Sensor and sensor system

Abstract

The invention relates to a sensor for determining two measured variables of a gas. The sensor has at least a first sensor element and a second sensor element and two control connections. The first sensing element and the second sensing element are connected in series. The sensor element is arranged between the actuation connections. The first sensing element is provided with a first electronic equivalent circuit diagram, and the first electronic equivalent circuit diagram comprises a parallel circuit composed of a first resistor and a first capacitor. The second sensing element is provided with a second electronic equivalent circuit diagram, and the second electronic equivalent circuit diagram comprises a second capacitor.

Description

TECHNICAL FIELD

[0001] The present application relates to a sensor, to a sensor system, to a method for operating a sensor and to an evaluation electronics for reading a sensor. BACKGROUND

[0002] From the prior art, gas sensor modules are known in which the resistance of a gas sensor chip and the capacitance of a humidity sensor are measured via separate signal inputs of an evaluation electronics, for example a sensor ASIC. Here, the gas sensor chip and the humidity sensor are connected to the evaluation electronics by means of separate bond wires. Furthermore, a pressure sensor, which can be, for example, a piezoresistive pressure sensor or a capacitive pressure sensor, can be included in the gas sensor module and likewise connected to the evaluation electronics via separate bond wires. In particular, a capacitive pressure sensor can be implemented simply and can be integrated into an existing chip geometry. It can be provided, in particular, that the gas sensor module has a semiconductor chip, wherein the semiconductor chip contains both the gas sensor or the plurality of gas sensors and the humidity sensor and, if necessary, also the pressure sensor. SUMMARY

[0003] It is an object of the present application to provide an improved sensor, for example configured as a gas sensor module. It is a further object of the present application to provide an improved sensor system having such a sensor, an improved method for operating the sensor and an improved evaluation electronics for reading the sensor. These objects are solved by the subject matter of the independent claims. Advantageous extensions are given in the dependent claims.

[0004] According to a first aspect, the present application relates to a sensor for determining two measurement variables of a gas. Here, the gas can also be referred to as an atmosphere. The sensor has at least a first and a second sensor element and two actuation connections. The first and the second sensor element are connected in series. The sensor elements are arranged between the actuation connections. The first sensor element has a first electrical equivalent circuit diagram, wherein the first electrical equivalent circuit diagram comprises a parallel circuit consisting of a first resistance and a first capacitance. The second sensor element has a second electrical equivalent circuit diagram, wherein the second electrical equivalent circuit diagram comprises a second capacitance.

[0005] Here, the measurement variables can comprise, in particular, the identification of a gas class. Furthermore, the measurement variables can comprise the concentration of a specific gas, the pressure and / or the humidity.

[0006] The sensor may also have a heating element that is in thermal contact with the first sensing element. Alternatively or additionally, the sensor may have a further heating element that is in thermal contact with the second sensing element. Furthermore, a heating element control connection may be provided, which allows control of the heating element and / or the further heating element.

[0007] In particular, no additional control connection is provided between the sensing elements, specifically between the first and second sensing elements. Therefore, the electronic signal introduced via one of the control connections passes through the first and second sensing elements and then through the other control connection. Thus, the two sensing elements become accessible in a common measurement via a shared control connection. This eliminates or shortens the single wire between the sensing elements and the analysis and processing unit.

[0008] To read the first and second sensing elements, the asymmetry between the first sensing element, which has a first resistor and a first capacitor connected in parallel, and the second sensing element, which has a second capacitor, can be utilized to reconstruct the characteristics of the two sensing elements.

[0009] Here, the first and second sensing elements can be configured as individual components and interconnected. The first sensing element may particularly include a gas sensor, which can be used to determine the type of gas. It is typically necessary to determine the resistance and capacitance of the first material used in the first sensing element. This can be done through a parallel circuit consisting of the first resistor and the first capacitor, as shown in the first equivalent circuit diagram. The second sensing element can then be a humidity sensor or a pressure sensor, wherein the capacitance of the second material is analyzed as a second capacitance to determine humidity or pressure. Alternatively, a third sensing element can be connected in series in addition to the second sensing element; the third equivalent circuit diagram includes a third capacitor; and here, the humidity sensor is configured as the second or third sensing element, and the pressure sensor as the third or second sensing element. The second sensing element can also include a gas sensor, which can also be used to determine the type of gas. The first and second sensing elements can then be different to determine different types of gas.

[0010] According to a second aspect, the application relates to an evaluation unit having a computing unit and at least two connection terminals. The connection terminals can be connected to the actuation connection terminals of a sensor according to the application. The evaluation unit is configured to excite the sensor via the connection terminals at a predefinable frequency, to determine a complex impedance, and to calculate the two measured variables from the complex impedance. The complex impedance can then comprise a magnitude and a phase, wherein the two measured variables are calculated from the magnitude and the phase of the complex impedance. Alternatively to the magnitude and the phase, the evaluation can also take place via the real part and the imaginary part of the complex impedance. With this evaluation unit, a sensor having an asymmetry in the circuit composed of the first sensor element and the second sensor element, as explained in the first aspect, can be read, in particular, and the properties of the two sensor elements can be reconstructed here.

[0011] The evaluation unit can have, in particular, an integrated circuit (IC), preferably an application-specific integrated circuit (ASIC). Alternatively, the evaluation unit can also comprise a microcontroller.

[0012] The evaluation unit can have a heating signal output connection terminal, which can be connected to the heating element actuation connection terminal.

[0013] According to a third aspect, the application relates to a sensor system having a sensor according to the application and an evaluation unit according to the application. In particular, the sensor and the evaluation unit can be arranged inside a common housing.

[0014] According to a fourth aspect, the application relates to a method for operating a sensor according to the application, in which method the sensor is first excited at a predefinable frequency. Subsequently, a complex impedance is determined. Next, two measured variables are calculated from the complex impedance. The complex impedance can then comprise a magnitude and a phase, wherein the two measured variables are calculated from the magnitude and the phase of the complex impedance. Alternatively to the magnitude and the phase, the evaluation can also take place via the real part and the imaginary part of the complex impedance. With this method, a sensor having an asymmetry in the circuit composed of the first sensor element and the second sensor element, as explained in the first aspect, can be read, in particular, and the properties of the two sensor elements can be reconstructed here.

[0015] In one embodiment of the sensor, the first sensor element and the second sensor element are arranged on a common sensor chip. Here, the electrical connection of the two sensor elements can also be realized on the sensor chip, so that a serial connection of the two sensor elements according to the application is automatically derived. This makes it possible to provide a smaller sensor, if necessary.

[0016] In one embodiment of the sensor, the second electronic equivalent circuit diagram of the second sensing element includes a second resistor. The second electronic equivalent circuit diagram includes a parallel circuit consisting of the second resistor and the second capacitor. Other sensing methods can also be employed accordingly. Furthermore, a third sensing element, if necessary, can also be provided, and in this third electronic equivalent circuit diagram, it also has a third resistor.

[0017] In one embodiment of the sensor, the first sensing element has a bridging resistor. The bridging resistor is arranged in parallel with a parallel circuit consisting of a first resistor and a first capacitor. Under certain operating conditions, this can improve reading accuracy or make reading possible.

[0018] In one embodiment of the sensor, the second sensing element has a bridging capacitor. The bridging capacitor is arranged in parallel with the second capacitor. Under certain operating conditions, this can improve reading accuracy or make reading possible.

[0019] In one embodiment of the sensor, the sensor has an additional first sensing element and an additional second sensing element. The additional first sensing element may structurally correspond to the first sensing element. The additional second sensing element may structurally correspond to the second sensing element. Here, the additional first sensing element and the additional second sensing element are also connected in series and via an additional control connection terminal. The additional control connection terminal may be connected to another connection terminal of the analysis and processing unit.

[0020] In one embodiment of the analysis and processing unit, the unit is configured to: excite the sensor at a plurality of predefined frequencies via the connection terminal, determine an extreme frequency, and determine the two measurement parameters by the complex impedance at and from the extreme frequency. The complex impedance may include magnitude and phase, wherein the two measurement parameters are calculated from the magnitude and phase of the complex impedance. Alternatively, analysis and processing can be performed via the real and imaginary parts of the complex impedance. Here, the extreme frequency can be assigned to the maximum value of the phase of the complex impedance, wherein the maximum value may have a negative sign, and the magnitude of the maximum value then corresponds to the minimum value. This enables simple reading of a sensor having a parallel circuit consisting of a first resistor and a first capacitor, and a series circuit consisting of a second capacitor.

[0021] In one embodiment of the analysis and processing unit, the unit is configured to: excite sensors at multiple frequencies via a connection terminal, and determine more than two measurement parameters based on the magnitude and phase of the complex impedance at said frequencies. This can be advantageous, especially if more than two sensing elements are provided, and if the second sensing element includes a second resistor. Attached Figure Description

[0022] Embodiments of the present invention will be illustrated with reference to the following drawings. As shown in the schematic diagrams: Figure 1 A sensor system with sensors and analysis and processing units; Figure 2 Equivalent circuit diagram of the sensor; Figure 3 Impedance spectrum; Figure 4 Another sensor system; Figure 5 A flowchart of another method for operating another sensor; and Figure 6 Equivalent circuit diagram of another sensor. Detailed Implementation

[0023] Figure 1 A sensor system 1 with a sensor 10 and an analysis and processing unit 80 is shown. The sensor 10 is adapted to determine two measurement parameters of a gas and has at least one first sensing element 11 and a second sensing element 12, as well as two control connection terminals 17. The first sensing element 11 and the second sensing element 12 are connected in series. The sensing elements 11 and 12 are arranged between the control connection terminals 17. The analysis and processing unit 80 has a calculation unit 81 and at least two connection terminals 82. The control connection terminals 17 can be connected to the connection terminals 82 via a connection portion 2, wherein the connection portion 2 may be arranged outside the sensor system 1 (solid line) or alternatively inside the sensor system 1 (dashed line).

[0024] In particular, no additional control connection is provided between sensing elements 11 and 12, i.e., between the first sensing element 11 and the second sensing element 12. Therefore, the electronic signal introduced via one of the control connection terminals 17 passes through the first sensing element 11 and the second sensing element 12 and then through the other control connection terminal 17. Thus, the two sensing elements 11 and 12 become accessible in a common measurement via the common control connection terminal 17. This eliminates or shortens the single wire between the sensing elements 11 and 12 and the analysis and processing unit 80. The first sensing element 11 may have a first material 14. The second sensing element 12 may have a second material 15. For a particular sensor type (e.g., a pressure sensor), 15 may also have a more extensive measurement unit, such as a diaphragm with mechanical coupling to a cavity. The first material 14 may be a first sensing material. The second material 15 may be a second sensing material.

[0025] Here, the first sensing element 11 and the second sensing element 12 can each be configured as a single component and interconnected. The first sensing element 11 may include, in particular, a gas sensor, which can be used to determine the type of gas. Here, it is generally necessary to determine the resistance and capacitance of the first material 14 used for the first sensing element 11. The second sensing element 12 can then be a humidity sensor or a pressure sensor, in which the capacitance of the second material 15 is read. It is also possible to configure a third sensing element (not shown here) in series with the second sensing element 12; and here the humidity sensor is configured as the second sensing element 12 and the pressure sensor as the third sensing element, or vice versa. However, the second sensing element 12 may also include another gas sensor, which can be used to determine the type of another gas.

[0026] The analysis and processing unit 80 is configured to: excite the sensor 10 at a predefined frequency via the connection terminal 82, determine the complex impedance, and calculate the two measurement parameters from the complex impedance. The complex impedance may then include magnitude and phase, wherein the two measurement parameters are calculated from the magnitude and phase of the complex impedance. Alternatively, analysis and processing can be performed via the real and imaginary parts of the complex impedance. Here, the analysis and processing unit 80 and the sensor 10 may be arranged in a common housing 3. Alternatively, the analysis and processing unit 80 and the sensor 10 may be arranged in different housings or components. These method steps can also be performed for multiple predefined frequencies, for example, within a frequency scanning framework.

[0027] Here, the analysis and processing unit 80 may particularly have an integrated circuit (IC), preferably an application-specific integrated circuit (ASIC). Alternatively, the analysis and processing unit 80 may also include a microcontroller. This can be implemented separately within the computing unit 81.

[0028] Figure 2 It shows Figure 1 The electronic equivalent circuit diagram of sensor 10 is shown in Figure 20.

[0029] The first sensing element 11 has a first electronic equivalent circuit diagram 21. The second sensing element 12 has a second electronic equivalent circuit diagram 22. The first electronic equivalent circuit diagram 21 includes a parallel circuit consisting of a first resistor 23 and a first capacitor 24. The second electronic equivalent circuit diagram 22 includes a second capacitor 25.

[0030] To determine the resistance and capacitance of the first material 14, the readings of the first sensing element 11 can be performed via a parallel circuit consisting of the first resistor 23 and the first capacitor 24, as described with respect to the first electronic equivalent circuit diagram 21. The readings of the second sensing element 12 can be performed via the second capacitor 25, as described with respect to the second electronic equivalent circuit diagram 22, to determine humidity or pressure.

[0031] To read the first sensing element 11 and the second sensing element 12, the asymmetry between the first sensing element 11, which has a first resistor 23 and a first capacitor 24 connected in parallel, and the second sensing element 12, which has a second capacitor 25, can be utilized to reconstruct the characteristics of the two sensing elements 11 and 12. Here, using the analysis processing unit 80, the characteristics of the sensing elements 11 and 12 can be read in particular. Figure 2 The related explanation describes the asymmetry of the sensor 10 in the circuit composed of the first sensing element 11 and the second sensing element 12, and here the characteristics of the two sensing elements 11 and 12 can be reconstructed.

[0032] Figure 3 Impedance spectrum 100 is shown, in which phase 102 with phase direction 103 is plotted based on frequency 101, and impedance magnitude 104 with impedance direction 105 is plotted. Impedance spectrum 100 can be determined theoretically or experimentally for sensor 10. There can be an extreme frequency 106 in impedance spectrum 100, at which phase 102 has a maximum value, which can be called phase maximum value 107. Here, phase 102 can be plotted entirely in the negative region, so that considering the negative sign, phase maximum value 107 is a minimum value. Impedance magnitude 104 can also be determined for extreme frequency 106, which can be called extreme frequency magnitude 108. Using extreme frequency 106, phase maximum value 107, and extreme frequency magnitude 108, the first resistor 23, the first capacitor 24, and the second capacitor 25 can then be reconstructed using the stored characteristic plot. Intermediate storage of more measurements can be performed, however, these measurements are primarily necessary to find extreme frequency 106. However, once the extreme frequency 106 is identified, all other measurements at other frequencies can be discarded. This achieves an efficient method for reading sensor 10.

[0033] It can be configured so that measurements taken at other frequencies are not discarded but are used to determine the measurement parameters. This allows for more accurate measurements.

[0034] In one embodiment of sensor 10, such as in Figure 1As shown, the first sensing element 11 and the second sensing element 12 are arranged on a common sensor chip 18. However, alternatively, the first sensing element 11 and the second sensing element 12 may be arranged on their respective sensor chips.

[0035] In some cases, the gaseous environment present during measurement may introduce the first resistor 23, the first capacitor 24, and / or the second capacitor 25 into an unfavorable measurement range. These can be eliminated through modification, thus eliminating the disadvantages compared to measurements using two separate sensing elements.

[0036] In one embodiment of sensor 10, the first sensing element 11 has a bridging resistor 26, such as Figure 2 As shown. The bridging resistor 26 is arranged in parallel with the parallel circuit consisting of the first resistor 23 and the first capacitor 24, with the connecting wires shown as dashed lines to illustrate that the bridging resistor 26 is not necessary in all configurations. The bridging resistor 26 may be advantageous, especially when the impedance of the first resistor 23 relative to the first capacitor 24 is large at the extreme frequency 106. In this case, the current supplied by the control connection 17 will flow essentially, or if necessary, even only through the first capacitor 24 in the first sensing element 11. Therefore, the two sensing elements 11, 12 will effectively be two capacitors 24, 25 connected in series, which, as an electronic equivalent circuit diagram, will again correspond to a single capacitor. Distinction will no longer be possible. The bridging resistor 26 allows at least the first capacitor 24 and the second capacitor 25 to be distinguished again.

[0037] Even when the first sensing element 11 is completely turned off, that is, when the impedance of the first resistor 23 and the first capacitor 24 becomes similar to or greater than the measurement range of the analysis and processing unit 80, the second capacitor 25 can still be determined by means of the bridging resistor 26.

[0038] If the first resistance 23 becomes very small due to the gas being measured, especially smaller than the impedance of the first capacitor 24 at its extreme frequency of 106, then the current essentially flows around the first capacitor 24 and can no longer be measured. This drawback also exists in a single sensing element. Measurement of the first resistance 23 and the second capacitor 25 is still possible.

[0039] In one embodiment of sensor 10, the second sensing element 12 has a bridging capacitor 27, such as Figure 2As shown, bridging capacitor 27 is arranged in parallel with second capacitor 25, with the connecting wires shown as dashed lines to illustrate that bridging capacitor 27 is not necessary in all configurations. If the second capacitor 25 becomes so small due to the gas being measured that its impedance at the extreme frequency 106 becomes equal to or greater than the measurement range of the impedance of analysis processing unit 80, then a cutoff mechanism exists. At that point, first resistor 23 and first capacitor 24 can no longer be measured. Through bridging capacitor 27, first resistor 23 and first capacitor 24 become measurable again.

[0040] The bridging resistor 26 and / or bridging capacitor 27 can be placed outside the sensing elements 11 and 12. However, the bridging resistor 26 and / or bridging capacitor 27 can also be integrated on the chip of the sensing elements 11 and 12 or on the common chip 18.

[0041] Figure 4 Another embodiment of the sensor system 1 is shown, in which the sensor 10 is connected to the analysis and processing unit 80, as in combination Figure 1 The electronic equivalent circuit diagram 20 is explained and is equivalent to Figure 2 Here, the values ​​of capacitance and resistance are not necessarily equal; "equivalent" refers to the circuit arrangement. Furthermore, sensor system 1 has another sensor 30, which includes another first sensing element 31 and another second sensing element 32. The additional first sensing element 31 and the additional second sensing element 32 are connected in series and, similar to sensor 10, are connected to another connection terminal 83 of the analysis and processing unit via another analysis and processing connection terminal 37. Another electronic equivalent circuit diagram 40 of the additional sensor 30 is equivalent to the electronic equivalent circuit diagram 20 of sensor 10, such that the additional first sensing element 31 includes another first electronic equivalent circuit diagram 41 having a parallel circuit composed of another first resistor 43 and another first capacitor 44, and the additional second sensing element 32 includes another second electronic equivalent circuit diagram 42 having another second capacitor 45. This additional sensor 30 can then be read similarly to sensor 10.

[0042] In Figure 2 The components described in the relevant explanation, such as bridging resistor 26 or bridging capacitor 27, can also be provided in sensor 10. Similar structural components can also be provided for other sensors 30. Furthermore, the sensor system may include more than one other sensor 30.

[0043] Figure 5A flowchart 120 is shown for a method of operating sensor 10, which can be executed, for example, by a calculation unit 81 of an analysis processing unit 80. In a first method step 121, sensor 10 is excited at a predetermined frequency. In a second method step 122, a complex impedance is determined. In a third method step 123, two measurement parameters are calculated from the complex impedance. In the third method step 123, these two measurement parameters can be calculated, in particular, based on a model stored for sensor 10. The measurement parameters can then be output if necessary. The complex impedance can include magnitude and phase, wherein these two measurement parameters are calculated from the magnitude and phase of the complex impedance. Alternatively, analysis can be performed via the real and imaginary parts of the complex impedance.

[0044] Here, the excitation of sensor 10 in step 121 of the first method can be achieved by combining... Figure 3 The extreme frequency 106 is used for this purpose. It can be assumed, for example, that if the gas concentration at sensor 10 also changes only slowly, the extreme frequency 106 determined in previous measurements will change only slightly over time. In particular, the same timescale may be relevant for both types of changes. Therefore, the extreme frequency 106 can continue to be used in subsequent measurements. It can thus be assumed that subsequent impedance spectra over time will have a similar shape and extreme or maximum values ​​located in nearby phases. The assumption of a slowly changing extreme frequency can also be utilized by using previous extreme frequencies as a starting point for searching for new extreme frequencies, for example, within the framework of a frequency scan.

[0045] for Figure 5 The method, and for the analysis and processing unit 80, can be set as follows: First, the extreme frequency 106 can be determined. This can be done, for example, by exciting the sensor 10 with multiple pre-given frequencies via the connection terminal 82 and determining the extreme frequency 106 therefrom. Then, as in combination Figure 3 As explained, these two measurement parameters are determined by the magnitude 104 and phase 102 of the complex impedance at the extreme frequency 106, and by that extreme frequency 106.

[0046] To find the extreme frequency 106, various possibilities can be used. For example, a raster scan can be performed in a fixed-frequency scheme (e.g., in frequency steps), and a restricted raster scan can be accepted, with the extreme value of the raster scan considered sufficiently close to the true extreme frequency 106. Alternatively or additionally, an iterative method can be chosen, which may, for example, draw upon interval bisection or conventional methods in numerical optimization. In a combination, for example, a coarse raster scan can be used, followed by a finer raster scan first over a narrower range.

[0047] Figure 6Another embodiment of the sensor 10 is shown, wherein the second electronic equivalent circuit diagram 22 of the second sensing element 12 includes a second resistor 28. The second electronic equivalent circuit diagram 22 includes a parallel circuit consisting of the second resistor 28 and the second capacitor 25. Furthermore, the sensor 10 optionally has a third sensing element 13 with a third material 16, which is connected in series with the second sensing element 12 and the first sensing element 11. Therefore, via the control connection terminal 17, three sensing elements 11, 12, 13 (or even more sensing elements, but not shown here) can be controlled if necessary. The third sensing element 13 has a third resistor 54 and a third capacitor 55. The third electronic equivalent circuit diagram 53 of the third sensing element 13 has a parallel circuit consisting of the third resistor 54 and the third capacitor 55. Such a sensor 10 is more advanced than a combination of... Figure 1 and Figure 2 The described sensors are more general and can include, for example, gas sensors, humidity sensors, and pressure sensors. (Combined) Figure 5 The method described herein can also be used in this principle, and specifically includes: in the first method step 121, exciting the sensor 10 at a pre-given frequency; in the second method step 122, determining the complex impedance with magnitude and phase; and in the third method step 123, calculating two measurement parameters from the magnitude and phase of the complex impedance. The measurement parameters can also be output thereafter if necessary. It can be configured such that in the first method step 121, the sensor 10 is excited at multiple frequencies via the connection terminal 82, and more than two measurement parameters are determined based on the magnitude and phase of the complex impedance at these frequencies. This can also be done based on a model stored for the sensor 10. In particular, for… Figure 6 The sensor 10 shown can determine the measurement parameters independently of extreme frequencies. Similarly, for... Figure 6 The sensor 10 can also be similar to Figure 2 A bridging resistor 26 and / or a bridging capacitor 27 are provided for each sensing element 11, 12, 13. The third material 16 may be a third sensing material.

[0048] Therefore, in principle, two, three, or even more complete RC loops can be provided for the corresponding sensing elements 11, 12, and 13. Thus, reconstructing completely arbitrary resistors 23, 28, and 54 or capacitors 24, 25, and 55 will no longer be possible. However, the diversity of measured values ​​can be limited by the specific materials 14, 15, and 16 used and the geometry of the receiving layer used, and, if necessary, also by their operating temperatures. For example, for the first sensing element 11 and the second sensing element 12, the first resistor 23 can always be significantly smaller than the second resistor 28, where the second resistor 28 is almost constant. The second capacitor 25 can be variable, and the ratio of the first resistor 23 to the second capacitor 25 can be within a defined preset range, thereby re-establishing the asymmetry between the first electronic equivalent circuit diagram 21 and the second electronic equivalent circuit diagram 22. The third electronic equivalent circuit diagram 53 can also have further asymmetries.

[0049] Therefore, it is typically possible to record impedance spectra with a preset number j of measurements, and reconstruct k elements of individual resistive (23, 28, 54) and capacitive (24, 25, 55) elements from more than two sensing elements 11, 12, 13, from which conclusions about the concentrations of n gases and vapors can be drawn. Alternatively, the step of obtaining the tuples composed of capacitance and associated resistance can be skipped, and the n concentrations can be directly obtained from the preset number j of measurements using characteristic plots and models.

[0050] Another method for increasing the asymmetry of sensing elements 11, 12 is to operate the first sensing element 11 and the second sensing element 12 at different operating temperatures. For this purpose, a heating element (not shown in the figures) can be used to heat the first sensing element 11 or the second sensing element 12.

[0051] Although the invention has been described in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, and other variations can be derived by those skilled in the art without departing from the scope of protection of the invention.

Claims

1. A sensor (10) for determining two measurement parameters of a gas, comprising at least one first sensing element (11) and a second sensing element (12) and two control connection terminals (17), wherein, The first sensing element (11) and the second sensing element (12) are connected in series, wherein the sensing elements (11, 12) are arranged between the control connection terminals (17), wherein the first sensing element (11) has a first electronic equivalent circuit diagram (21), wherein the first electronic equivalent circuit diagram (21) includes a parallel circuit consisting of a first resistor (23) and a first capacitor (24), wherein the second sensing element (12) has a second electronic equivalent circuit diagram (22), wherein the second electronic equivalent circuit diagram (22) includes a second capacitor (25).

2. The sensor (10) according to claim 1, wherein, The first sensing element (11) and the second sensing element (12) are arranged on a common sensor chip (18).

3. The sensor (10) according to claim 1 or 2, wherein, The second electronic equivalent circuit diagram (22) of the second sensing element (12) includes a second resistor (28), and wherein the second electronic equivalent circuit diagram (22) includes a parallel circuit consisting of the second resistor (28) and the second capacitor (25).

4. The sensor (10) according to any one of claims 1 to 3, wherein, The first sensing element (11) has a bridging resistor (26), wherein the bridging resistor (26) is arranged in parallel with the parallel circuit consisting of the first resistor (23) and the first capacitor (24).

5. The sensor (10) according to any one of claims 1 to 4, wherein, The second sensing element (12) has a bridging capacitor (27), wherein the bridging capacitor (27) is arranged in parallel with the second capacitor (25).

6. An analysis and processing unit (80) having a computing unit (81) and at least two connection terminals (82), wherein, The connection terminal (82) can be connected to the control connection terminal (17) of the sensor (10) according to any one of claims 1 to 5, wherein the analysis and processing unit (80) is configured to: excite the sensor (10) via the connection terminal (82) at a pre-given frequency, determine the complex impedance, and calculate the two measurement parameters from the complex impedance.

7. The analysis and processing unit (80) according to claim 6, wherein, The analysis and processing unit (80) is configured to: excite the sensor (10) via the connection terminal (82) at a plurality of pre-given frequencies, determine an extreme frequency (106), and determine the two measurement parameters by the magnitude (104) and phase (102) of the complex impedance at the extreme frequency (106) and the extreme frequency.

8. The analysis and processing unit (80) according to claim 6 or 7, wherein, The analysis and processing unit (80) is configured to: excite the sensor (10) at multiple frequencies via the connection terminal (82) and determine more than two measurement parameters based on the magnitude and phase of the complex impedance at the multiple frequencies.

9. A sensor system (1) having a sensor (10) according to any one of claims 1 to 5 and an analysis and processing unit (80) according to any one of claims 6 to 8.

10. A method for operating a sensor (10) according to any one of claims 1 to 5, comprising the following steps: The sensor (10) is excited at a predetermined frequency. Determine the complex impedance; and Two measurement parameters are calculated from the complex impedance.

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