compensating mode. [11] Calibration device (110) for calibrating a gas measuring device (100) according to claim 9, wherein the calibration device (110) is designed to to detect a specification, wherein the detected specification specifies at least one mode in which the gas measuring device (100) is to be operable, to generate a computer-analyzable model (Mod) in such a way that the generated model (Mod) - includes a functional relationship for the or each mode detected and - can be used by the evaluation unit (9) of the gas measuring device (100), wherein the calibration device (110) is designed to use a predetermined sample and a set of predetermined possible functional relationships for generating the model, wherein the sample comprises at least one reference sample element, at least one pressure sample element and at least one humidity sample element, where each sample element - an identification of an ambient conditions-target gas combination, namely a combination of an ambient temperature, an ambient pressure, an ambient humidity and an actual target gas concentration and - a signal value combination, which has a value measured for the respective signal of each detection variable sensor (12.1, 12.2) at this ambient conditions-target gas combination, includes, wherein the calibration device (110) is designed to carry out the steps for each mode and for each sample element, - to apply each given possible functional relationship to the signal value combination of the sample element and thereby calculate a value for the target gas concentration and - to compare the calculated value for the target gas concentration with the actual value of the target gas combination in this sample element, and wherein the calibration device (110) is designed to, for each mode - to select a possible functional relationship using the comparison results and - to ensure that the selected functional relationship is used by the evaluation unit (9) as the functional relationship to be applied in this mode. [12] Gas measurement method for measuring the concentration of a combustible target gas (CH 4 ) in a spatial area (B) using a gas measuring device (100) which - a detector (10), - a compensator (11), - a detector detection size sensor (12.1) and - a compensator detection quantity sensor (12.2) includes, wherein the detector (10) has a detector detection quantity (U10) which is dependent on the concentration of the target gas (CH 4 ) in a gas sample (Gp), wherein the compensator (11) has a compensator detection quantity (U11) which - is influenced by at least one environmental condition acting on the gas sample (Gp) and - less than the detector detection size (U10) or even not at all correlated with the target gas concentration, wherein the gas measuring method comprises the steps of - causing a gas sample (Gp) from the area to reach the detector (10) and the compensator (11) at least temporarily, - the detector detection size sensor (12.1) measures a measure of the detector detection size (U10), - the compensator detection quantity sensor (12.2) measures a measure of the compensator detection quantity (U11) and - depending on the measured detector detection quantity (U10) and the measured compensator detection quantity (U11), the concentration of the target gas (CH 4 ) in the gas sample (Gp), wherein the gas measuring device (100) is operated in a pressure-compensating mode or in a humidity-compensating mode when carrying out the gas measuring method, In the pressure compensating mode, the influence of the ambient pressure (P) is compensated in such a way that - the boundary condition is met that the influence of the ambient humidity (Hum) on the measurement result remains below a specified upper humidity influence limit, and - the influence of the ambient pressure (P) on a measurement result of the gas measuring device (100) is compensated as best as possible under this boundary condition, and In the humidity compensating mode, the influence of the ambient humidity (Hum) is compensated in such a way that - the boundary condition is met that the influence of the ambient pressure (P) on the measurement result remains below a specified upper pressure influence limit, and - the influence of the ambient humidity (Hum) on the measurement result is compensated as best as possible under this boundary condition, and In the pressure-compensating mode, the dependence of the determined target gas concentration on the detector detection variable (U10) and / or on the compensator detection variable (U11) is different than in the humidity-compensating mode. [13] Calibration method for calibrating a gas measuring device (100) according to claim 9, where a sample and a set of given possible functional relationships are given, wherein the sample comprises at least one reference sample element, at least one pressure sample element and at least one humidity sample element, where each sample element - an identification of an ambient conditions-target gas combination, namely a combination of an ambient temperature, an ambient pressure, an ambient humidity and a target gas concentration and - a signal value combination, namely, for the respective signal of each detection variable sensor (12.1, 12.2), a value measured at this ambient conditions-target gas combination, optionally additionally at least one value of a sensor (14, 17, 18) for an environmental condition, includes, wherein the calibration method comprises the steps of - a specification is recorded, wherein the detected specification specifies at least one mode in which the gas measuring device (100) is to be operable, and - a computer-analyzable model (Mod) is generated in such a way, that the generated model (Mod) for the or each detected mode comprises a functional relationship and is applicable by the evaluation unit (9) of the gas measuring device (100), and wherein the calibration method comprises the steps that - for each mode and for each sample element, each given possible functional relationship is applied to the signal value combination of the sample element, thereby calculating a value for the target gas concentration and the calculated value for the target gas concentration is compared with the actual value of the target gas combination in this sample element, - for each mode, a possible functional relationship is selected using the comparison results and causing the selected functional relationship to be used by the evaluation unit (9) as the functional relationship to be applied in this mode.

Images