Abstract:
A method for recognizing sensor poisonings in portable gas-measuring devices with a test station having a main unit with a control and analysis unit and test modules connected with the main unit for data exchange with an connected device. The test station recognizes device model and/or gas sensor model of the connected device. The main unit has gas inlets for different test gases and there is a first gas feed line for sending test gas to the test modules and a second gas feed line for sending purging gas to the test modules and a gas drain line to return gas from the test modules to the main unit. The method includes detection of a first measured value and of a second measured value and determination of sensor poisoning on the basis of the two values. The test station control and analysis unit carries out the method.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2013 008 425.3 filed May 16, 2013, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a method for recognizing sensor poisonings in portable gas-measuring devices by means of a test station as well as to a test station for carrying out this method. 
       BACKGROUND OF THE INVENTION 
       [0003]    Portable gas-measuring devices are usually used by persons who are located in areas in which they may be exposed to harmful gases. Such gas-measuring devices may be equipped with different models of sensors, e.g., infrared sensors, semiconductor sensors, electrochemical sensors, catalytic sensors or the like. However, the phenomenon of the so-called sensor poisoning plays a major role in respect to the ability of the gas sensor and hence of the gas-measuring device to function especially in the case of catalytic sensors. 
         [0004]    Such catalytic sensors typically recognize not only a special gas, but there are so-called cross sensitivities, i.e., the sensor recognizes a plurality of different gases simultaneously, without being able to concretely indicate which of these gases it is actually measuring. However, the sensitivity to these gases may be different. The sensitivity to the recognized gases decreases in the course of the aging of such sensors. However, the sensitivity does not decrease uniformly for all recognized gases. The process is rather affected by the concrete history of the individual gas sensor, i.e., by the ambient and storage conditions and the gas species and quantities of gases to which the sensor was already exposed in the course of its life. However, the sensor may be damaged or poisoned above all by certain substances. Among others, substances such as silicon, sulfur compounds and polymerizing substances lead to such a poisoning in case of catalytic EX sensors (sensors that are used in an environment with potential explosion hazard and/or can detect explosible/explosive gases). One speaks of sensor poisoning in this connection if a certain gas or vapor to be detected cannot be processed in the catalytic sensor any longer and thus it cannot be detected any longer, or when the sensitivity is insufficiently low to initiate the necessary actions, e.g., alarms. The sensor in this case indicates a measurement result that is much too low compared to the actually present concentration of the gas to be detected. It may in this case happen that a sensor, which can measure a plurality of different gases, continues to correctly indicate a first gas, but it does not any longer correctly measure a second gas, for which it is already poisoned. This is especially significant if the calibrating gas, i.e., the gas with which the sensor sensitivity is set, corresponds to the gas for which the normal sensitivity was maintained. The loss of sensitivity for the second gas can thus remain suppressed. 
         [0005]    Such a sensor poisoning may become especially relevant, for example, in case of catalytic sensors that shall detect combustible gases, e.g., in the area of firefighting, but also in the petrochemical industry, chemical industry or in mining. Such catalytic sensors can also recognize, besides methane, for example, different other gases and vapors, e.g., propane, pentane, butane or nonane and toluene or the like. For example, sensors that are used in the area of firefighting and shall indicate the presence of combustible gases or vapors, are often set by means of toluene or nonane, because they have a comparatively low sensitivity to these vapors. It is in this case assumed that a sensor thus set will adequately detect the entire range of combustible gases and vapors. However, it may be problematic that the sensitivity of the sensor to toluene and nonane is often retained for a long time, while the sensitivity to, e.g., methane declines much sooner, which is also called selective sensor poisoning for methane (or another corresponding gas). The gas sensor in this case measures the quantity of all gases present as a so-called sum signal, i.e., as a sum of a plurality of signals. The sum is composed of the individual measured values of the gases present. It cannot be recognized on the basis of the sum how high the actual percentage of the particular gases measured is. At the same time, the gas sensor is typically also unable to resolve the sum signal into the individual components. Thus, there may be a risk that the actually present concentrations of individual combustible gases, especially methane, but also of another gas, for which the sensor is already poisoned, is estimated incorrectly at an operating site. This may lead to drastic consequences for the user of the gas-measuring device in the worst case. 
         [0006]    For example, US 2008/0257732A1, US 2006/0019402A1, and U.S. Pat. No. 5,670,115 A describe in this connection that sensor poisonings are determined by means of various calibrating or test gases, and the gas sensor to be tested is exposed to the calibrating or test gases one after another. 
         [0007]    Test stations for gas-measuring devices, in which different test gases can be admitted simultaneously to a plurality of gas-measuring devices, are known from the documents JP 2006-003 115 A, U.S. Pat. No. 7,530,255 B2, and WO 2013/019178 A1. 
       SUMMARY OF THE INVENTION 
       [0008]    Based on this, an object of the invention is to provide a method and a test station for carrying out the method, with which method the risk of incorrect estimation of a present concentration of a gas can be reduced. 
         [0009]    In a method for recognizing sensor poisonings in portable gas-measuring devices by means of a test station, wherein the test station has a main unit including a control and analysis unit and wherein the test station has a plurality of test modules, which are connected with the main unit for data exchange, and into which a gas-measuring device each can be inserted (connected), wherein the test station has means for recognizing the model of the device for detecting the model of the device and/or the model of the gas sensor of the particular gas-measuring device inserted into a test module, wherein the main unit has a plurality of gas inlets for different test gases and wherein the test station has a first gas feed line, through which test gas can be sent to the test modules, a second gas feed line, through which a purging gas can be sent to the test modules, and a gas drain line, through which gas can be sent from the test modules back to the main unit, the present invention makes provisions for the method to have the following steps:
       a. Insertion of at least one gas-measuring device into at least one of the test modules of the test station;   b. Recognition of the model of the gas sensor of the gas-measuring device inserted and/or of the model of the gas-measuring device inserted by the means for recognizing the device model of the test station;   c. Transmission of the recognized gas sensor model and/or of the model of the device of the gas-measuring device inserted at the control and analysis unit;   d. Selection of a first test gas suitable for the model of the gas sensor of the gas-measuring device inserted by the control and analysis unit;   e. Connection of the gas inlet, through which the selected test gas can be fed, to the first gas feed line in the test station;   f. Feeding of the first test gas to the test module, in which the gas-measuring device is inserted;   g. Detection of a first measured value by the gas sensor;   h. Optionally: Purging of the gas-measuring device and of the gas sensor by means of a purging gas, which is sent through the second gas feed line from the main unit to the test module, in which the gas-measuring device is inserted;   i. Selection of a second test gas suitable for the model of the gas sensor of the gas-measuring device inserted by the control and analysis unit;   j. Connection of the gas inlet, through which the selected second test gas can be fed, to the first gas feed line in the test station;   k. Feeding of the second test gas to the test module, in which the gas-measuring device is inserted;   l. Detection of a second measured value by the gas sensor; and   m. Determination whether a sensor poisoning is present on the basis of the first measured value detected and the second measured value detected.       
 
         [0023]    A first gas feed line, through which test gas can be sent to the test modules, will also be called test gas feed line (test gas line) below. The second gas feed line, through which purging gas can be sent to the test modules, will also be called purging gas line (purging gas feed line). 
         [0024]    Whether a sensor poisoning possibly occurs can be determined rapidly and in a simple manner based on the first and second measured values by means of the test station with such a method. For example, information on the measured value, that is ideally expected (expected measured value) for the particular model of gas sensor (sensor model) for a certain gas at a preset concentration of the gas in a gas mixture, can be stored for this in the control and analysis unit. 
         [0025]    The analysis can then be based on the knowledge of the cross sensitivities of the two gases to one another. For example, the indicated measured value of the two gases is put into relationship with one another. If the value is below a limit, which can be considered to be sufficiently safe from the viewpoint of the protection of persons, it is meaningful to classify the sensor as being poisoned. For example, a value for the lower explosion limit (LEL) of a gas in a gas mixture may be stored for this. It may also be provided that a value that is markedly lower than the lower explosion limit, e.g., 50% of the lower explosion limit (50% LEL), is stored to ensure that the presence of corresponding combustible gases is detected in time in all cases. 
         [0026]    Catalytic sensors, which detect a plurality of different such gases due to corresponding cross sensitivities, are typically not uniformly sensitive for all these gases. There are, for example, sensors that indicate, when exposed to a gas that contains methane at a concentration corresponding to 50% LEL, that methane is contained at a concentration of 50% LEL. However, when exposed to propane at a concentration of 50% LEL, the same sensor indicates only that propane is present at a concentration of 29% LEL. Such an exemplary sensor would therefore be expected, when exposed to a corresponding gas, to indicate 50% LEL for methane corresponding to 50% LEL and to indicate 29% LEL for propane. The expected measured value would be correspondingly 50% LEL for methane and 29% LEL for propane. Such values are usually known for the respective models of sensors and can therefore be correspondingly stored in the control and analysis unit. 
         [0027]    In a very simple embodiment, it is possible, for example, for catalytic sensors, which are used as a primary measure in the protection against personal injuries due to explosions, to check whether after adjusting to the first, more insensitive gas, the second, more sensitive gas reaches at least the concentration that was fed. Thus, even though the ratio would drop to 1:1, but triggering an alarm in due time would still always be guaranteed. 
         [0028]    To recognize selective poisonings in time, it is, however, recommended that a sensor-specific value be determined, which must not be undershot. This value can be determined experimentally. It is consequently advantageous if the test station with which the method is carried out is a test station in which measured values expected in the control and analysis unit are stored for a plurality of gas sensor models and/or for gases that are to be measured. What measured values are stored in the individual gas sensor models depends logically on the particular gas sensor model. 
         [0029]    It may also be provided in this connection that information is stored in the control and analysis unit for individual models of gas sensors on which gas mixture can be used as the first test gas, which gas mixture as the second test gas, what measured value is expected in case of exposure to the first test gas and what measured value is expected on exposure to the second test gas. It may also be provided, as an alternative, that information is stored on which gas mixture can be used as the first test gas, which gas mixture can be used as the second test gas and on the ratio of the first measured value that is expected on exposure to the first test gas to the second measured value that is expected on exposure to the second test gas. 
         [0030]    To determine whether a gas-measuring device or a gas sensor, which is used in a gas-measuring device, is still sufficiently in good working order to recognize a hazardous situation in time and reliably, the following procedure can then be followed by means of the method according to the present invention. 
         [0031]    The gas-measuring device to be tested, i.e., the gas-measuring device in which a gas sensor to be tested is installed, is inserted into a test module corresponding to the steps a. through c. of the method according to the present invention. The test station in this case recognizes the gas-measuring device model that was inserted or what gas sensor model or, if a plurality of gas sensors are installed in the gas-measuring device, the gas sensor models the gas-measuring device inserted contains. The test station can preferably recognize both, i.e., the test station recognizes the model of gas-measuring device that was inserted and the model of gas sensor or the models of gas sensors that are installed in the gas-measuring device. This is advantageously carried out by means of the device model recognition means. Each test module advantageously has such a device model recognition means. The test module then transmits the recognized information via corresponding data exchange means, by which the test module is connected with the main unit for data exchange, to the control and analysis unit of the main unit. 
         [0032]    Based, as was described above, on data stored in the control and analysis unit of the main unit, the control and analysis unit of the test station then selects, corresponding to step d. of the method according to the present invention, a first test gas, with which it can be determined, in principle, whether the gas sensor of the gas-measuring device, which said gas sensor is to be tested, is in good working order. A test gas is a gas mixture that contains one or more gases of a known composition. A gas mixture is defined, in principle, as a gas that contains one or more different gases with a known or unknown composition. If it shall be checked, for example, whether a catalytic sensor detects combustible gases correctly, the first test gas may be, for example, a gas mixture that contains combustible gases with a known composition. 
         [0033]    The test station with which the method is carried out has a plurality of gas inlets, to which, for example, a pressurized gas cylinder each, which contains a certain test gas, can be connected. This is especially advantageous if the selection of test gases shall be able to be chosen individually. Individual pressurized gas cylinders can be replaced rapidly and simply in this case, as a result of which different test gases can correspondingly be made available, depending on the individual requirements of the operator of the test station. However, it may also be provided that stationary gas feed lines for such test gases are connected to the gas inlets. The control and analysis unit of the main unit of the test station in this case has corresponding information on what test is connected to which gas inlet. This can be recognized either by the control and analysis unit by means of a recognition device, or it is programmed correspondingly in the control and analysis unit by the operator of the test station. Corresponding connection data may, of course, also be preset and stored in the control and analysis unit. After the control and analysis unit of the test station has selected the suitable first test gas, it gives a prompt for the gas inlet through which the selected test gas can be fed to become connected, corresponding to step e. of the method according to the present invention, to become connected with the first gas feed line of the test station. This can take place, for example, by sending a corresponding control command to one or more valves in the test station. 
         [0034]    If the corresponding gas port of the main unit is connected with the first gas feed line (connected to the first gas feed line), the test station can send, corresponding to step f. of the method according to the present invention, the first test gas to the test module, into which the gas-measuring device to be tested is inserted. The gas-measuring device will then measure the first test gas fed to it in just the same way as it would measure any other gas mixture during use in a real situation, and it sends a first measured value. Adjustment may optionally also be made to the first measured gas in this step, i.e., the first measured value is corrected such that it corresponds to the concentration in the test gas cylinder. This first measured value is detected by the test module and preferably transmitted by means of the data exchange means to the main unit, namely, to the control and analysis unit of the test station. A first measured value of the gas sensor is thus detected corresponding to step g. of the method according to the present invention. If the gas-measuring device to be tested contains a plurality of gas sensors, it is conceivable that steps d. through g. are carried out separately for each of these gas sensors. 
         [0035]    To remove residues of the first test gas from the gas-measuring device to be tested following this first measurement and to thus prevent the subsequent second measurement from being possibly distorted, it may be useful to purge the gas-measuring device with a purging gas in a next step. The method according to the present invention therefore provides for the purging of the gas-measuring device inserted and of the gas sensor as an optional step h. by means of a purging gas, which is sent through the second gas feed line from the test station to the test module, into which the gas-measuring device is inserted. A purging gas is typically a neutral (inert) gas, in which the gas sensor does not detect any gases that are to be detected. This may be, for example, normal air. Depending on the environment in which the test station is used, this air may be fed through a pressurized cylinder, or it may also be taken up from the ambient air, for example, by means of a pump. The test station advantageously has a gas port for this in its main unit, which port can be connected either with a corresponding purging gas cylinder or with the ambient air. This gas port is preferably connected with the second gas feed line of the test station. The purging gas can be sent through this second gas feed line to the test modules, and the control and analysis unit of the test station can transmit the command for switching over from the first gas feed line to the second gas feed line to the test modules. The transmission preferably takes place via data exchange means. It may also be provided, as an alternative, that each test module has a control unit (test module control unit) of its own. This test module control unit can then control a switchover from the first gas feed line to the second gas feed line, which switchover is independent from the main unit. 
         [0036]    Regardless of whether step h. is performed after detection of the first measured value or not, a second measured value is detected corresponding to the method according to the present invention by carrying out steps i. through l., in order to be finally able to determine, in step m., whether a sensor poisoning is possibly present. Steps i. through l. are carried out as was already described above for steps d. through g., step i. being carried out analogously to step d, step j. analogously to step e., step k. analogously to step f., and step l. analogously to step g. It is recognized that it is also readily possible in an alternative order in which the method is carried out to carry out step i. (selection of a second test gas suitable for the model of the gas sensor) already immediately after step d. and hence before step e. 
         [0037]    To determine, corresponding to step m., whether sensor poisoning is present, the first measured value, which was detected in step g., and the second measured value, which was detected in step l., are compared with the respective expected measured values. The comparison may be carried out automatically by the control and analysis unit. However, it may also be provided that the control and analysis unit only passes on the actual measured values and the corresponding expected measured values to an output unit and an operator of the test station decides on the basis of this information whether or not sensor poisoning is present. It may also be provided, for example, that the operator receives the expected and actual measured values displayed on a display device (display), that the expected and actual measured values are outputted via a printing device, or even that these are transmitted to another terminal, e.g., a computer of the operator, and are analyzed there by the operator. However, the control and analysis unit preferably performs the comparison automatically and outputs only the result, namely, the determination of whether or not sensor poisoning is possibly present. It is even conceivable, in an especially preferred manner, that the control and analysis unit outputs the result in the form of a control command, which it selects on the basis of the result. Various scenarios are conceivable, e.g., the following: If the control and analysis unit arrives at the result that a sensor poisoning is possibly present, this control command may be, for example, that the corresponding gas-measuring device is blocked from further use. It may also be provided that the control command is the sending of a warning signal, the blocking of the removal of the gas-measuring device from the test module or something similar. 
         [0038]    In any case, the result is determined by comparison of the first measured value with the second measured value. For example, the ratio of the first measured value to the second measured value can be formed. If the two measured values essentially correspond to the expected measured values or they deviate from the expected measured values by a constant error, which is generated by an incorrect setting of the sensor only, the ratio of the two measured values corresponds to the ratio of the expected measured values. If, however, there is sensor poisoning, the error with which the first measured value deviates from the expected first measured value from the error with which the second measured value deviates from the expected second measured value. As a consequence, the ratio of the first measured value to the second measured value also deviates significantly from the ratio of the expected first measured value to the expected second measured value. The limits within which a deviation of the ratio of the real measured values from the ratio of the expected measured values are considered to be a significant deviation may be stored preferably for each gas-measuring device to be tested or for each model of gas sensor to be tested in the control and analysis unit. It may also be provided that these limits are set and programmed by the operator when the test station is put into operation or during the operation of the test station. 
         [0039]    It may also be provided that in case of a non-automatic analysis, in which the values are only displayed, for example, to the operator, the measured values or the ratios of the measured values are checked only by the operator comparing them, for example, with values present in tables or in another form or by a similar procedure. As an alternative to the comparison of the measured value ratios formed as described above, it may also be provided in such a case that a direct comparison of the measured values with the expected values is performed. For example, the operator can determine in this case for each measured value how great the error is by which the real measured value deviates from the expected measured value and then compare the errors with one another. If the two measured values deviate from the expected values by an equal error or an error that is similar within narrow limits, sensor poisoning is very likely to be absent and there is only an incorrect adjustment of the sensor by this more or less constant error. However, if the errors deviate markedly from one another, there is a possibility that a sensor poisoning is present. It is obvious that this procedure can also be carried out automatically by the control and analysis unit of the test station. 
         [0040]    It is thus favorable in any case if the determination of whether a sensor poisoning is present in step m. comprises the following steps:
       m.1 Transmission of the first measured value and of the second measured value to the control and analysis unit of the test station;   m.2 Determination of the ratio of the first measured value to the second measured value; and   m.3 Outputting of the ratio by means of an output unit and/or selection of a follow-up action by the control and analysis unit of the test station on the basis of the ratio determined.       
 
         [0044]    Step m.2 may also be, as an alternative, a determination of the ratio of the errors by which the real first measured value, i.e., the first measured value detected in step g., deviates from the expected first measured value and by which the real second measured value, i.e., the second measured value detected in step l., deviates from the expected second measured value, as was explained above. 
         [0045]    If only the ratio is outputted in step m.3 without a further follow-up action being selected by the test station, the operator can select an individual subsequent reaction on the basis of this outputted information. 
         [0046]    The selection of a follow-up action by the control and analysis unit is advantageously performed by a comparison of the ratio determined in step m.3 with a ratio being stored in the control and analysis unit. The control and analysis unit in this case determines by how much the determined ratio deviates from the stored ratio and selects a follow-up action in the form of a control command on the basis of the result obtained in this case for the deviation. If no ratios are being stored in the control and analysis unit, but only individual expected measured values, the control and analysis unit may also form first the ratio of the expected measured value for selecting the follow-up action and subsequently compare this ratio with the ratio of the real measured values detected in steps g. and l. 
         [0047]    It is recognized that it is always advantageous if the first test gas contains a gas that is to be measured during the operation of the gas-measuring device at a first, known concentration and if the second test gas contains the gas to be measured at a second, known concentration, which is different from the concentration of the gas in the first test gas. It may also be advantageous in this case if the second test gas contains, in addition to the gas to be measured, at least one gas for which the gas sensor model present in the gas-measuring device inserted has cross sensitivity. It is especially favorable in this connection, if the gas for which there is cross sensitivity is not a component of the first test gas. The first and/or second test gas may be selected especially preferably from the group containing propane, propane mixed with H 2 S, CO, O 2  and/or CO 2 , pentane, pentane mixed with H 2 S, CO, O 2  and/or CO 2 , butane, hydrogen as well as mixtures of these gases and gas mixtures mentioned. Further gaseous or vapor components may also be added, e.g., toluene, nonane, methane, propane, butane, hydrogen, pentane or even mixtures thereof. 
         [0048]    In a method according to the present invention, in which the test station is advantageously designed such that each test module has a gas feed line, which can be connected with a gas inlet of the gas-measuring device to be tested, which said line has a first feed valve and a second feed valve and which can be connected with the first gas feed line via the first feed valve and with the second gas feed line via the second feed valve, the present invention preferably makes, in addition, provisions for the feeding of the first test gas to the test module in step f. and for the feeding of the second test gas to the test module in step k. to contain the following respective steps: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 f.1 and k.1 
                 Closing of the second feed valve; 
               
               
                   
                 f.2 and k.2 
                 Opening of the first feed valve. 
               
               
                   
                   
               
             
          
         
       
     
         [0049]    As was already described above, the first gas feed line is the test gas feed line and the second gas feed line is the purging gas feed line here as well. The gas inlet of the gas-measuring device to be tested is the gas inlet via which the gas-measuring device draws in the gas to be measured during intended use. 
         [0050]    It may also be provided in any case that a plurality of gas-measuring devices can be inserted simultaneously into the test station. The gas-measuring devices may also be inserted at different times into the test station. The respective test module, in which a gas-measuring device is inserted at any desired time, then transmits, independently from the other test modules of the test station, the information to the main unit that a gas-measuring device was inserted and which gas sensor model or which gas sensor models and/or which device model was recognized. The control and analysis unit can then select the corresponding first test gas, likewise independently from the state of the other test modules. 
         [0051]    Furthermore, steps h. and i. as well as m. of the method according to the present invention can be carried out for each test module, into which a gas-measuring device was inserted, independently from the state of the remaining test modules. In other words, the control and analysis unit can determine, for example, for a certain test gas, which can be fed via one of the gas inlets to the first gas feed line of the test station, for which test modules this test gas is needed either as a first test gas or as a second test gas. 
         [0052]    By contrast, steps e. through g. and steps j. through l. are preferably carried out synchronously for all test modules of the test station. Steps e. and j. and steps f. and k. as well as steps g. and i. can be carried out simultaneously for different test modules that are fundamentally different from one another. However, it is useful if each test module performs all steps a. through m. at least once for each gas-measuring device that is inserted into the test module. 
         [0053]    The following would be, for example, a conceivable course of such a method: By performing steps a. through d. or by performing step i. for all test modules independent from one another, the control and analysis unit determines, as was described above, which test gas the individual test modules need in the respective next step, i.e., step e. or step j. The control and analysis unit then determines which of these needed test gases shall be sent as the next gas through the first gas feed line of the test station. The feed of the test gas from the first gas feed line is then interrupted, preferably for all test modules that do not need this test gas, by closing the feed valve that is arranged between the test gas feed line and the respective test module. As a consequence, only the test modules that need the same test gas in the next step are connected with the first gas feed line fluidically. Corresponding to steps e. and j., respectively, the gas inlet, through which the selected test gas can be fed, is then connected as the next step to the first gas feed line in the test station and the test gas is sent to the test modules as described above corresponding to steps f. and k., respectively. Finally, a measured value is determined according to steps g. and l., respectively, for each test module, consequently for each gas-measuring device to which the test gas was admitted in the preceding step. It is then determined again for all test modules, independently from one another, whether the gas-measuring device in question has already run through all steps a. through l. and whether it is thus possible to carry out step m. for the test module in question or the gas-measuring device inserted. It is possible to perform step m. when both a first measured value and a second measured value were detected for the test module in question or the gas-measuring device inserted into the test module in question. Step m. is carried out for the test modules for which it is possible to carry out this step. The corresponding, still missing measured value is detected corresponding to the above-described method for the test modules for which it is not possible to carry out step m. 
         [0054]    It is consequently recognized that in case a plurality of gas-measuring devices are or will be inserted into the test station, it is advantageous if the method has the following steps:
       A Carrying out of steps a. through d. and/or carrying out of step i. for each of the gas-measuring devices independently from one another;   B Determination by means of the control and analysis unit which of the test modules are equipped with gas-measuring devices and which of these gas-measuring devices need the same test gas as the next test gas;   C Closing of the feed valve that is arranged between the test gas feed line and the respective test module for all test modules that do not need the test gas selected in B in the next step; and   D Carrying out steps e. through h. or steps j. through m. for each of the gas-measuring devices determined in B independently from one another;
 
wherein each of the steps a. through m. is carried out at least once for each gas-measuring device that is inserted into a test module of the test station. However, it is also useful if steps a. through m. are carried out for each test module into which a gas-measuring device is inserted in the above-described order from a. to m. However, it may also be provided that the steps are carried out in the order a., b., c., d. i., e., f., g., h., j., k., l., m. or in the order a., b., c., d., i., j., k., l., h., e., f., g., m., and step h. is an optional step, which may be carried out in any case, as before, at any other desired point and/or at a plurality of points of the method.
       
 
         [0059]    On the whole, the course of the method for a gas-measuring device that is inserted into a test module when other gas-measuring devices are already present in the test station for testing is in this case, for example, as follows:
       Insertion of the gas-measuring device into one of the test modules corresponding to step a. The gas-measuring device is preferably inserted when the feed valve that is arranged between the first feed line and the respective test module is closed,   Recognition of the model of the device and/or of the gas sensor corresponding to step b.,   Transmission of the recognized model of the device and/or of the model of the gas sensor corresponding to step c.,       
 
         [0063]    Selection of the first test gas by the control and analysis unit corresponding to step d. and/or selection of the second test gas by the control and analysis unit corresponding to step i.,
       Waiting until one of the two test gases selected previously is the test gas that shall be sent next through the first gas feed line,   Connection of the gas inlet, through which the selected test gas can be fed, to the first gas feed line in the test station, feeding of the test gas to the test module and detection of a first measured value,   Determination that step m. cannot yet be carried out because two measured values have not yet been determined,   Selection of the second test gas unless this was done already before,   Waiting until the second of the two test gases selected previously is the test gas that shall be sent as the next gas through the first gas feed line,   Connection of the gas inlet through which the selected test gas can be fed to the first gas feed line in the test station, feeding of the test gas to the test module and detection of a first measured value, and   Determination that step m. can be carried out and carrying out of step m.       
 
         [0071]    Further variants of this course are, of course, conceivable as well. For example, it is conceivable that a gas-measuring device is inserted into a test module, which contains a plurality of gas sensors, for which the above-described method is carried out independently from one another. It is advantageous, for example, in this case if both the model of the device and the model or models of the gas sensor/gas sensors of the device are recognized in step b. of the method. 
         [0072]    Moreover, it is conceivable that so-called filter breakthroughs can be detected by means of the method according to the present invention. For example, filters that are selectively permeable for certain gases only can be used if a sensor arranged downstream of the filter shall not measure corresponding gases for which the filter is not permeable. This may be especially useful if the sensor has a cross sensitivity, namely, for a first gas, which shall be detected with the sensor, on the one hand, and, on the other hand, for a second gas, which can be captured (blocked/filtered) by means of the filter and which shall not be detected with the sensor. If, however, the filter is no longer in good working order and becomes permeable for the second gas, which is actually to be captured, one speaks of a filter breakthrough. The second gas, which is in this case flowing unrecognized through the filter, can distort the measured value that is outputted by the sensor. However, such a filter breakthrough is also recognizable by means of the method according to the present invention if the first test gas and the second test gas are selected correspondingly. 
         [0073]    In a test station for carrying out the above-described method according to the present invention, the present invention makes provisions for the test station to have a main unit including a control and analysis unit, wherein the test station has a plurality of test modules, which are connected with the main unit for data exchange and into which a gas-measuring device each can be inserted, and the test station has means for recognizing the model of the device in order to detect the model of the device and/or the model of the gas sensor of the respective gas-measuring device inserted into a test module, and the main unit has a plurality of gas inlets for different test gases, and the test station has a first gas feed line, through which test gas can be sent to the test modules, a second gas feed line, through which a purging gas can be sent to the test modules, and a gas drain line, through which gas can be sent back from the test modules to the main unit, and the control and analysis unit is set up to carry out and/or control steps d. through m. of the above-described method according to the present invention. 
         [0074]    It is advantageous in this case if the control and analysis unit is set up to carry out and/or control steps B and C corresponding to the above-described method. Furthermore, it is advantageous if the gas feed line of each test module can be connected fluidically with the gas inlet of a gas-measuring device to be tested when the gas-measuring device is inserted into the test module. It is also useful if each test module has a gas drain line, which can be connected with the gas drain line of the test station. The gas feed line of at least one test module preferably has a first feed valve and a second feed valve, and this gas feed line can be connected with the first gas feed line via the first feed valve and with the second gas feed line via the second feed valve. 
         [0075]    Further features, details and advantages of the present invention appear from the text of the claims as well as from the following description of exemplary embodiments and from the figures. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0076]      FIG. 1  is a schematic view of a test station for carrying out the method according to the present invention; 
           [0077]      FIG. 2   a  is a schematic view showing a state during the course of the method for a gas-measuring device inserted into the test station; 
           [0078]      FIG. 2   b  is a schematic view showing another state during the course of the method for a gas-measuring device inserted into the test station; 
           [0079]      FIG. 2   c  is a schematic view showing another state during the course of the method for a gas-measuring device inserted into the test station; 
           [0080]      FIG. 2   d  is a schematic view showing another state during the course of the method for a gas-measuring device inserted into the test station; 
           [0081]      FIG. 2   e  is a schematic view showing another state during the course of the method for a gas-measuring device inserted into the test station; 
           [0082]      FIG. 2   f  is a schematic view showing another state during the course of the method for a gas-measuring device inserted into the test station; 
           [0083]      FIG. 3   a  is a detail showing a state during the course of the method in case of a plurality of gas-measuring devices inserted independently from one another into the test station; 
           [0084]      FIG. 3   b  is a detail showing another state during the course of the method in case of a plurality of gas-measuring devices inserted independently from one another into the test station; and 
           [0085]      FIG. 3   c  is a detail showing another state during the course of the method in case of a plurality of gas-measuring devices inserted independently from one another into the test station. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0086]    Referring to the drawings in particular, a test station  10 , which has a main unit  20  and a plurality of test modules  30 , is recognized in  FIG. 1 . The number of test modules  30  is variable. A control and analysis unit  21  is arranged in the main unit  20 . The control and analysis unit  21  is connected with an output unit  27  and with a port  26  via data exchange means  28 . The output unit  27  is likewise arranged in the main unit  20 . However, according to an alternative embodiment, the output unit  27  is a component separate from the main unit  20 . The port  26  can be connected with a plurality of gas inlets  22  arranged in the main unit  20 . A test gas P 1 , P 2 , P 3  can flow through each of the gas inlets  22 , and a separate gas inlet  22  is preferably provided for each test gas P 1 , P 2 , P 3 . The number of gas inlets  22  is variable, and the three gas inlets  22  shown in  FIG. 1  are merely exemplary. More or fewer gas inlets  22  may also be present in alternative embodiments. 
         [0087]    Port  26  is connected with a first gas feed line  23 , through which the test gas P 1 , P 2 , P 3  can flow from the main unit  20  to the test modules  30 . 
         [0088]    A furthermore, a port for a purging gas S, which is connected with a second gas feed line  24  and through which purging gas S can flow to the test modules  30 , is formed in the main unit  20 . In addition, an outlet is formed in the main unit  20  for gas A flowing back from the test modules  30 , which outlet is connected with a gas drain line  25 , through which gas A can flow back from the test modules  30  to the main unit  20 . 
         [0089]    The test modules  30  have a mount  32  each for a gas-measuring device  40 . A gas-measuring device  40  typically has a gas inlet  41  and a gas outlet  42 . Furthermore, each of the test modules  30  has a device model recognition means  50 . Furthermore, the test modules  30  are each connected with the main unit  20 , especially with the control and analysis unit  21 , via data exchange means  31 . 
         [0090]    It is recognized that the test modules  30  have a gas feed line  33  and a gas drain line  36  each. The gas feed line  33  is connected with the mount  32  such that the gas feed line  33  can be connected fluidically with the gas inlet  41  of a gas-measuring device  40  inserted into the mount  32 . The gas drain line  36  is connected with the mount  32  such that the gas drain line  36  can be connected fluidically with the gas outlet  42  of a gas-measuring device  40  inserted into the mount  32 . 
         [0091]    The gas feed line  33  has a first feed valve  34 . The first feed valve  34  can be connected with the first gas feed line  23 . The gas feed line  33  has, in addition, a second feed valve  35 . The second feed valve  35  can be connected with the second gas feed line  24 . The open or closed state of the first feed valve  34  and the second second feed valve  35  are controlled via the control and analysis unit  21  via connections from valve actuators to the control and analysis unit  21 . The gas feed line  36  can be connected with the gas drain line  25  via a port  37 . 
         [0092]    A test station  10  can be recognized in  FIG. 2   a  before a gas-measuring device to be tested was inserted into one of the test modules  30 . The first feed valves  34  connected with the first gas feed line  23  are closed. The feed valves  35  connected with the second gas feed line  24  are opened. Purging gas S can thus flow through the test modules  30 . The port  26  is in a random port position; it is connected here with the gas inlet  22 , through which the test gas P 1  can be fed. 
         [0093]    Corresponding to step a., a gas-measuring device  40  is inserted in  FIG. 2   b  into one of the test modules  30 . The gas inlet  41  of the gas-measuring device  40  is connected with the gas feed line  33 , and the gas outlet  42  is connected with the gas drain line  36 . According to step b., the device model recognition means  50  recognizes the device model of the gas-measuring device  40 , and it optionally even recognizes the gas sensor that is installed in the gas-measuring device  40 . The device model recognition means  50  transmits, corresponding to step c., the recognized information, i.e., the recognized model of the gas sensor and/or the recognized device model, to the control and analysis unit  21 . This is carried out by means of the data exchange means  31 . The first feed valve  34  continues to be closed during these steps a. through c., while the second feed valve  35  is opened, so that purging gas S flows through the gas feed line  33  into the test module  30  and consequently into the gas-measuring device  40  and back again into the gas drain line  25  through the gas outlet  42  and the gas drain line  36 . 
         [0094]    After receiving the information transmitted in step c., the control and analysis unit  21  selects, according to step d., a first test gas, which is suitable for the model of the gas sensor of the gas-measuring device  40  inserted, in this case the test gas P 3 , and connects the gas inlet  22  through which the selected test gas P 3  can be fed to the first gas feed line  23  corresponding to step e., as can be recognized in  FIG. 2   c . It is recognized in  FIG. 2   c  that the test gas P 3  will then flow through the first gas feed line  23 . 
         [0095]    According to step f., the test gas P 3  is then sent to the test module  30 , in which the gas-measuring device  40  is inserted. As can be recognized in  FIG. 2   d , the second feed valve  35  is closed and the first feed valve  34  is closed for this. The selected test gas P 3  can thus flow in this case into the test module  30  and further into the gas-measuring device  40 . The gas-measuring device  40  then outputs a first measured value m1, which is passed on to the control and analysis unit  21  via the data exchange means  31 . A first measured value m1 of the gas sensor of the gas-measuring device  40  is thus detected according to step g. 
         [0096]    After detection of the first measured value m1, it is recognized in  FIG. 2   e  that the gas-measuring device  40  is purged corresponding to step h. The first feed valve  34  is closed and the second feed valve  35  is opened for this. At the same time, the control and analysis unit  21  has already selected, according to step i., a second test gas P 1 , P 2 , P 3 , here the test gas P 1 , which is suitable for the model of the gas sensor of the gas-measuring device  40  inserted. Furthermore, the control and analysis unit  21  shown in  FIG. 2   e  has already transmitted the control command to the port  26  and has connected the first gas feed line  23  with the gas inlet  22 , through which the selected second test gas P 1  can be fed. The gas inlet  22 , through which the test gas P 1  can be fed, is already connected to the first gas feed line  23  according to step j. 
         [0097]    According to step k., the test gas P 1  is then sent to the test module  30 , in which the gas-measuring device  40  is inserted. As can be recognized in  FIG. 2   f , the second feed valve  35  is again closed for this and the first feed valve  34  is opened. The selected test gas P 1  can subsequently flow into the test module  30  and further into the gas-measuring device  40 . The gas-measuring device  40  then outputs a second measured value m2, which is passed on via the data exchange means  31  to the control and analysis unit  21 . A second measured value m2 of the gas sensor of the gas-measuring device  40  is thus detected according to step l. The control and analysis unit  21  thereupon determines, according to step m., based on the first measured value m1 detected and the second measured value m2 determined, whether a sensor poisoning is present. It is recognized in  FIG. 2   f  that the control and analysis unit  21  displays information on the result determined by means of the output unit  27 . 
         [0098]    Gas-measuring devices  40 ′,  40 ″,  40 ′″, which were inserted into the test station  10  at different times, are located in a plurality of test modules  30 ′,  30 ″,  30 ′″ in  FIG. 3   a . The gas-measuring devices  40 ′ and 40″ inserted into the test modules  30 ′ and 30″ are exposed to the test gas P 1  at the time indicated in  FIG. 3   a . The first feed valves  34 ′ and 34″ belonging to the test modules  30 ′ and 30″ are opened, while the second feed valves  35 ′ and 35″ are closed. The test gas P 1  is not selected either as the first test gas or as the second test gas for the gas-measuring device  40 ′″ inserted into the test module  30 ′″. The feed valve  34 ′″ is therefore closed at the time shown in  FIG. 3   a  and the second feed valve  35 ′″ is opened. It is recognized, furthermore, in  FIG. 3   a  that the test gas P 1  is used for the gas-measuring device  40 ′ to determine the first measured value m1 for this gas-measuring device  40 ′. By contrast, the test gas P 1  is used for the gas-measuring device  40 ″ to determine already the second measured value m2 for this gas-measuring device  40 ′. The control and analysis unit  21  can therefore already determine for the gas-measuring device  40 ″ according to step m. whether sensor poisoning is present and it sends information about this by means of the analysis unit  27 .  FIG. 3   a , therefore, shows the test station  10  at a time at which steps a. through d. and i. have been carried out independently from one another corresponding to step A of the above-described method for each of the gas-measuring devices  40 ′,  40 ″,  40 ′″ and at which it is determined, corresponding to step B of the above-described method, by means of the control and analysis unit  21  that the test modules  30 ′,  30 ″,  30 ′″ are equipped with gas-measuring devices  40 ′,  40 ″,  40 ′″. Furthermore, it is already determined at the time shown in  FIG. 3   a  according to step B which of the gas-measuring devices  40 ′,  40 ″,  40 ′″ need the same test gas P 1  as the next gas. These are the gas-measuring devices  40 ′ and 40″ in the case being shown. The gas-measuring device  40 ′ needs this test gas P 1  for carrying out step g. and the gas-measuring device  40 ″ needs this test gas P 1  for carrying out step l. 
         [0099]    The gas-measuring device  40 ′ will consequently have run through steps a. through g. at the time shown in  FIG. 3   a , the gas-measuring device  40 ′ will have run through steps a. through d. and the method is concluded for the gas-measuring device  40 ″ after step m. has been carried out. 
         [0100]    Accordingly, as is recognized in  FIG. 3   b , the gas-measuring device  40 ″ is removed from the test module  30 ″ at the next point in time. Therefore, gas-measuring devices  40 ′,  40 ′ are inserted into the test modules  30 ′ and  30 ′ only at the time shown in  FIG. 3   b . Corresponding to step B of the above-described method, this is already determined by the control and analysis unit  21 . The feed valve  34 ″ is consequently closed already corresponding to step C of the above-described method. Furthermore, it is likewise determined corresponding to step B of the above-described method that the gas-measuring devices  40 ′ and  40 ′ inserted into the test modules  30 ′ and  30 ′″ already need both the test gas P 2  as the next test gas P 1 , P 2 , P 3 . The gas inlet  22 , through which the test gas P 2  can be fed, is then connected to the first gas feed line  23 . The feed valves  34 ′ and  34 ′″ are opened, and the feed valves  35 ′ and  35 ′ are closed. The test gas P 2  therefore flows both into the gas-measuring device  40 ′ and into the gas-measuring device  40 ′. 
         [0101]    The second measured value m2 is detected in this case for the gas-measuring device  40 ′ according to step l., and it is determined by the control and analysis unit  21  according to step m. whether sensor poisoning is present, and it is recognized that the control and analysis unit  21  indicates the result of step m. by means of the output unit  27 . 
         [0102]    At the same time, the first measured value m1 is detected according to step g. for the gas-measuring device  40 ′″. 
         [0103]    The method is therefore concluded after carrying out step m. for the gas-measuring device  40 ′ at the time shown in  FIG. 3   b . The gas-measuring device  40 ′″ will have run through steps a. through g. at this point in time. 
         [0104]    The gas-measuring device  40 ′ is then removed from the test module  30 ′ at the time shown in  FIG. 3   c . The next gas-measuring device  40 ″″ may already be inserted into the test module  30 ″. Steps 1. and m. are carried out for the gas-measuring device  40 ′″ at this point in time. The first gas feed line  23  is connected in this case to the gas inlet  22 , through which the test gas P 3  can be fed. It is recognized that steps a. through m. are carried out at least once for all three gas-measuring devices  40 ′,  40 ″,  40 ′″ inserted into the test station  10  at the time shown in  FIG. 3   a , and the test station always carries out the following steps:
       A. Carrying out steps a. and d. and/or carrying out step i. for each of the gas-measuring devices  40 ′,  40 ″,  40 ′″ independently from one another;   B. Determining, by means of the control and analysis unit  21 , which of the test modules  30 ′,  30 ″,  30 ′″ are equipped with gas-measuring devices  40 ′,  40 ″,  40 ′″ and which of these gas-measuring devices  40 ′,  40 ″,  40 ′″ need the same test gas P 1 , P 2 , P 3  as the next test gas;   C. Closing the feed valve  34 ′,  34 ″,  34 ″, which is arranged between the first gas feed line  23  and the respective test module  30 ′,  30 ″,  30 ′″, for all test modules  30 ′,  30 ″,  30 ′″, which do not need the test gas P 1 , P 2 , P 3  selected in B in the next step; and   D. Carrying out steps e. through h. or steps j. through m. for each of the gas-measuring devices  40 ′,  40 ″,  40 ′″ determined in B independently from one another.       
 
         [0109]    The test gas P 1 , P 2 , P 3  may be selected from among one of the following gas mixtures in all the above-described exemplary embodiments:
       Propane;   Propane mixed with H 2 S, CO, O 2  and/or CO 2 ;   Pentane;   Pentane mixed with H 2 S, CO, O 2  and/or CO 2 ;   Butane;   Hydrogen;   Methane;   Methane mixed with H 2 S, CO, O 2  and/or CO 2 ; and   Mixtures of these gas mixtures mentioned.       
 
         [0119]    For example:
       test gas P 1  may be (2.5 vol. % CH 4 );   test gas P 2  may be (0.9 vol. % C 4 H 10 ); and   test gas P 3  may be (mixed gas containing 0.4 vol. % C 3 H 8 , 18 vol. % O 2 , 2 vol. % CO 2 , 50 ppm CO, 15 ppm H 2 S in N 2 )
 
in the example described in  FIGS. 2   a  through  2   f  as well as in the example described in  FIGS. 3   a  through  3   c.  
       
 
         [0123]    Other test gases and other concentrations are, of course, conceivable. 
         [0124]    All the features and advantages emerging from the description, claims and drawings, including design details, arrangements in space and method steps may be essential for the present invention both alone and in the different combinations. While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 APPENDIX 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 A 
                 Gas 
               
               
                 P1 
                 Test gas 
               
               
                 P2 
                 Test gas 
               
               
                 P3 
                 Test gas 
               
               
                 S 
                 Purging gas 
               
               
                 10 
                 Test station 
               
               
                 20 
                 Main unit 
               
               
                 21 
                 Control and analysis unit 
               
               
                 22 
                 Gas inlet 
               
               
                 23 
                 Gas feed line 
               
               
                 24 
                 Gas feed line 
               
               
                 25 
                 Gas feed line 
               
               
                 26 
                 Port 
               
               
                 27 
                 Output unit 
               
               
                 28 
                 Data exchange means 
               
               
                 30 
                 Test module 
               
               
                 31 
                 Data exchange means 
               
               
                 32 
                 Mount 
               
               
                 33 
                 Gas feed line 
               
               
                 34 
                 Feed valve 
               
               
                 35 
                 Feed valve 
               
               
                 36 
                 Gas drain line 
               
               
                 37 
                 Port 
               
               
                 40 
                 Gas-measuring device 
               
               
                 41 
                 Gas inlet 
               
               
                 42 
                 Gas outlet 
               
               
                 50 
                 Device model recognition means