Device and method for detecting target gas by means of plurality of detector-compensator pairs

Abstract

The invention relates to a gas detection device (100) and a gas detection method, which are designed to detect the presence of a combustible target gas in a gas sample and / or to measure the concentration of a target gas in a gas sample. The detection device (DA) comprises at least two detectors (10.1,...) and at least one compensator (11). In this way, two different detector-compensator pairs (P.1,...) are formed. The compensators (11) belong to two different pairs. Each pair (P.1,...) can be turned on and off independently of each other pair. At each point in time, only one pair (P.1,...) is switched on. The heated detector (10.1,...) oxidizes the combustible target gas. A measuring unit measures a detection variable for each pair (P.1,...). The evaluation unit (9) derives the target gas concentration from the detected variable. In operation, each pair (P.1,...) is switched on in sequence, the respective detected variable is measured, and the pair is switched off again.

Description

Technical Field

[0001] The present invention relates to a gas detection device and a gas detection method, which are designed to detect the presence of at least one flammable target gas in a gas sample and / or determine the concentration of the target gas in the gas sample. Background Art

[0002] Gas detection devices comprising a detector and a compensator have become known. The detector and the compensator are heated by applying voltages respectively. The heated detector oxidizes the combustible target gas. A detection parameter related to the target gas concentration is measured. The heated compensator is able to oxidize the combustible target gas over a smaller range than the detector or even not oxidize the combustible target gas at all. Since the detector and the compensator ideally react to environmental conditions similarly, the compensator makes it possible to compensate for the influence of environmental conditions on the detection parameter. Such devices are also referred to as "thermal effect sensors". In order to sufficiently oxidize the target gas even at lower temperatures, the detector usually includes a catalytic material. Therefore, such devices are also referred to as "catalytic sensors". Summary of the invention

[0003] The object of the present invention is to provide a gas detection device and a gas detection method which, compared with known gas detection devices and gas detection methods each having a detector and a compensator, result in higher reliability at the same energy consumption and / or lower energy consumption at the same reliability.

[0004] This object is achieved by a gas detection device having the features of claim 1 and by a gas detection method having the features of claim 16. Where appropriate, advantageous embodiments of the gas detection device according to the invention are also advantageous embodiments of the gas detection method according to the invention and vice versa.

[0005] The gas detection device according to the invention is capable of determining the presence of at least one flammable target gas in a gas sample. Alternatively or additionally, the gas detection device is capable of determining the concentration of the target gas or at least one target gas in the gas sample. Optionally, the gas detection device is capable of determining the aggregate concentration of multiple target gases in the gas sample. The gas detection method according to the invention is performed using the gas detection device according to the invention.

[0006] The gas detection device according to the invention comprises a detection device. The detection device comprises at least three detection units. The term "detection unit" can denote a detector or a compensator. At least two different detection units of the detection device are detectors. At least one other detection unit is a compensator. At least two different detector-compensator pairs are thereby formed. Each detector-compensator pair respectively comprises exactly one detector and exactly one compensator and is sometimes referred to as a "pair" in short form.

[0007] According to the invention, the number of detectors is greater than the number of compensators. Thus, the compensator or at least one compensator belongs to at least two different detector-compensator pairs. It is possible that one compensator even belongs to at least three different detector-compensator pairs.

[0008] The gas detection device according to the invention is capable of switching each pair on, i.e. energizing each pair, and switching off again independently of each other pair. According to the invention, at each point in time during use, at most one detector-compensator pair is switched on. The other detector-compensator pairs or each other detector-compensator pair is switched off. It is possible that, in a stationary state of the gas detection device, each pair is switched off. It is also possible that the first pair is switched on in a first time period, then no pair is switched on in an intermediate time period, and then the second pair is switched on, wherein the second pair is different from the first pair or is the same pair as the first pair.

[0009] If a pair is switched on, a voltage is applied permanently or at least temporarily at the detector. In addition, a voltage is applied permanently or at least temporarily at the compensator. The term "temporarily" includes, in particular, a design in which the voltage is applied in a pulsating manner, which saves electrical energy compared to a design in which the voltage is applied permanently. The pulse frequency, pulse duration and / or duty cycle of the pulsating voltage applied at the detector may correspond to or differ from the pulse frequency, pulse duration and / or duty cycle of the voltage applied at the compensator.

[0010] Preferably, a pair is switched on in such a way that a voltage is applied to both the detector and the compensator, i.e. the pair is energized. The two voltages can have the same value or two different values. The voltage applied permanently or temporarily to the detection unit of the switched pair causes the detection unit to heat up.

[0011] The detection unit comprises a heating section. If a voltage is applied to the detection unit, a current flows and the heating section is heated. The detector differs from the compensator in that the heating of the detector leads to oxidation of the target gas - of course only if at least one oxidizable target gas is present in a sufficiently large concentration in the environment of the detector. Due to the oxidation, heat energy is released and further heats the detector. The heating of the compensator, however, leads to less oxidation than the heating of the detector. In one embodiment, the heating of the compensator does not lead to oxidation of the target gas at all.

[0012] Each detector unit and therefore each detector-compensator pair has a detection variable. The detection variable is related to the heat energy and therefore to the target gas concentration, which is released in the following way, that is, the detector oxidizes the combustible target gas. In one design, the detection parameter of the detection unit of a pair depends on the corresponding resistance or other electrical parameters of the two detection units. It is well known that the resistance of the conductive component depends on the temperature of the component in many cases. The corresponding temperature itself or the electrical power delivered respectively required to heat up the heating section can also be a detection parameter. Usually, all detector-compensator pairs have the same detection parameter, wherein for different pairs, the values ​​of these detection parameters can be different from each other or at least different from each other. If the detection unit of a pair oxidizes the target gas, the detection unit is further heated thereby, and the value of the detection parameter of the pair is changed thereby. An example: It is well known that the resistance of the conductive component increases with the temperature of the component. Another example: Since heat energy is released when oxidizing the combustible target gas, the greater the target gas concentration before oxidation, the less electrical power is needed to place the detector at a specific temperature.

[0013] The detection variable of the detector-compensator pair is influenced by the respective temperatures of the two detection cells. The oxidation of the target gas releases thermal energy. The thermal energy released and therefore the detection variable related to the thermal energy released is a measure of the concentration of the target gas.

[0014] The gas detection device according to the invention further comprises a measuring unit. The measuring unit can measure, for each connected detector-compensator pair, which value the detection variable currently assumes for the pair. For example, the measuring unit measures the corresponding voltages at the detector and at the compensator or the bridge voltage of a Wheatstone measuring bridge. The measuring unit preferably generates the time course of the detection variable for each pair.

[0015] The gas detection device according to the invention further comprises a signal processing evaluation unit, which receives the signal from the measuring unit and automatically evaluates the signal. Thus, for each switched pair, the evaluation unit receives at least one measured value that the detection variable takes for the pair, for example the value taken by the detector of the pair, and the measured value that the detection variable takes for the compensator of the pair, or the value taken by the optional bridge circuit of the pair. Using the value or at least one value for the pair, for example two values ​​for the detector and for the compensator, the evaluation unit automatically determines whether a target gas with a concentration above a predetermined lower detection limit is present and / or derives an estimate of the target gas concentration.

[0016] If, for example, a measure for a measured resistance is measured as a detection variable, then in many cases the greater the resistance of the detector, the greater the estimated value of the target gas concentration, and sometimes the smaller the resistance of the compensator, the greater the estimated value of the target gas concentration. In particular, the greater the difference between the two resistances, the greater the estimated value.

[0017] As already mentioned, each detector-compensator pair can be switched on and off independently of each other detector-compensator pair. In the case of a switched-on pair, a voltage is applied not only at the detector of the pair but also at the compensator, respectively, and preferably in a pulsating manner. In the case of a switched-off pair, a voltage is applied neither at the detector nor at the compensator, nor in a pulsating manner.

[0018] The gas detection device can perform the following steps for each pair:

[0019] - connect the pair,

[0020] - for the switched-on pair, the detection variable of the pair is measured, and the presence and / or concentration of the target gas is determined based on the measured detection variable, and

[0021] - Close the pair again.

[0022] Compared to a design in which two pairs are switched on at least sometimes simultaneously, the feature according to the invention that switches on at most one pair saves electrical energy.

[0023] Ambient conditions usually also influence the temperature of the connected detector, in particular the temperature, humidity and air pressure in the environment. Ideally, these ambient conditions act on the detector in the same way as on the compensator. Due to the compensator, the influence of the ambient conditions can be compensated to a certain extent by means of the detection variable for the compensator or for the adopted value of the pair by construction and / or calculation.

[0024] Substances, especially siloxanes and H2S, can precipitate on the surface of the detector. This "poisons" the detector. As a result, the detector is able to oxidize less combustible target gas and, at the same target gas concentration, the detector releases less and less heat as it becomes increasingly poisoned, and in extreme cases releases no heat at all. Because there are at least two detectors according to the invention, the service life of the gas detection device can be extended compared to a design with only one detector.

[0025] It is possible, but not necessary due to the present invention, to position a filter between the detection device and the spatial region to be monitored, wherein the filter reduces the inflow of harmful gases. Such filters often reduce the usability of the gas detection device, because the filter may reduce or even prohibit the inflow of some target gases, and the gas detection device is therefore unable to detect these target gases. In addition, the filter may become clogged and may cause the gas sample to pass more slowly or even not at all.

[0026] Typically, the or each compensator is less poisoned than each detector. The main reason for this is that the compensator oxidizes less target gas than the detector and is therefore less poisoned by deposits. It is therefore particularly advantageous to have the feature according to the invention that the same compensator of the gas detection device according to the invention is a component of at least two different pairs. Compared to a gas detection device with a plurality of detectors and exactly as many compensators as detectors, the gas detection device according to the invention requires fewer detection units and generally also less electrical energy.

[0027] In some cases, even if each detector is strongly poisoned, a target gas with a sufficiently high concentration can still be found. In one design, the value adopted by the detection variable of the measuring compensator is also measured. Many target gases have a greater thermal conductivity than air, so that even if the detector is completely poisoned, the compensator is cooled by the target gas, which changes the detection variable of the compensator and thereby changes the detection variable or detection variables of the pair. However, the effect caused by the reduced thermal conductivity is much smaller than the effect on the detector of the heat energy released due to the oxidation of the target gas.

[0028] According to the invention, there are more detectors than compensators. This feature has the following advantages, among others:

[0029] As already explained, each detector is generally poisoned more quickly than the or each compensator, and in particular because deposits form on the detectors due to oxidation. Therefore, in many cases, this design solution leads to a longer service life and / or lower energy consumption than a gas detection device with exactly as many compensators as detectors.

[0030] It is possible that the detection unit is a flat component, in particular mounted on a circuit board. In many cases, the more area the component takes up on the circuit board, the greater the manufacturing costs. Compared to a gas detection device comprising exactly as many compensators as detectors and comprising exactly as many detectors as the gas detection device according to the invention, the feature according to the invention of having fewer compensators than detectors saves space and therefore generally saves manufacturing costs.

[0031] The embodiment of the invention provides for different possibilities for in which order and with what frequency the components are switched on and off.

[0032] In one design, the detector-compensator pairs are switched on and off during the use period so that, overall, i.e., measured across the entire use period, all pairs are switched on for the same length of time and switched off for the same length of time. In another design, the first detector-compensator pair is switched on for a longer duration than the second detector-compensator pair overall. In an improvement or modification, the first pair is switched on N1 times during the use period and the second pair is switched on N2 times. N1 and N2 are two numbers, N2 is at least 1, preferably at least 2, and N1 is greater than N2. Preferably, the same time interval passes each time between the time point at which a pair is switched on and the time point at which the pair is switched off again. Therefore, the pair is always switched on within the same activation time interval. However, different activation time intervals are also possible for one pair or for two different pairs.

[0033] In one implementation, the gas detection device performs a sequence at least once during the use period, the sequence comprising the following steps: firstly the first detector-compensator pair is switched on and off again N times, while the second detector-compensator pair remains continuously switched off. The second pair is then switched on and off again once. In this case, N is a number greater than 1. The first pair is therefore usually more strongly loaded than the second pair.

[0034] In many cases, these designs lead to the detectors of the second pair being poisoned more slowly than the detectors of the first pair. If the detectors of the first pair are poisoned so strongly that they are no longer sufficiently reliably oxidized, in many cases the target gas can still be detected with the detectors of the second pair. As already explained, the same compensator can belong both to the first pair and to the second pair.

[0035] A number of designs have been described further above, in which the first pair is switched on longer than the second pair. As a result, the first pair is more strongly loaded than the second pair and at least its detectors are poisoned more strongly than the detectors of the second pair in many cases. Both pairs preferably provide target gas concentration estimates, respectively. Typically, the target gas concentration does not change significantly between an activation time interval of the first pair and a subsequent activation time interval of the second pair.

[0036] In one embodiment, the evaluation unit can compare the two target gas concentration estimates from two pairs with each other. If the two estimates differ from each other by more than a limit, this is a sign that a pair is defective. In response, the evaluation unit (optionally after verification) triggers one of the following two steps:

[0037] - In addition, the corresponding detection variable values ​​of the two pairs are used. However, the value of the parameter is automatically changed. The evaluation unit uses this parameter value in order to determine the presence of the target gas and / or measure the target gas concentration and derive a target gas concentration estimate based on the measured detection variable values ​​of the first pair.

[0038] - The first pair is disconnected and not connected again before inspection or replacement.

[0039] This design makes it possible for the gas detection device itself to be automatically checked with relatively high reliability. If the two target gas concentration estimates of the two pairs deviate from each other by more than a limit, this is a sign that the detector is relatively strongly poisoned. In many cases, the rationality check can automatically ascertain whether the deviation between the two estimates is caused by poisoning of the detector or by other errors, such as interrupted electrical contact. Since, according to this design, the detectors of the first pair are switched on for a longer time than the detectors of the second pair, the detectors of the first pair are usually poisoned detectors, while the detectors of the second pair are not poisoned detectors. Other errors may of course involve the first pair or the second pair.

[0040] In one embodiment, at least one pair has a detection variable that is influenced not only by the temperature of the detector but also by the temperature of the compensator. This applies, for example, if a bridge circuit is used. In another embodiment, at least one pair has two different detection variables, namely a detection variable of the detector and a detection variable of the compensator. The two detection variables can be varied independently of one another in time. The measuring unit can measure both detection variables.

[0041] In one embodiment, when a pair is switched on, a voltage is continuously applied not only at the detector but also at the compensator, preferably a pulsating voltage. In a different embodiment, when a pair is switched on, a voltage is only temporarily applied at the detector and only temporarily applied at the compensator. If a voltage is applied at the detector, the detection variable of the detector is measured. If a voltage is applied at the compensator, the detection variable of the compensator is measured. The two measured values ​​of the two detection variables are then compared with each other in order to determine the presence of the target gas and / or determine the target gas concentration. In some cases, this design loads the detector less and / or saves electrical energy compared to a design in which a voltage is applied not only at the detector but also in the compensator at least temporarily at the same time.

[0042] In a refinement of this design, even when the pair is switched on, at a point in time the voltage is applied only to one of the two detection units, either to the detector or to the compensator, but not to both detection units. Even in this refinement, the voltage can be applied in a pulsating manner. This design saves electrical energy.

[0043] According to the invention, one pair is switched on in an activation time interval and the other pair or each other pair is switched off in the activation time interval. In one implementation of the design just described, in the activation time interval, the voltage is applied for a shorter time at the compensator than at the detector. Particularly preferably, the measuring unit measures the detection variable for the compensator only once in the activation time interval, but measures the detection variable for the detector twice. This implementation saves even more electrical energy and takes into account the following scenario: the compensator is essentially affected by environmental conditions, and these environmental conditions usually change only slowly, while the target gas concentration and thus the detection variable of the detector can change more quickly.

[0044] The detection device preferably extends in a plane. According to the preferred design, the maximum size of the detection device perpendicular to the plane is at most 20% of the maximum range in the plane. The vertical range is particularly preferably at most 10%, especially at most 5%. For example, the circuit board extends in the plane and the detection unit is arranged on and / or in the circuit board. In the viewing direction perpendicular to the plane, the detection units are arranged without overlapping, preferably in at least one row, optionally in a rectangular arrangement with at least two rows. The compensator or each compensator is preferably arranged between two detectors respectively. In a design, the detection unit is arranged in a rectangular arrangement with K rows and L columns, wherein K>=3 and L>=3 are applicable and wherein the compensator or each compensator is arranged inside the rectangle. It is also possible that the detection unit is distributed on at least two circuit boards. The two circuit boards can extend in the same plane or in two different planes, wherein the two different planes are preferably parallel to each other. The gas sample preferably flows around the two circuit boards.

[0045] Compared to, for example, spherical components (thermistors), this flat construction reduces the thermal mass of the detector and the compensator. As a result, the detection unit reaches the respectively desired operating temperature more quickly. This in turn enables these pairs to be switched on for a shorter period of time, for example with shorter pulses and / or longer intervals between individual pulses and / or a smaller duty cycle. This in turn reduces the consumption of electrical energy, which is desirable in particular in the case of devices with their own voltage supply. Alternatively, a higher sampling rate can be achieved at the same energy consumption. In addition, this design solution generally saves installation space and / or weight.

[0046] In many cases, the flat design just described in combination with a pulsating voltage and shorter pulses leads to a longer service life of the detector, compared to designs in which the voltage is permanently applied to the switched-on detector or the pulses have to be longer in order to sufficiently heat, for example, a spherical component, because the detector is less susceptible to poisoning. The detector arrangement is also generally easier to produce than a detector arrangement with, for example, a spherical detector cell. This applies in particular in highly automated production.

[0047] In one design, all detection units are arranged in the same plane. Since the detection units are arranged in this plane without overlap, the gas sample to be checked for the target gas or a target gas reaches all detection units relatively quickly. If two detection units would overlap, in many cases it would take more time until the target gas reaches all detection units. As a result, the detection device would require more time until it provides reliable measurement results. In addition, in some cases, the flow of gas to the detection units would become difficult, which could lead to erroneous measurement results.

[0048] According to the invention, the detection device comprises two detector-compensator pairs. In a preferred embodiment, the detection device additionally comprises a third detector-compensator pair, which also comprises exactly one detector and exactly one compensator. In general, the detection device according to this embodiment comprises at least three detectors and at least one compensator.

[0049] The first detector-compensator pair provides a first target gas concentration estimate. The second pair provides a second target gas concentration estimate. The evaluation unit can compare the two estimates with one another. If the two estimates do not differ from one another by more than a predefined limit, the third pair preferably remains switched off. How large this limit is can depend on which time has passed between a state in which the first pair is switched on and the second pair is switched off and a state in which the second pair is switched on and the first pair is switched off. If the two estimates differ from one another by more than this limit, the gas detection device causes the third pair to be switched on.

[0050] Therefore, as long as the two estimated values ​​of the first pair and the second pair do not differ from each other by more than a limit, the third pair is reserved and is not switched on and is therefore not used. Therefore, the third pair is also not poisoned for a long time. When the difference is below this limit, not only the first pair but also the second pair are intact. As long as the third pair remains switched off, the third pair is not poisoned. If the two estimated values ​​deviate from each other by more than a limit, this is a strong poisoning of the detector that is more strongly loaded in the first pair and / or the second pair. In this case, the third pair is used at least temporarily. In many cases, it can be determined based on the measured value of the detection parameter of the third pair: whether the detection parameter value of the first pair or the detection parameter value of the second pair is correct, and therefore the pair that provides a possibly incorrect detection parameter value must be switched off and / or checked. For example, the first pair and / or the second pair can be checked or even readjusted / calibrated.

[0051] Each detector of the at least three pairs has an active surface. The active surface is in contact with the gas sample. The detector can oxidize a target gas in the gas sample by means of the active surface - of course only when the gas sample includes at least one oxidizable target gas. Preferably, the detectors of the third pair have a larger active surface than the detectors of the first pair and the detectors of the second pair. In many cases, the detectors of the third pair can thus provide measurement values ​​with particularly great reliability.

[0052] In one embodiment, a zero value is predefined for each detector-compensator pair. For example, the zero value is specified or determined in a previous calibration. If no target gas is present in the environment of the pair, the detection variable of the pair does not adopt this zero value. In many cases, the detection variable of the pair does not adopt the value zero even if no target gas is present in the environment. In other words: the zero value is usually not equal to zero. Common reasons are as follows: the zero values ​​of the detectors and compensators of the pair differ from each other, in particular due to construction-related and / or manufacturing-related differences. Due to the zero value, these differences do not need to be reset to zero in advance.

[0053] The connected detector-compensator pairs provide the measured value of the detection variable. The evaluation unit preferably uses the difference between the measured value and a predetermined, for example stored, zero value of the pair as the detection variable value. The evaluation unit determines the presence of the target gas and / or measures the target gas concentration based on the difference. In one embodiment, the evaluation unit can calculate the difference between the value currently assumed by the detection variable and the zero value of the detection variable for each detection unit. Thus, there are two differences for each connected pair. It is also possible to predetermine the zero value for the bridge circuit.

[0054] This design with zero value saves the necessity of realizing and manufacturing the detection units in a structurally identical manner so that the detection variable of each detection unit assumes the same value in the absence of target gas and under the same ambient conditions. On the contrary, the zero value compensates for the differences caused by the structural method to a certain extent.

[0055] In one embodiment, the gas detection device comprises a housing, which at least accommodates the detection device and the measuring unit, and optionally its own voltage supply unit. The evaluation unit can also be located in the housing. It is also possible that the evaluation unit is spatially remote from the housing and is connected to the measuring unit via a data connection, in particular via a data connection via radio waves or via a cable. This design saves the necessity of arranging the evaluation unit in the housing. It is possible that the same evaluation unit can be connected to different gas detection devices.

[0056] In one embodiment, the gas detection device comprises a dedicated voltage supply unit. In another embodiment, the gas detection device can be connected to a fixed voltage supply network.

[0057] In one embodiment, the gas detection device comprises an output unit, which outputs the measurement result in at least one human-perceptible form, in particular visually, acoustically and / or tactilely (via vibration). In another embodiment, the gas detection device comprises a communication unit, which is capable of transmitting a message with the measurement result to a spatially remote receiver. These two embodiments can be combined with one another. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention will be described below based on embodiments. In this case,

[0059] Figure 1 A gas detection device is shown with a detector and a compensator, both of which are designed as thermistors, wherein a bridge voltage is measured;

[0060] Figure 2 A flat detection unit is shown in a perspective view;

[0061] Figure 3 Shown in top view Figure 2 Detection unit;

[0062] Figure 4 A gas detection device is shown having a detector designed as a thermistor and a flat compensator, wherein both the detector voltage and the compensator voltage are measured;

[0063] Figure 5 A top view of a gas detection device according to the present invention on a circuit board is shown, the gas detection device having nine detectors and one compensator, i.e. eight pairs;

[0064] Figure 6 shows an exemplary time course of a self-test of a gas detection device after a steep rise in target gas concentration is detected, wherein all pairs are intact;

[0065] Figure 7 Show Figure 6 modification of the time-varying process, where one of the pairs is defective;

[0066] Figure 8 shows an exemplary time course of a self-test of a gas detection device after a steep drop in target gas concentration is detected, wherein all pairs are intact;

[0067] Fig. 9 Show Figure 8 The change process is modified, and one of the pairs is defective. DETAILED DESCRIPTION

[0069] The gas detection device according to the invention is used to detect at least one combustible gas and / or to determine the concentration of a combustible gas. In the following, the combustible gas is referred to as a "target gas". In one embodiment, if there are multiple target gases, the sum of the target gas concentrations is determined.

[0070] In one application, the gas detection device is used to monitor a spatial region and in this case detect at least one flammable target gas and / or determine the target gas concentration or ensure that no flammable target gas is present above a detection limit. The spatial region is, for example, a refinery or other production facility, the interior of a building, a mine, the interior of a vehicle or the interior of an aircraft. The flammable gas is, for example, methane (CH4).

[0071] In another application, the gas detection device is used to check the subject for substances that can be determined in the exhaled air, in particular alcohol. It is well known that the air exhaled by the subject contains breath alcohol, provided that the subject has consumed alcohol and this alcohol has not been completely broken down in his body. In this case, the alcohol is still present in the subject's blood and / or in his lungs and in his mouth. In the case of this application, the subject inputs a breath sample into the mouthpiece of the gas detection device. At least a portion of the emitted breath sample reaches the interior of the gas detection device. In the case of this application, the gaseous breath alcohol is a flammable target gas.

[0072] In one implementation, the gas detection device is a portable device that a person can hold in their hand or can also fasten to their clothing or protective gear. For example, the user carries such a gas detection device when the user stays in an area where at least one flammable target gas may be present. Or the gas detection device is held in front of the subject's mouth so that the subject can input a breath sample.

[0073] Preferably, in the case of the first application, and optionally also in the case of the second application, the gas detection device generates an alarm in at least one form perceptible to a person when a target gas concentration above a predetermined limit occurs. For example, the alarm is output visually, acoustically and / or tactilely (by vibration). In the case of these applications, the gas detection device comprises its own voltage supply unit.

[0074] Figure 1 A gas detection device 100 as known from the prior art is shown by way of example. Figure 1 The described principle can also be applied to the gas detection device according to the invention. This principle is already known under the names "thermal effect sensor" and "catalytic sensor".

[0075] exist Figure 1 In the embodiment shown in the figure, an outer housing 4, for example made of hard plastic, surrounds a heat-resistant cylindrical inner housing 1, for example made of steel. A gas sample can enter the interior of the inner housing 1 through an opening O with a flameproof device 2, for example by sucking a gas sample or by diffusion.

[0076] The gas detection device 100 comprises a detector 10.p and a compensator 11.p. The general term "detection unit" is used for the detector and the compensator in the following. That component of the gas detection device 100 which comprises the detector or each detector and the compensator or each compensator and the electrical contacts is referred to as the "detection arrangement" DA. The detection arrangement DA is preferably located completely inside the inner housing 1.

[0077] The detector 10.p comprises a conductive member having a heating section 20 and two electrical contacts 36, wherein the two electrical contacts 36 are mounted on a plate 22. In the embodiment shown, the heating section 20 has the shape of a spiral wire and is preferably made of a material that ideally does not chemically react with the target gas to be detected, i.e. is inert. The ceramic cover 21 surrounds the heating section 20 and has the shape of a solid sphere in the example shown. A catalytic coating is applied to the outer surface of the ceramic cover 21, which is indicated by a circle 23. As a catalytic material, platinum or palladium or other suitable metals or other alloys are suitable, for example. The ceramic cover 21 is preferably porous so that the gas sample can also reach the interior of the ceramic cover 21.

[0078] If voltage is applied to the electrical contact 36, current flows through the heating section 20 and the heating section 20 heats up. The heated heating section 20 oxidizes the combustible target gas in the interior of the inner housing 1 and oxidizes it in cooperation with the catalytic material 23 in the ceramic cover 21. It is shown by way of example that during oxidation, methane is converted into carbon dioxide and water, i.e., a chemical reaction occurs.

[0079] CH4+2O22H2O+C02

[0080] During this chemical reaction, heat energy is released. This released heat energy further heats the temperature of the heating section 20. Therefore, the temperature of the heating section 20 is a measure of the concentration of the target gas in the interior of the housing 1.

[0081] A measure of the temperature of the heating section 20 is measured. In one design, the resistance of the heating section 20 is measured. As is known, in the case of many conductive materials, the resistance changes with temperature. Generally speaking, the higher the temperature, the greater the resistance.

[0082] However, the temperature of the heating section 20 is affected not only by the target gas concentration, but also by the environmental conditions, in particular by the ambient temperature and / or the temperature of the gas sample in the interior of the internal shell 1. Therefore, a compensator 11.p is additionally arranged in the interior of the shell 1. The compensator 11.p also includes a heating section and a ceramic covering, but does not include a catalytic coating in this embodiment, but includes a smaller catalytic coating in another possible implementation. Therefore, the compensator 11.p cannot oxidize the combustible target gas at all or at least does so more slowly or less. Ideally, the environmental conditions act on the compensator 11.p in exactly the same way as on the detector 10.p. Therefore, the compensator 11.p makes it possible to compensate for the influence of environmental conditions on the detector 10.p in a certain degree in calculation.

[0083] In accordance with Figure 1 In the implementation mode, the gas detection device 100 additionally includes the following components:

[0084] a voltage supply unit 42, for example a set of rechargeable batteries (accumulators),

[0085] - a resistor R20 connected in parallel with the detector 10.p,

[0086] - a resistor R21 connected in parallel with the compensator 11.p,

[0087] - Electric line 3,

[0088] - Voltage sensor 40 and

[0089] - Current intensity sensor 41 .

[0090] exist Figure 1 The following electrical characteristic variables are also shown:

[0091] - Resistor R10 of detector 10.p,

[0092] - Resistor R11 of compensator 11.p,

[0093] - voltage U42 at the voltage supply unit 42,

[0094] - the intensity I3 of the current flowing through the electrical line 3,

[0095] - a voltage U10 applied to the detector 10.p, and

[0096] - Voltage U11 applied to the compensator 11.p.

[0097] Note: The term "resistance" refers to a component on the one hand and an electrical property of a component on the other hand.

[0098] In accordance with Figure 1In an embodiment of the detection device, the two detection units form a Wheatstone measuring bridge. The detector 10.p and the compensator 11.p are connected in series. The resistance of the voltage sensor 40 is high compared to the resistance of the components 10.p, 11.p, R20 and R21. In one embodiment, the voltage sensor 40 directly measures the so-called bridge voltage ΔU=(U10-U11) / 2. The current intensity sensor 41 measures the current intensity I3.

[0099] Ideally, when there is no flammable target gas in the interior of the housing 1, the bridge voltage ΔU is equal to zero. However, due to differences caused by the construction method, in particular, the bridge voltage ΔU is usually not equal to zero even if there is no flammable target gas. Therefore, the so-called zero point ΔU,0 is determined in advance, preferably empirically. The zero point ΔU,0 is the bridge voltage ΔU in the case where no flammable target gas occurs.

[0100] The measured detection variable is related to the concentration of the combustible target gas. Figure 1 An evaluation unit (not shown) which processes the signals applies a predetermined functional relationship to the detection variable ΔU-ΔU,0 and derives an estimated value for the target gas concentration.

[0101] In one implementation, the current intensity I3 is kept constant by closed-loop control. The voltage ΔU is then related to the resistance and thus to the temperature change caused by the oxidation of the target gas. The difference ΔU-ΔU,0 serves as the detection variable.

[0102] Figure 2 Another implementation of the detector and the compensator is shown in a perspective view. The detector according to this implementation is denoted by 10.m and the compensator is denoted by 11.m. Figure 3 Shown in top view Figure 2 The detector 10.m and the compensator 11.m are used in conjunction with Figure 1 The detector 10.p has the same principle, but is Figure 1 The detector of is much flatter. This correspondence applies to the compensator 11.m.

[0103] The detector 10.m and the compensator 11.m respectively include the following components:

[0104] an electrically conductive component 30 having a heating section 32 and an electrical contact 46, wherein the component 30 has the shape of a conductor track,

[0105] - a protective layer 35,

[0106] - a carrier plate 31 extending in a plane, wherein the plane is inclined to Figure 2 of the drawing plane and is located in Figure 3 In the drawing plane,

[0107] - a wafer substrate 33 carrying a carrier plate 31, and

[0108] An electrical contact point 34 for the electrically conductive component 30 .

[0109] 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 the gas sample. In one embodiment, the protective layer 35 is made of silicon nitride. In the case of the detector 10.m, the catalytically active material is applied to the protective layer 35, and at least in the region 24 above the heating section 32.

[0110] The compensator 11.m comprises the same components as the detector 10.m. Preferably, the compensator 11.m differs from the detector 10.m in that less catalytic material participates in the protective layer 35 of the compensator 11.m or the catalytic material does not participate in the protective layer 35 of the compensator 11.m at all, so that the catalyst 11.m is not able to oxidize the combustible target gas or is able to do so to a lesser extent than the detector 10.m.

[0111] The conductor track 30 may be formed by Figure 1 The conductor track 30 is preferably made of the same conductive material as the component 20 of the detector 10.p. The heating section 32 of the conductor track 30 is preferably realized in such a way that the conductor track 30 is bent or wavy in a zigzag shape or in another way in the region 24. Alternatively, the conductor track 30 has a cross section that varies over the length of the conductor track 30, so that a sufficiently high operating temperature is achieved when a current flows through the conductor track 30. Preferably, the maximum dimension of the conductor track 30 and thus the maximum dimension of the heating section 32 in the plane of the carrier plate 31 is less than 2 mm, particularly preferably less than 1 mm, and particularly preferably between 0.1 mm and 0.5 mm. The heating section 32 or the entire conductor track 30 is also made of metal, for example of platinum or wolframite or tungsten or titanium, or of an alloy comprising at least one of the aforementioned metals.

[0112] The carrier plate 31 preferably has a thickness of less than 10 μm, particularly preferably less than 2 μm, in particular a thickness of at most 1 μm, and is preferably made of a material containing silicon, for example a glass-like material. In this embodiment, the carrier plate 31 is fastened to the wafer substrate 33 by means of four tabs. During production, a fixture can clamp and mount the compensator 11.1 on the wafer substrate 33.

[0113] The conductive track 30 is applied to the surface of the carrier plate 31 and is preferably embedded in the carrier plate. The conductor track 30 preferably has a maximum thickness of at most 1 μm, particularly preferably at most 0.5 μm, i.e. a maximum dimension perpendicular to the plane of the carrier plate 31. The carrier plate 31 thermally decouples the conductor track 30 from the environment and preferably also electrically decouples it from the environment. The carrier plate 31 is in contact with the surrounding air on at least one side, which results in good thermal insulation of the conductor track 30. The carrier plate 31 can contain recesses 15.1, .... The recesses 15.1, ... can lead to the strip-shaped carrier plate 31. The carrier plate 31 can also be constructed over the entire surface.

[0114] In one embodiment, the wafer substrate 33 is less than 1 mm, particularly preferably less than 0.4 mm thick, and has a maximum diameter of several millimeters. The carrier plate 31 is applied to the wafer substrate 33, for example by chemical vapor deposition or by evaporation. Preferably, a recess is embedded in that region of the wafer substrate 33 which is located below the heating section 32, so that the heating section 32 is surrounded by air on both sides. This improves thermal insulation. For example, the recess is produced by etching it into the material.

[0115] On the carrier plate 31, an electrical connection 46 connects the heating section 32 to the electrical contact point 34. The protective layer 35 electrically insulates the conductor track 30 and thus the heating section 32 from the environment and reduces the risk of damage. In particular, the protective layer 35 prevents the conductor track 30 from coming into contact with gases from the environment, in particular gases that may be harmful to the conductor track 30, such as hydrogen.

[0116] Figure 4 A design is schematically shown, in which the detector is arranged according to Figure 1 The detector 10.p in is designed, and the compensator is designed according to Figure 2 and Figure 3 The compensator 11.m in is designed.

[0117] Figure 4 The gas detection device 100 includes the following components:

[0118] a detector 10 . p having a heating section 20 , a ceramic covering 21 and a coating 23 made of a catalytic material,

[0119] a compensator 11 . m having a heating section 32 and a carrier plate 31 and optionally also a catalytic material,

[0120] - a voltage source 42,

[0121] - Two switches 7.10 and 7.11,

[0122] a controllable voltage actuator 8 . 10 which is able to vary the voltage U10 applied at the detector 10 . p ,

[0123] a controllable voltage actuator 8.11, which is able to vary the voltage U11 applied at the compensator 11.m,

[0124] - two voltage sensors 40.10 and 40.11,

[0125] - two current intensity sensors 41.10 and 41.11,

[0126] - Resistors R20 and R21, see Figure 1 ,

[0127] a schematically shown control device 6 for processing signals with an evaluation unit 9,

[0128] - an optional thermal barrier 17 between the detector 10.p and the compensator 11.m,

[0129] - With opening The outer shell 4 and

[0130] - A stable inner casing 1.

[0131] according to Figure 4 The design scheme can also be used according to Figure 2 and Figure 3 It is also possible that the compensator 11 is implemented according to the detector 10.m of the embodiment of the present invention. Figure 1 The compensator 11.p is designed.

[0132] Furthermore, the spatial region B to be monitored is indicated, as well as arrows which illustrate how a gas sample from the region B flows through the opening O into the interior of the housing 1 . The fire protection device 2 is not shown.

[0133] The voltage sensor 40.10 measures the voltage U10 applied at the detector 10.p, and the voltage sensor 40.11 measures the voltage U11 applied at the compensator 11.m. Figure 1 Compared to the design of FIG. 1 , two currents of different current intensities can flow through the detector 10 .p and the compensator 11 .m. The two current intensity sensors 41 . 10 and 41 . 11 measure the two current intensities I10 and I11 .

[0134] The two current intensities I10 and I11 are preferably kept constant by closed-loop control, respectively. The temperature of the heating section 20 of the detector 10.p is related to the resistance, and at a constant current intensity I10, the resistance is related to the voltage U10. Correspondingly, the temperature and resistance of the heating section 32 of the compensator 11.m are related to the voltage U11. Preferably, two zero values ​​of the voltage are predetermined in the absence of a combustible target gas, i.e., the zero value U10.0 of the voltage U10 at the detector 10.p and the zero value U11.0 of the voltage U11 at the compensator 11.m. Preferably, the difference (U10-U10.0)-(U11-U11.0) is used as the detection variable.

[0135] In order to save electrical energy, in this embodiment, the control device 6 causes that the voltage is not permanently applied at the detector 10.p and the compensator 11.m, but a pulsating voltage is applied. The control device 6 controls the two switches 7.10 and 7.11 with the purpose of pulsating the voltage U10 or U11 applied at the detector 10.p or the compensator 11.m. Preferably, the pulse rate and / or pulse duration of the voltage U10 applied at the detector 10.p can be set and changed independently of the pulse rate and pulse duration of the voltage U11 applied at the compensator 11.m.

[0136] Figure 5 The gas detection device 100 according to the invention is schematically shown in a top view, wherein nine detection units, namely eight detectors 10.1, ..., 10.8 and a compensator 11, are applied to a circuit board designed as a circuit board and on a Figure 5 The control device 9 is also applied to the carrier plate 31 extending in the drawing plane of FIG. Each detector 10.1, ..., 10.8 and the compensator 11 are preferably as described with reference to FIG. Figure 2 and Figure 3 It is also possible that at least one detector 10.1, ..., 10.8 or compensator 11 is constructed as described, that is, as a flat component. Figure 1 The carrier plate 31 provides electrical contacts for the nine detection units 10.1, ..., 10.8, 11, wherein these electrical contacts are Figure 5 The nine detection units 10.1, ..., 10.8, 11 and the circuit board 31 belong to the detection device DA.

[0137] exist Figure 5As seen in the observation direction, the nine detection units 10.1, ..., 10.8, 11 are arranged side by side on the carrier 31 without overlapping, and a distance appears between two adjacent detection units. Therefore, the gas sample can reach all nine detector units at the same time without one detector unit shielding another detector unit, i.e., limiting the process of the gas sample reaching another detector unit. In the illustrated implementation, the nine detector units 10.1, ..., 10.8, 11 form a 3×3 matrix, i.e., an arrangement of three rows and three columns with three detector units each, wherein a single compensator 11 is arranged in the middle. Since the compensator 11 is arranged in the middle, only a relatively small distance appears between the compensator 11 and each detector 10.1, ..., 10.8, so that the environmental conditions around the compensator 11 and around the detectors 10.1, ..., 10.8 are almost the same.

[0138] Of course, other numbers of rows and / or columns of circuit boards with detector units and other numbers of detector units per row and / or per row are also possible. The compensator 11 is preferably, but not necessarily, arranged in the center. The gas detection device 100 can also include a plurality of such circuit boards with detector units, wherein these circuit boards are preferably arranged parallel to each other and the gas sample can reach each circuit board.

[0139] It is possible that all nine detector units 10.1, ..., 10.8, 11 have the same active surface, wherein the active surface is in contact with the gas sample arranged in the interior of the housing 1. In the example shown, however, eight detector units 10.1, ..., 10.7, 11 each have the same active surface. Compared to the detectors 10.1 to 10.7 and compared to the compensator 11, the detector 10.8 has a larger active surface, preferably an active surface that is at least half as large, particularly preferably an active surface that is twice as large.

[0140] In the embodiment shown, eight detector-compensator pairs P.1, ..., P.8 are implemented on a carrier plate 31, wherein the detector-compensator pair Px comprises a detector 10.x and a compensator 11 (x=1, ..., 8). Therefore, a single compensator 11 belongs to each of the eight detector-compensator pairs P.1, ..., P.8. In general, the gas detection device 100 according to the invention comprises m detectors and n compensators, wherein m>n>=1 and m>1 applies. Preferably even m>=2*n, particularly preferably m>=5*n applies. In the case of m detectors and n compensators, up to m*n pairs are formed in total, each of which has one detector and one compensator. The advantages of the preferred design scheme in which there are more detectors than compensators are as follows: deposits are often formed on the heated surface of the detector. The detector is poisoned during use. In general, much fewer deposits are formed on the heated surface of the compensator. If there are more detectors than compensators, in many cases, the gas detection device can be operated for a longer time even if individual detectors fail.

[0141] Figure 5 The control device 9 schematically shown in the figure is capable of switching each detector-compensator pair Px on and off independently of each other detector-compensator pair Py(y#x). The control device 9 causes that at each point in time at most one pair Px is switched on and supplied with voltage permanently or in a pulsating manner, while all other pairs Py are switched off. If the detector-compensator pair Px is switched on, a voltage is applied not only at the detector 10.x but also at the compensator 11, respectively, preferably a pulsating voltage, and a current flows not only through the heating section of the detector 10.x but also through the heating section of the compensator 11. The detector 10.a and the compensator 11 can in particular be connected as follows Figure 1 or connected in parallel with each other, as shown in Figure 4 Preferably, in the case of the switched pair Px, the voltage is applied in a pulsed manner at the detector 10.a and at the compensator 11 in order to save energy.

[0142] According to the invention, the gas detection device 100 is operated such that during use, most of the time exactly one pair Px is switched on and the remaining pairs are switched off. "Most of the time" means that between the activation time interval of one pair Px and the subsequent activation time interval of another pair Py an intermediate time period elapses, in which all pairs are switched off, wherein the intermediate time period is preferably shorter than the activation time interval or each activation time interval. During rest periods, all pairs are usually switched off. The switched on pairs Px provide values ​​of the detection parameters, such as the values ​​of the bridge voltage (according to Figure 1 design scheme) or provide the value of the detector voltage and the value of the compensator voltage respectively (according to Figure 4 The value of the detection variable is a measure of the current target gas configuration. It is of course possible that different pairs successively provide different values ​​for the target gas concentration, even if the target gas concentration remains the same. In addition to differences caused by the design or production, this can especially be caused by different poisoning or other aging of the pairs. This is explained in more detail further below.

[0143] If the detector-compensator pair Px is switched on, a voltage is applied both to the detector 10.x and to the compensator 11. In a first implementation, during the switched-on period of the pair Px, a voltage is applied both to the detector 10.x and to the compensator 11 continuously, preferably in a pulsed manner.

[0144] In a preferred implementation, during the time period when Px is switched on, the voltage is applied continuously only at the detector 10.x, preferably in a pulsating manner, while the voltage is applied only temporarily at the compensator 11. For example, Figure 4 The preferred implementation is realized by a circuit of . Since the compensator 11 is able to oxidize less target gas or even no target gas at all, its temperature is substantially affected by the applied voltage and the ambient temperature, and the ambient temperature generally changes significantly more slowly than the concentration of the target gas. Therefore, in many cases it is sufficient to measure the voltage or other detection variable applied to the compensator 11 once during the activation time interval and use the measured detection variable value of the compensator 11 throughout the activation time interval in which Px is turned on. The preferred implementation saves electrical energy and prolongs the service life of the compensator 11.

[0145] As already explained, harmful substances are often deposited on the heated detector 10 in the course of use. These deposits may limit or even completely prohibit the ability of the detector 10 to oxidize the combustible target gas. The detector 10 is then increasingly poisoned. A detector-compensator pair Px with a poisoned detector 10.x is generally no longer able to reliably detect the combustible target gas. The following describes a design scheme of how the gas detection device 100 according to the present invention can automatically identify the poisoning of the detector 10. Preferably, if a significant poisoning of the detector 10.x has been automatically identified, the detector-compensator pair Px with the detector 10.x is no longer connected. Because there are multiple detector-compensator pairs Px according to the present invention, the gas detection device 100 can still continue to be used. Therefore, the present invention extends the service life of the gas detection device 100.

[0146] In a preferred design, the detector is kept in reserve. Figure 5In the embodiment, this is the detector 10.8, which has a larger effective surface than the other detectors 10.1, ..., 10.7. "Kept reserved" means that the detector-compensator pair P.8 with the detector 10.8 is not switched on as long as no suspicion of poisoning of the other detectors 10.1, ..., 10.7 is detected.

[0147] It is possible that, especially because harmful substances have precipitated on the heated surfaces of the detectors 10.1, ..., 10.8, or due to other aging, at least one of the detector-compensator pairs P.1, ..., P.8 is poisoned. In this case, the pair with this detector cannot detect the target gas, and the measured value of the pair leads to an unduly low value of the target gas concentration. However, generally, the measured values of the poisoned or otherwise aged pairs do not lead to a significantly too high value of the target gas concentration.

[0148] The gas detection device 100 of the embodiment preferably detects the suspicion of poisoning as follows, i.e., during ongoing operation or during a special inspection phase: The control device 9 switches the pairs P.x on and off again in sequence. Each pair P.x provides a value of the detection parameter respectively. The evaluation unit 6 derives an estimated value con.x of the current target gas configuration for each switched-on pair P.x respectively. For this purpose, the evaluation unit 6 applies a pre-given functional relationship to the value of the detection parameter. The evaluation unit 6 thereby provides a time series con.x(1), con.x(2),... of the estimated values of the current target gas concentration. Each value con.x(1), con.x(2),... respectively relates to the sampling time points t(1), t(2),..., where t(1) < t(2) <.... Each pair P.x provides at least one value con.x(i) of the current target gas concentration respectively.

[0149] The evaluation unit 6 checks whether the target gas concentration rises or falls strongly between two successive sampling time points t(1), t(2),.... First, a first alternative, i.e., detecting a strong rise, is described.

[0150] For the following description, con.a(j) represents the value of the target gas concentration, which is derived based on at least one detection parameter value of the pair P.a (a = 1, ..., 7) and relates to the sampling time point t(j) (j = 1, 2, …). Denote the value of the pair P.b (b = 1, ..., 7) by con.b(j), and the value of the pair P.8 by con.8(j). As already mentioned and in Figure 5As shown, the detector 10.8 of the pair P.8 has a larger active surface than the remaining seven detectors 10.1, ..., 10.7. In addition, the pair P.8 is kept in reserve, i.e., is only switched on for testing and is therefore exposed to the load caused by harmful gases to a lesser extent than the remaining seven detectors 10.1, ..., 10.7. Therefore, it is assumed that the pair P.8 is always intact and provides correct values ​​until the gas detection device 100 is regularly tested.

[0151] The evaluation unit 6 checks whether the difference con.b(i)-con.a(i-1) between the target gas concentration values ​​at two consecutive sampling times t(i-1) and t(i) is greater than a predetermined absolute or relative limit, wherein the two values ​​con.a(i-1) and con.b(i) are determined from two different measurements of Pa and Pb, and wherein the limit can depend on the distance between t(i-1) and t(i). The value con.a(i-1) is provided for Pa and the value con.b(i) is provided for Pb.

[0152] A measured strong increase in the target gas concentration between the two sampling times t(i-1) and t(i) may have the following causes:

[0153] The target gas concentration actually increases strongly between the two sampling times t(i-1) and t(i), for example because a relevant amount of target gas escapes in the time interval between the two sampling times t(i-1) and t(i).

[0154] In fact, a high target gas concentration already exists at an earlier sampling time point. However, the Pa is poisoned so strongly that it is no longer possible to detect this high target gas concentration based on the measurement of Pa alone.

[0155] The two situations are now automatically distinguished from one another. To test the gas detection device 100 , the control device 9 activates pair P.8 .

[0156] The evaluation unit 6 derives the value con.8(i+1) of the target gas concentration from the measured value of P.8. The value con.8(i+1) relates to the subsequent sampling time t(i+1) and is considered to be correct. The evaluation unit 6 compares the value con.8(i+1) with the two values ​​con.a(i-1) and con.b(i). Depending on the result of the evaluation unit 6, the control device 9 triggers the following steps:

[0157] - If the larger value con.b(i) coincides with the value con.8(i+1) sufficiently accurately, then at least at the sampling times t(i) and t(i+1) there is actually a higher target gas concentration con.b(i) or con.8(i+1) than at the sampling time t(i-1) and this still has an effect on Pb.

[0158] - It can be checked whether the low value con.a(i-1) at the earlier sampling time t(i-1) is correct. The control device 9 starts the measurement of Pa and, based on the measurement of Pa, the evaluation unit 6 supplies the value con.a(t+2) relating to the sampling time t(i+2). If a large value con.a(t+2) is also supplied for Pa, then the target gas concentration actually increased strongly between the two sampling times t(i-1) and t(i) and this also acts on Pa.

[0159] Figure 6 The sequence is illustrated. The time t is plotted on the x-axis and the respectively measured target gas concentration con is plotted on the y-axis. The measured values ​​based on the measurement of Pa are indicated by a, the measured values ​​based on the measurement of Pb are indicated by b, and the measured values ​​based on the measurement of P.8 are indicated by solid circles.

[0160] If, however, a small value con.a(i+2) is supplied to Pa, the control device restarts P.8. This provides the value con.8(i+3) for the sampling time t(t+3). If a large value con.8(i+3) is supplied to P.8 again, the value con.a(i+2) is wrong and Pa is defective and is no longer used. Figure 7 Shows this situation.

[0161] If, however, a small value con.8(i+3) is also provided for P.8, the target gas concentration drops strongly again after the sampling time t(i+2). A possible reason for this is that the gas detection device 100 has moved from an area with a high target gas concentration to an area with a low target gas concentration or without target gas. Pa is then also continued to be used.

[0162] The second alternative will now be described, namely the detection of a strong drop. More precisely: the value con.b(i) for the sampling time t(i) is significantly lower than the value con.a(i-1) for the sampling time t(i-1). The evaluation unit 6 has already derived the value con.b(i) based on the measured value for Pb and the value con.a(i-1) based on the measured value for Pa.

[0163] The value con.8(i+1) is again used for the check, which relates to the sampling time t(i+1).

[0164] First, the following situation is described, that is, the value con.8 (i+1) considered to be correct is approximately as large as or even larger than the larger value con.a (t-1). In this case, the control device 9 switches the pair Pb back on. The measured value at the time of the re-connection leads to the value con.b (i+2), which relates to the sampling time t (i+2).

[0165] If the value con.b(i+2) for the sampling time point t(i+2) is approximately as large as the value con.8(i+1) which is considered correct, then the pair Pb is considered intact and continues to be used. Figure 8 Explain this situation.

[0166] If, however, the value con.b(i+2) for the sampling time t(i+2) is also significantly lower, for example approximately identical to the value con.b(i) for the sampling time t(i), then the pair P.8 is preferably switched back on. This provides the value con.8(i+3) for the sampling time t+3. If this value con.8(i+3) is again greater, then the pair Pb is defective and is no longer used. Fig. 9 Shows this situation.

[0167] As already explained, in this exemplary embodiment, only the pair P.8 is switched on for testing purposes. In one embodiment, all other pairs P.1, . . . , P.7 are switched on with the same frequency and for the same duration, for example in rotation.

[0168] In another embodiment, the process is as follows:

[0169] First, only the pair P.1 is used, wherein the pair P.1 is switched on and off again N times, N>=2. The remaining pairs P.2, ..., P.8 remain switched off. Subsequently, the pair P.2 is switched on and off again once. The last two measurements con.1(i-1) and con.2(i) are compared with one another, for example as further described above with reference to Figures 6 to 9 P.1 acts as pair Pa and P.2 acts as pair Pb. In the case of large deviations, pair P.8 is switched on and off again at least once.

[0170] If the check shows that both pairs P.1 and P.2 are still intact, the sequence just described is repeated, i.e. first pair P.1 is switched on and switched off again N times, and then P.2 is switched on and switched off again once. The remaining pairs remain switched off. Thus, pair P.1 is loaded N times more than P.2.

[0171] Since the pair P.1 is loaded N times more strongly, the pair P.1 is usually poisoned faster than the other pairs P.2 to P.8. If poisoning of the pair P.1 is detected, the pair P.1 is no longer used. The sequence just described is now carried out with the pairs P.2 and P.3. That is, first the sequence is carried out again, in which the pair P.2 is switched on and switched off again N times, and then the pair P.3 is switched on and switched off again once. The last two values ​​of the target gas concentration are compared with one another again. The pair P.2 acts as the pair Pa, and the pair P.3 acts as the pair Pb.

[0172] This action is carried out until P.1 to P.6 are poisoned so that self-control is no longer possible. It is also possible to switch one pair N times and the other pair M times, where N>M>1 applies. The above applies accordingly.

[0173] Reference numerals list

[0174]

[0175]

[0176]

Claims

1. A gas detection device (100) designed to detect the presence of at least one flammable target gas (CH4) in a gas sample and / or to determine the concentration of the target gas (CH4) in the gas sample, The gas detection device (100) comprises - a detection device (DA) having at least three detection units (10.m, 10.p, 10.1, ..., 10.8, 11.m, 11.p, 11), - measurement units (40, 40.10, 40.11, 41, 41.10, 41.11) and - an evaluation unit (6) for processing the signal, wherein at least two different detection units are detectors (10.m, 10.p, 10.1, ..., 10.8) and at least one other detection unit is a compensator (11.m, 11.p, 11), so that at least two different detector-compensator pairs (P.1, ..., P.8) are formed, each of which has exactly one detector (10.m, 10.p, 10.1, ..., 10.8) and exactly one compensator (11.m, 11.p, 11), wherein the number of the detectors is greater than the number of the compensators, wherein the compensator or at least one compensator (11) belongs to at least two different detector-compensator pairs (P.1, ..., P.8), wherein the gas detection device (100) is designed to switch each detector-compensator pair (P.1, ..., P.8) on and off independently of each other detector-compensator pair, wherein the gas detection device (100) is designed such that at each point in time at most one detector-compensator pair (P.1, . . . , P.8) is switched on and the other detector-compensator pair or each other detector-compensator pair is switched off, wherein, when the detector-compensator pair (P.1, ..., P.8) is switched on, a voltage (U10) is applied permanently or in a pulsating manner at least temporarily to the detector (10.m, 10.p, 10.1, ..., 10.8) and a voltage (U11) is applied permanently or in a pulsating manner at least temporarily to the compensator (11.m, 11.p, 11), wherein the respectively applied voltage (U10, U11) causes heating of the detector (10.m, 10.p, 10.1, ..., 10.8) and heating of the compensator (11.m, 11.p, 11), wherein each detector (10.m, 10.p, 10.1, ..., 10.8) is designed such that heating of the detector (10.m, 10.p, 10.1, ..., 10.8) causes oxidation of the target gas (CH4), wherein oxidation releases thermal energy which acts on the detector (10.m, 10.p, 10.1, ..., 10.8), wherein the or each compensator (11.m, 11.p, 11) is designed such that heating of the or each compensator (11.m, 11.p, 11) causes less oxidation of the target gas (CH4) or even no oxidation at all compared to heating of a detector (10.m, 10.p, 10.1, ..., 10.8), wherein each detector-compensator pair (P.1, ..., P.8) has a detection variable (ΔU, U10-U11) which is correlated with the thermal energy released by the detector-compensator pair (P.1, ..., P.8) during oxidation, wherein the measuring unit (40, 40.10, 40.11, 41, 41.10, 41.11) is designed to measure for each detector-compensator pair (P.1, ..., P.8): which value the detection variable (ΔU, U10-U11) assumes for this detector-compensator pair (P.1, ..., P.8), The evaluation unit (6) is designed to automatically - for each switched detector-compensator pair (P.1, ..., P.8) the measured value adopted for the detector-compensator pair (P.1, ..., P.8) according to the detection variable (ΔU, U10-U11) determining the presence of the target gas (CH4) and / or determining the target gas concentration, and The gas detection device (100) is designed for - switching on each detector-compensator pair (P.1, ..., P.8), - for the connected detector-compensator pairs (P.1, . . . , P.8), the corresponding detection variables (ΔU, U10-U11) are measured and evaluated, and - Switch off the detector-compensator pair (P.1, ..., P.8) again.

2. The gas detection device (100) according to claim 1, characterized in that: During a period of use of the gas detection device (100), at least one first detector-compensator pair (P.1, . . . , P.7) is switched on for a longer duration in total than a second detector-compensator pair (P.8).

3. The gas detection device (100) according to claim 2, characterized in that: The evaluation unit (6) is designed to determining the target gas concentration, comparing the target gas concentration estimate provided by the first detector-compensator pair (P.1, ..., P.7) with the target gas concentration estimate provided by the second detector-compensator pair (P.8), and If the two estimates differ from each other by more than a predefined limit, one of the following steps is triggered: - changing the value of a parameter, wherein the evaluation unit (6) uses the parameter value to determine the presence of a target gas (CH4) and / or to determine the target gas concentration based on the measured values ​​of the first detector-compensator pair (P.1, ..., P.7), or - Deactivating said first detector-compensator pair (P.1, ..., P.7).

4. The gas detection device (100) according to claim 2 or claim 3, characterized in that the gas detection device (100) is designed to in a usage period, switch on and switch off the first detector-compensator pair (P.1,..., P.7) N1 times, and switch on and switch off the second detector-compensator pair (P.8) N2 times, where N1 and N2 are two quantities, and N1 is greater than N2.

5. The gas detection device (100) according to any one of claims 2 to 4, characterized in that the gas detection device (100) is designed to execute the sequence at least once in a usage period, wherein during this sequence, - first switch on and switch off the first detector-compensator pair (P.1,..., P.7) N times, - then switch on and switch off the second detector-compensator pair (P.8) M times, where M and N are two quantities, and 0 < M < N applies.

6. The gas detection device (100) according to any one of the foregoing claims, characterized in that at least one detector-compensator pair (P.1,..., P.8) is designed such that the two detection units (10, 11) of the detector-compensator pair (P.1,..., P.8) respectively have detection parameters (U10, U11), where the corresponding detection parameters (U10, U11) are related to the temperature of the detection units (10, 11), and where the measurement unit is designed to measure, in the case of the switched-on detector-compensator pair (P.1,..., P.8): which value the detection parameter (U10) of the detector (10.1,..., 10.8) takes and which value the detection parameter (U11) of the compensator (11) takes.

7. The gas detection device (100) according to claim 6, characterized in that the gas detection device (100) is designed to operate the detector-compensator pair (P.1,..., P.8) using two detection parameters (U10, U11), such that first one detection unit (10.1,..., 10.8) of the detector-compensator pair (P.1,..., P.8) and then the other detection unit (11) are switched on and switched off again, such that at each time point within the activation time interval during which the detector-compensator pair (P.1,..., P.8) is switched on, at most one detection unit (10.1,..., 10.8, 11) of the detector-compensator pair (P.1,..., P.8) is switched on.

8. The gas detection device (100) according to claim 6 or claim 7, characterized in that the gas detection device (100) is designed to operate the detector-compensator pair (P.1,..., P.8) using two detection parameters (U10, U11), so that the measuring unit (40, 40.10, 40.11, 41, 41.10, 41.11) is switched on during an activation time interval of the detector-compensator pair (P.1, ..., P.8), measuring the value of the detection variable (U10) of the detector (10.1, ..., 10.8) more frequently than the value of the detection variable (U11) of the compensator (11), The value of the detection variable (U11) of the compensator (11) is preferably measured exactly once.

9. A gas detection device (100) according to any one of the preceding claims, characterized in that The detection device (DA) extends in a plane and its largest dimension perpendicular to the plane is at most 20%, preferably at most 10%, particularly preferably at most 5% of the largest dimension in the plane, In this case, the detection units (10.m, 10.p, 10.1, . . . , 10.8, 11.m, 11.p, 11) are arranged in at least one row without overlapping, as seen in a viewing direction perpendicular to the plane.

10. The gas detection device (100) according to claim 9, characterized in that: In the row or a row in which a plurality of detection units (10.m, 10.p, 10.4, 10.5, 10.2, 10.7, 11.m, 11.p, 11) are arranged, the compensator (11) or a compensator (11) is arranged between two detectors (10.4, 10.5, 10.2, 10.7).

11. A gas detection device (100) according to any one of the preceding claims, characterized in that The detection device (DA) comprises at least three detectors (10.1, ..., 10.8), wherein at least three detectors (10.1, . . . , 10.8) and the compensator (11) or a compensator (11) extend in the same plane, and In the plane, the compensator (11) or a compensator (11) is arranged between at least two detectors (10.4, 10.5, 10.2, 10.7) of at least three detectors (10.1, . . . , 10.8).

12. The gas detection device (100) according to any one of the preceding claims, characterized in that The detection device comprises a circuit board (31), and Each detection unit (10.m, 11.m) comprises a heating element (32), When a voltage (U10, U11) is applied to the detection unit (10.m, 11.m), the heating element (32) of the detection unit (10.m, 11.m) is heated, The heating element (32) is arranged on the circuit board (31) and / or in the circuit board (31), The circuit board (31) provides an electrical contact (46) for each heating element (32), and The respective heating element (32) of each detector (10.m) is covered with a coating (35) which comprises a catalytic material or a catalytic material (24) is applied to the coating.

13. A gas detection device (100) according to any one of the preceding claims, characterized in that The detection device (DA) comprises a third detector-compensator pair (P.8) and the evaluation unit (6) is designed to determine the target gas concentration, The evaluation unit (6) is designed to - comparing the target gas concentration estimate provided by the first detector-compensator pair (P.1) with the target gas concentration estimate provided by the second detector-compensator pair (P.2, ..., P.7), and The third detector-compensator pair is at least temporarily switched on only if the two estimated values ​​differ from one another by more than a predefined limit (P.8).

14. The gas detection device (100) according to claim 13, characterized in that Each detector (10.m, 10.p, 10.1, ..., 10.8) has an effective surface in contact with the gas sample, The detector (10.8) of the third detector-compensator pair (P.8) has a larger active surface than the detector of the first detector-compensator pair (P.1) and than the detector of the second detector-compensator pair (P.2, . . . , P.8).

15. The gas detection device (100) according to any one of the preceding claims, characterized in that for each detector-compensator pair (P.1, ..., P.8), a zero value is predefined, which is the value that the detection variable (ΔU, U10-U11) of the detector-compensator pair (P.1, ..., P.8) assumes in the absence of target gas (CH4), wherein the evaluation unit (6) is designed to calculate, for each detector-compensator pair (P.1, . . . , P.8), a difference between the value assumed by the detection variable (ΔU, U10-U11) and a predetermined zero value of the detection variable, and For each detector-compensator pair (P.1, ..., P.8) that is switched on, The presence of the target gas (CH4) and / or the concentration of the target gas are determined based on the difference between the measured detection parameter value and the zero value.

16. A gas detection method for detecting the presence of at least one combustible target gas (CH4) in a gas sample and / or determining the concentration of the target gas (CH4) in the gas sample using a gas detection device (100), The gas detection device (100) comprises - a detection device (DA) having at least three detection units (10.m, 10.p, 10.1, ..., 10.8, 11.m, 11.p, 11) and - measuring units (40, 40.10, 40.11, 41, 41.10, 41.11), wherein at least two different detection units are detectors (10.m, 10.p, 10.1, ..., 10.8) and at least one other detection unit is a compensator (11.m, 11.p, 11), so that at least two different detector-compensator pairs (P.1, ..., P.8) are formed, each of which has exactly one detector (10.m, 10.p, 10.1, ..., 10.8) and exactly one compensator (11.m, 11.p, 11), wherein the number of the detectors is greater than the number of the compensators, wherein the compensator or at least one compensator (11) belongs to at least two different detector-compensator pairs (P.1, ..., P.8), The method comprises the steps of automatically performing - switching on at least one, preferably each, detector-compensator pair (P.1, . . . , P.8), - for the switched detector-compensator pairs (P.1, . . . , P.8), the detection variables (ΔU, U10-U11) are measured and evaluated, and – switching off the detector-compensator pair (P.1, ..., P.8) again, wherein at each point in time at most one detector-compensator pair (P.1, . . . , P.8) is switched on and the or each other detector-compensator pair is switched off, wherein, when the detector-compensator pair (P.1, ..., P.8) is switched on, a voltage (U10) is at least temporarily applied to the detector (10.m, 10.p, 10.1, ..., 10.8) and a voltage (U11) is at least temporarily applied to the compensator (11.m, 11.p, 11), wherein the respectively applied voltage (U10, U11) causes heating of the detector (10.m, 10.p, 10.1, ..., 10.8) and heating of the compensator (11.m, 11.p, 11), wherein the heating of the detector (10.m, 10.p, 10.1, ..., 10.8) causes oxidation of the target gas (CH4), wherein the oxidation releases thermal energy, which acts on the detector (10.m, 10.p, 10.1, ..., 10.8), wherein the heating of the compensator (11.m, 11.p, 11) causes less oxidation or even no oxidation at all compared to the heating of a detector (10.m, 10.p, 10.1, ..., 10.8), wherein each detector-compensator pair (P.1, ..., P.8) has a detection variable (ΔU, U10-U11) which is correlated with the thermal energy released by the detector-compensator pair (P.1, ..., P.8) during oxidation, and The method comprises the following further automatically executed steps: for each detector-compensator pair (P.1, ..., P.8) that is switched on, The measuring unit (40, 40.10, 40.11, 41, 41.10, 41.11) measures: which value the detection variable (ΔU, U10-U11) assumes for the detector compensator pair (P.1, ..., P.8), and - measured values ​​adopted for the switched detector-compensator pairs (P.1, . . . , P.8) according to the detection variables (ΔU, U10-U11) The presence of the target gas (CH4) is determined and / or the concentration of the target gas is determined.

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