METHOD FOR TESTING A GAS SENSOR IN A GAS-MEASURING SYSTEM

Abstract

A method for testing a gas sensor (5) is based on a gas-measuring system (1) with a test gas source (8) and with a pumping device (9). A predefined quantity of a gas or of a gas mixture is fed in, from the test gas source (8), to the gas sensor (5) over a predefined time and metered. The response of a measured signal (51) of the gas sensor is determined as a sensor response. Characteristic variables, from which an indicator of the ability of the gas sensor (5) to operate is determined, are determined from the sensor response.

Claims

1. A method for testing a gas sensor in a gas-measuring system and/or for testing the gas-measuring system, the method comprising the steps of: providing the gas-measuring system comprising the gas sensor, a control unit, a pumping device and with a test gas source; determining an indicator of readiness of the gas sensor in the gas-measuring system and/or of readiness of the gas-measuring system to operate by the control unit from sequence of the operating states including a first operating state and a sequence of additional operating states; coordinating, with the control unit, the sequence of the operating states including: continuously feeding a predefined quantity of a gas or of a gas mixture, with the pumping device, from a measuring environment to the gas sensor in the first operating state with a continuous measuring operation; reducing the quantity of gas fed by the pumping device to the gas sensor in a second operating state; activating the test gas source in a third operating state; increasing the quantity of gas fed by the pumping device to the gas sensor in the third operating state; deactivating the test gas source, after the end of the predefined time, in a fourth operating state; determining, by measurement, the gas being fed to the gas sensor by the pumping device in the fourth operating state and recoding a set of measured values over a time period; determining at least one characteristic variable from the set of measured values in the fourth operating state; determining the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system from the at least one characteristic variable in the fourth operating state; and resuming the first operating state, with continuous measuring operation with continuous feeding of the predefined quantity of gas or gas mixture from the measuring environment through the pumping device, from the fourth operating state.

2. A method in accordance with claim 1, wherein a set of messages is provided by an output unit and is generated by means of the control unit or by means of then output unit connected to the control unit, in a fifth or in an additional operating state, on a basis of the indicator of readiness of the gas sensor to operate.

3. A method in accordance with claim 1, wherein the set of measured values of the gas sensor is analyzed by the control unit in the fourth operating state and a sensor response is divided into a rise phase of the measured value, a measured value plateau phase and a fall phase of the measured value.

4. A method in accordance with claim 1, wherein a peak of an amplitude of a measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate compared to an expected or predefined desired peak amplitude as a comparison variable.

5. A method in accordance with claim 1, wherein an average amplitude of a measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system compared to an expected or predefined average desired amplitude as a comparison variable.

6. A method in accordance with claim 1, wherein a duration of rise of a sensor response of a measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate compared to an expected or predefined duration of rise of the sensor response as a comparison variable.

7. A method in accordance with claim 1, wherein a gradient of rise of a measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable for determining the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate as a change in an amplitude of the measured value as a function of the time difference compared to an expected or predefined desired gradient of rise desired as a comparison variable.

8. A method in accordance with claim 1, wherein an integral of an amplitude of a measured signal of a sensor response of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate compared to an expected or predefined measured signal integral as a comparison variable.

9. A method in accordance with claim 1, wherein a duration of a sensor response of the measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable for determining the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate compared to an activation time of the test gas source as a comparison variable.

10. A method in accordance with claim 1, wherein in the fourth operating state the control unit analyses at least any two of: a peak of an amplitude of a measured signal of the gas sensor compared to an expected or predefined desired peak amplitude as a comparison variable; an average amplitude of a measured signal of the gas sensor compared to an expected or predefined average desired amplitude as a comparison variable; a duration of rise of a sensor response of a measured signal of the gas sensor compared to an expected or predefined duration of rise of the sensor response as a comparison variable; a gradient of rise of a measured signal of the gas sensor as a change in an amplitude of the measured value as a function of the time difference compared to an expected or predefined desired gradient of rise desired as a comparison variable; an integral of an amplitude of a measured signal of a sensor response of the gas sensor; and a duration of a sensor response of the measured signal of the gas sensor compared to an activation time of the test gas source as a comparison variable, as a characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate.

11. A gas-measuring system comprising: a gas sensor; a pumping device; a test gas source; and a control unit determining an indicator of readiness of the gas sensor and/or of readiness of the gas-measuring system to operate, the control unit coordinating a sequence of operating states comprising: controlling a continuous feeding of a predefined quantity of a gas or of a gas mixture, with the pumping device, from a measuring environment to the gas sensor in the first operating state with a continuous measuring operation; reducing the quantity of gas fed by the pumping device to the gas sensor in a second operating state; activating the test gas source in a third operating state; increasing the quantity of gas fed by the pumping device to the gas sensor in the third operating state; deactivating the test gas source, after the end of the predefined time, in a fourth operating state; determining, by measurement, the gas being fed to the gas sensor by the pumping device in the fourth operating state and recoding a set of measured values over a time period; determining at least one characteristic variable from the set of measured values in the fourth operating state; determining the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system from the at least one characteristic variable in the fourth operating state; and resuming the first operating state, with continuous measuring operation with continuous feeding of the predefined quantity of gas or gas mixture from the measuring environment through the pumping device from the fourth operating state.

12. A gas-measuring system in accordance with claim 11, further comprising an output unit connected to the control unit, wherein a set of messages is provided by the output unit and is generated by the control unit or by the output unit connected to the control unit, in a fifth or in an additional operating state, on a basis of the indicator of readiness of the gas sensor to operate.

13. A gas-measuring system in accordance with claim 11, wherein the set of measured values of the gas sensor is analyzed by the control unit in the fourth operating state and a sensor response is divided into a rise phase of the measured value, a measured value plateau phase and a fall phase of the measured value.

14. A gas-measuring system in accordance with claim 11, wherein a peak of an amplitude of a measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate compared to an expected or predefined desired peak amplitude as a comparison variable.

15. A gas-measuring system in accordance with claim 11, wherein an average amplitude of a measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system compared to an expected or predefined average desired amplitude as a comparison variable.

16. A gas-measuring system in accordance with claim 11, wherein a duration of rise of a sensor response of a measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate compared to an expected or predefined duration of rise of the sensor response as a comparison variable.

17. A gas-measuring system in accordance with claim 11, wherein a gradient of rise of a measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable for determining the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate as a change in an amplitude of the measured value as a function of the time difference compared to an expected or predefined desired gradient of rise desired as a comparison variable.

18. A gas-measuring system in accordance with claim 11, wherein an integral of an amplitude of a measured signal of a sensor response of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate compared to an expected or predefined measured signal integral as a comparison variable.

19. A gas-measuring system in accordance with claim 11, wherein a duration of a sensor response of the measured signal of the gas sensor is analyzed by the control unit in the fourth operating state as at least one characteristic variable for determining the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate compared to an activation time of the test gas source as a comparison variable.

20. A gas-measuring system in accordance with claim 11, wherein in the fourth operating state the control unit analyses at least any two of: a peak of an amplitude of a measured signal of the gas sensor compared to an expected or predefined desired peak amplitude as a comparison variable; an average amplitude of a measured signal of the gas sensor compared to an expected or predefined average desired amplitude as a comparison variable; a duration of rise of a sensor response of a measured signal of the gas sensor compared to an expected or predefined duration of rise of the sensor response as a comparison variable; a gradient of rise of a measured signal of the gas sensor as a change in an amplitude of the measured value as a function of the time difference compared to an expected or predefined desired gradient of rise desired as a comparison variable; an integral of an amplitude of a measured signal of a sensor response of the gas sensor; and a duration of a sensor response of the measured signal of the gas sensor compared to an activation time of the test gas source as a comparison variable, as a characteristic variable to determine the indicator of readiness of the gas sensor in the gas-measuring system and/or of the gas-measuring system to operate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In the drawings:

[0070] FIG. 1 is a schematically simplified view showing a pumping device with a test gas source and with a gas sensor in a gas-measuring system; and

[0071] FIG. 2 is a view showing a schematic course of a method for testing a gas sensor with a pumping device and with a test gas source in a gas-measuring system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0072] Referring to the drawings, in a schematically simplified view, FIG. 1 shows a gas-measuring system 1 with a pumping device 9, with a test gas source 8 and with a gas sensor 5. A control unit 910 is provided with a memory 920. The control unit 910, generally and in principle, shown as a separate unit in this configuration according to FIG. 1, provides the cooperation with the pumping device 9 and with the gas generator 5. For example, an arrangement in/at the gas sensor 5, in/at the pumping device 9 or in/at a control and analysis system, not shown in this FIG. 1, represent variants of the arrangement of the control unit 910. The control unit 910, comprised of a processor unit (P, C), is configured, in conjunction with the memory 920, to implement a procedure 100 (schematically represented in FIG. 2) for testing the gas sensor 5. Further details, related to design, which are necessary for feeding quantities of gas into the gas sensor, for example, gas inlet membrane, flame protection unit, are not shown in this view in FIG. 1 for reasons of clarity.

[0073] Electronic components, power supply elements, as well as design details concerning the gas-carrying components, for example, pump, pump motor, valves, temperature, pressure and/or flow sensor systems, are not shown in this schematic view in this FIG. 1 for reasons of clarity.

[0074] The details of the configuration of the test gas source 8 with means for activation/deactivation, the species and type of the test gas, the configuration as a gas generator with electrical activation or embodiment variants in the form of a tank-type container in combination with valves, switching means, as well as sensor systems (pressure, temperature, flow) as well as design details of the manner in which the test gases are generated, provided and metered are necessary, are not shown in this schematic view in FIG. 1 for reasons of clarity.

[0075] A gas feed system 901, which is shown only schematically in this FIG. 1, connects the test gas source 8, the gas sensor 5 and the pumping device 9 with one another in such a manner that gas or air can optionally be fed from a measuring environment 39 or from the test gas source 8 to the gas sensor 5 by means of the pumping device 9. The control unit 910 controls both the test gas source 8 with activation signals 703, 704, 81 and the pumping device 9 with flow rate control signals 601, 602, 603, 91. In addition, the control unit 910 receives measured signals, time curves of measured signals 51 from the gas sensor 5 as data. An output unit 930, which is configured to display the course 100 (FIG. 2) of the method for testing a gas sensor 5, to display states of the pumping device 9, of the control unit 910, of the test gas source 8 and of the gas sensor, and is also configured to display measured signals, time curves of measured signals 51 of the gas sensor 5 in the form of at least one output signal 88, is optionally connected to the control unit 910.

[0076] A data interface 931 configured for the supply 933 of the output signal in the data exchange is optionally connected to this output unit 930.

[0077] The pumping device 9 shown in this FIG. 1 with test gas source 8 and with gas sensor 5 is used as an example for embodiment variants and combination possibilities of how such a control unit 910, memory 920, test gas source 8, gas feed system 901, pumping device 9 and gas sensor 5 can be arranged with one another and in relation to one another in series in the gas feed system 901 in order to carry out the method (FIG. 2) for testing the gas sensor 5 in the gas-measuring system 1. Embodiments in which the pumping device 9 is configured as a part of the gas sensor 5 are covered by the inventive idea of testing the gas sensor 5 in the gas-measuring system just as much as are embodiments in which components, such as the memory 920, control unit 910, output unit 930, data output unit 931 are arranged as parts of the gas-measuring system in relation to one another or with one another and cooperate to carry out the method (FIG. 2) for testing the gas sensor 5 in the gas-measuring system.

[0078] In addition, the gas feed system 901 may have components in the interior of the pumping device 9, test gas source 8, from or to the gas sensor 5, from the pumping device 9 or from the test gas source 8, as well as feed lines outside the pumping device 9, the test gas source 8 for establishing gas-carrying connections in the gas-measuring system 1. The output unit 930 can provide the result of the testing of the gas-measuring system 1 by means of the optional data interface 931 to the outside in different ways. The data interface 931 may be configured for supply 933 for an optical data transmission (IrDa), for wireless data transmission (WLAN, Bluetooth), and for wired data transmission (Ethernet, LAN, USB, industrial communication bus). Supply 933 is possible, for example, on a mobile memory 932 (memory stick, e.g., CF card, SD card, diskette, USB stick, external hard drive), a supply 933 into a central or non-central data network (LAN, WLAN), preferably configured as a data bank 934, or supply 933 to a central or non-central analysis system 935 in an industrial automation environment is possible as well.

[0079] It is possible in this way to make available the results of the testing of the gas-measuring system 1 in order to make it possible to organize maintenance or repair procedures centrally or non-centrally. The output unit 930 may also be configured in this case as a separate mobile unit, by means of which the results of the testing of the gas sensors 5 or of the gas-measuring system 1 can be collected by the maintenance personnel in a mobile form and subsequently made available for a central analysis system, for example, as a data transfer (upload) by means of a data-reading device and a personal PC.

[0080] FIG. 2 schematically shows a procedure 100 of the method with a start 60 and with an end 66 and with a sequence of steps 61, 62, 63, 64, 65 for testing a gas sensor 5 in a gas-measuring system 1 (FIG. 1) with a control unit 910 and with a memory 920. Identical components in FIG. 1 and FIG. 2 are designated in FIG. 2 by the same reference numbers as in FIG. 1. The control unit 910 comprising e.g., as a processor unit (P, C), is configured to, in conjunction with the memory 920, to implement the schematic procedure 100. The schematic procedure 100 starts after a start 60 from a first operating state 61 (step 1) with a continuous measuring operation, in which the pumping device 9 is prompted by means of a first flow rate control signal V1 601 to continuously feed a defined quantity or a defined volume of gas from the measuring environment 39 to the gas sensor 5 via a gas feed line system 901.

[0081] In a second operating state 62 (step 2) following the first operating state 61, the pumping device 9 is prompted via a second flow rate control signal V0 602 to reduce the quantity of gas being fed to the gas sensor 5. The quantity of gas is preferably reduced to such an extent that a state without movement of gas or gas supply develops at the gas sensor 5 and the gas sensor thus sends, a measured signal 51 that is used as a type of zero value as a reference point for further and subsequent measurements in the procedure 100 and this measured signal 51 is stored in the memory 920 by means of the control unit 910.

[0082] In a third operating state 63 (step 3) following the second operating state 62, the test gas source 8 is activated via an activation signal 703 to release a test gas, and the pumping device 9 is promoted at the same time or subsequently via a third flow rate control signal V3 603 to increase the quantity of gas being fed to the gas sensor 5 to a predefined quantity, so that a test gas generated or provided by the test gas source 8 is thus fed to the gas sensor 5. In a fourth operating state 64 (step 4) following the third operating state 63, the release of the test gas from the test gas source 8 is deactivated by means of a deactivation signal 704. The gas being fed to the gas sensor 5 in the fourth operating state 64 is detected by the control unit 910 by measurement and recorded as a set of measured values or measured signals over a time course. Furthermore, at least one characteristic variable 641 is determined from the set of measured values in the fourth operating state 64, and an indicator 642 for the readiness of the gas sensor 5 to operate in the gas-measuring system 1 (FIG. 1) and/or of the gas-measuring system (FIG. 1) is determined and provided from the at least one characteristic variable 641. The first operating state 61 with continuous measuring operation with continuous feeding of the predefined quantity of gas from the measuring environment 39 through the pumping device 9 to the gas sensor 5 is subsequently resumed again from the fourth operating state 64.

[0083] Three time curves are schematically shown at the left edge of FIG. 2:

[0084] An amplitude A 50 of the measured signal 51 of the gas sensor 5 over the course of time t 30,

[0085] an amplitude 80 of the activation signal 81 of the test gas source 8 over the course of time t 30, and

[0086] an amplitude 90 of the flow rate of the pumping device 9 over the course of time t 30.

[0087] These three time curves 50, 80, 90 show, each synchronized with one another in time, the time curve of the flow rate of the pumping device 9, of the activation of the test gas source 8 and the resulting response in the measured signal of the gas sensor 5 as a so-called sensor response to the influence and control 601, 602, 603, 703, 704 of the pumping device 9 and test gas source 8 by the control unit 910.

[0088] Characteristic variables arise during the so-called sensor response, for example,

[0089] during a phase of rise time 511 of the measured signal from the zero value of the measured signal 51 of the gas sensor 5 until a built-up, approximately stable peak of the measured signal is reached immediately following the activation 703 of the test gas source 8,

[0090] during a phase 512 (plateau phase) with built-up, approximately stable peak of the measured signal, and

[0091] during a phase 513 of a fall time of the measured signal from the built-up, approximately stable measured signal (phase 512) to the zero value of the measured signal 51 of the gas sensor 5 following the deactivation 704 of the test gas source.

[0092] The list of the characteristic variables 641, from which, for example, the indicator 642 of the readiness of the gas sensor 5 to operate can be determined, and Table 1 with the corresponding explanations to the sensor response are referred to here. Possible responses to the activation of the test gas source 8, characteristic variables 641 belonging to the three phases 511, 512, 513, the gradient of rise (A/t) of the measured signal 51 of the gas sensor 5, the peak of the amplitude A.sub.peak of the measured signal 51 of the gas sensor 5, the average amplitude A.sub.average of the measured signal 51 of the gas sensor 5, the duration of rise of the sensor response t.sub.rice of the measured signal 51 of the gas sensor 45, and the integral of the sensor response t.sub.response of the measured signal 51 of the gas sensor 5 can be found in this Table 1.

[0093] The determination of the indicator 642 of the readiness of the gas sensor 5 to operate in the fourth operating state 64 (step 4) is preferably carried out on the basis of a comparison with comparison variables 466, as they are likewise listed in Table 1.

[0094] Another possibility of determining the indicator 642 of the readiness of the gas sensor 5 to operate in the fourth operating mode 64 (step 4) arises in a combined analysis of the different measured variables and/or characteristic variables: The gradient of rise (A/t) of the measured signal 51 of the gas sensor 5, the peak of the amplitude A.sub.peak of the measured signal 51 of the gas sensor 5, the average amplitude A.sub.average of the measured signal 51 of the gas sensor 5, the duration of rise of the sensor response t.sub.rise of the measured signal 51 of the gas sensor 5, the integral A(t) dt of the amplitude of the measured signal 51 of the gas sensor 5, the duration of the sensor response t.sub.response of the measured signal 51 of the gas sensor 5 by the control unit 910.

[0095] Another possibility for determining the indicator 642 of the readiness of the gas sensor 5 to operate in the fourth operating state 64 (step 4) is for the control unit 910 to perform certain maneuvers when controlling the pumping device 9, for example, for the test gas source 8 to delay the release of the test gas in the third operating state 63 (step 3) or to activate it with different feed rates, so that different working points of the flow rate can be reached by the pumping device 9 by means of the control unit 910, which makes possible a differentiated diagnosis for determining the indicator 642 of the readiness of the gas sensor 5 to operate. Such maneuvers may also be carried out in programmed cycles. The maneuvers pertain to the pneumatic system and switch the pump in the pumping device 9 to other working points with changed volume flow. A response of the pressure and/or flow sensor system usually necessary for the operation of the pumping device 9 and optionally the response of the gas sensor 5 to the changed volume flow provide information for the correct performance of the maneuver compared to a stored desired response.

[0096] An example of such a maneuver is a short-term stop of the pump in the pumping device 9, initiated by the control unit 910. A time constant of the pneumatic system 901 can be determined, a feed volume can be estimated and, by means of a previously determined reference volume stored in the memory 920 (FIG. 1), the location of a leak can be estimated with such a stop maneuver by the control unit 910 from the sensor response.

[0097] The indicator 642 of the readiness of the gas sensor 5 to operate can be outputted in an optional, fifth operating state 65 (step 5) of the method in procedure 100 as an output value 88 by means of an output unit 930 (FIG. 1), not shown in this FIG. 2.

[0098] 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.

APPENDIX

List of Reference Numbers

[0099] 1 Gas-measuring system [0100] 5 Gas sensor [0101] 8 Test gas source [0102] 9 Pumping device [0103] 30 Time t, x axis [0104] 39 Environment, measuring environment (air) [0105] 50 Amplitude A of the measured signal of the gas sensor 5, y axis [0106] 51 Time curve of the measured signal of the gas sensor 5 [0107] 60 START [0108] 61 First operating state/step 1 [0109] 62 Second operating state/step 2 [0110] 63 Third operating state/step 3 [0111] 64 Fourth operating state/step 4 [0112] 65 Fifth operating state/step 5 [0113] 66 STOP [0114] 80 Activation signal of the test gas source 8, y axis [0115] 81 Time curve of the activation signal of the test gas source 8 [0116] 88 Output value [0117] 90 Flow rate of the pumping device 9, y axis [0118] 91 Time curve of the flow rate of the pumping device 9 [0119] 511 Phase of rise time [0120] 512 Phase with stable measured signal (plateau) [0121] 513 Fall phase time [0122] 601 First flow rate control signal V1 [0123] 602 Second flow rate control signal V0 [0124] 603 Third flow rate control signal V3 [0125] 641 Characteristic variable [0126] 642 Indicator of readiness of the gas sensor 5 to operate [0127] 703 Activation signal for the test gas source [0128] 704 Deactivation signal for the test gas source [0129] 901 Gas feed line system [0130] 910 Control unit [0131] 920 Memory [0132] 930 Output unit [0133] 931 Data interface [0134] 932 Mobile memory [0135] 933 Supply as a data signal [0136] 934 Data bank [0137] 935 Analysis system