Sensor arrangement for a swirl meter and method for a swirl meter

Abstract

The invention relates to a sensor arrangement for a swirl meter for detecting swirls in a medium (ME), comprising: two measuring capacitors (MK1, MK2) each having a measurement capacitance (C1, C2), wherein at least one of the measuring capacitors (MK1, MK2) has a measuring electrode (EL) that can be deflected depending on the swirls, such that said one measuring capacitor (MK1, MK2) has a variable measurement capacitance (C1, C2); a measuring and operating circuit (MB), wherein the measuring and operating circuit (MB) has a compensation capacitor arrangement (KA) having compensation capacitors (KK); wherein the measuring and operating circuit (MB) is designed to detect measurement signals (MS1, MS2) which are respectively dependent on the measurement capacitances (C1, C2), to form the difference (D) between said measurement signals, and to detect the swirls on the basis of the time profile of the difference (D); wherein the measuring and operating circuit (MB) is designed to interconnect at least one of the compensation capacitors (KK) having a compensation capacitance (C') with one of the measuring capacitors (MK1, MK2) in order to carry out a compensation of the measurement capacitance (C1, C2) of said measuring capacitor (MK1, MK2) with respect to a deviation (A).

Description

[0001] Sensor arrangement for a vortex counter and method for a vortex counter

[0002] The invention relates to a sensor arrangement for a vortex counter with an offset compensation integrated in the sensor electronics, and to methods for counting vortices of a Kärmännian vortex street in a medium by means of a vortex counter with a sensor arrangement according to the invention.

[0003] Vortex flow sensors are used to precisely measure the flow velocity or volumetric flow rate of a fluid flowing in a specific direction. German patent DE102013105363A1 describes such a sensor with a measuring tube, the measuring tube having a baffle element positioned upstream of a vortex sensor. The baffle element generates a Kärmännian vortex street in the fluid, the pressure fluctuations of which are converted into an electrical signal by a downstream vortex sensor, with the frequency of the measured vortices being proportional to the volumetric flow rate.

[0004] Vortex flow sensors, or simply vortex sensors, for such measuring devices are known from the prior art, including from EP0841545B1. This document describes a capacitive vortex sensor that is used in a measuring tube to measure flow velocity or volumetric flow rate. Essentially, the vortex sensor comprises a housing containing a diaphragm. A movable electrode, referred to as a sensor paddle, is attached to the side of the diaphragm facing the fluid flowing in the measuring tube. A capacitive electrode array is arranged on the side of the diaphragm facing away from the fluid. One electrode is connected to the diaphragm itself. The sensor paddle is set into oscillation and deflected by the vortices of the Kärmännian vortex street. This deflection is transmitted proportionally to the electrode array, resulting in a change in capacitance.

[0005] A sensor array in a vortex flow meter detects the capacitance change of the sensor paddle as a capacitance signal, which can be fractions of fF. After charge amplification, the signal is given by a function of the sinusoidal capacitance change and oscillates between a maximum and a minimum value, with a frequency dependent on the flow rate of the medium.

[0006] Ideally, the capacitance signal consists of only one useful component and is therefore symmetrically arranged around a zero point. In practice, however, the capacitance signal usually exhibits a noise component, which results in a deviation of the sinusoidal signal from the zero point. Often, a deviation caused by a noise component has a magnitude comparable to, or even greater than, the amplitude of the useful component. The problem with vortex counters with movable center electrodes is that a deviation caused by a noise component limits the processing of the useful component, thus impairing the accuracy of the measurement.

[0007] The task to be solved is therefore the compensation of the interference component of a capacitance signal.

[0008] The invention solves the problem through the subject matter of claim 1.

[0009] The sensor arrangement according to the invention for a vortex counter for detecting vortices in a medium flowing through a measuring tube comprises: two measuring capacitors, each with a measuring capacitance, wherein at least one of the measuring capacitors has a measuring electrode that can be deflected depending on the vortices, so that this at least one measuring capacitor has a variable measuring capacitance; a measuring and operating circuit, wherein the measuring and operating circuit has a compensation capacitor arrangement with compensation capacitors; wherein the measuring and operating circuit is configured to detect measuring signals that depend on the measuring capacitances, to calculate their difference, and to detect the vortices based on the time course of the difference;wherein the measuring and operating circuit is configured to connect at least one of the compensation capacitors with a compensation capacitance to at least one of the measuring capacitors in order to compensate the measuring capacitance of this at least one measuring capacitor with respect to a deviation.

[0010] In a further development of the sensor arrangement according to the invention, the deflectable measuring electrode comprises a common central electrode of both measuring capacitors, wherein the measuring capacitors each further comprise a rigid electrode; wherein a deflection of the central electrode changes the measuring capacitance of the two measuring capacitors in opposite directions.

[0011] In a further development of the sensor arrangement according to the invention, the compensation serves to ensure that the difference of the measurement signals lies within a working range, in particular an amplifier arrangement, of the measurement and operating circuit.

[0012] In a further development of the sensor arrangement according to the invention, the operating range, particularly for an amplifier arrangement, of the measuring and operating circuit lies below 20 pF, particularly below 40 pF, preferably below 60 pF, for a difference in the measuring signals. In a further development of the sensor arrangement according to the invention, the measuring signal is a voltage or a current.

[0013] In a further development of the sensor arrangement according to the invention, the measuring and operating circuit, in particular by means of an amplifier arrangement, is configured to generate an amplified signal based on the difference by amplifying the difference of the measuring signals with at least 0.125 V / pF, and at most 128 V / pF, in particular at most 64 V / pF, and preferably at most 32 V / pF.

[0014] In a further development of the sensor arrangement according to the invention, the measuring and operating circuit is configured to acquire the measurement signals and calculate their difference with a first clock frequency of at least 64 kHz, in particular at least 160 kHz and preferably at least 480 kHz.

[0015] In a further development of the sensor arrangement according to the invention, the compensation capacitors from the compensation capacitor arrangement have capacitances; wherein at least one capacitance has between 1 fF and 6 fF; wherein a sum of the capacitances has at least 6 pF, in particular 12 pF, preferably 24 pF.

[0016] In a further development of the sensor arrangement according to the invention, the compensation capacitor arrangement has no fewer than 8 compensation capacitors.

[0017] In a further development of the sensor arrangement according to the invention, the difference of the measurement signals has a useful component and a disturbance component; wherein the measuring and operating circuit is configured to detect the vortices by means of a time-varying frequency of the useful component that depends on the vortices; wherein the measuring and operating circuit is configured to detect the deviation by means of an average value of the disturbance component, which is constant in time or changes slowly in comparison with the frequency of the useful component.

[0018] In a further development of the sensor arrangement according to the invention, the measuring and operating circuit is configured to determine the interference component with a second clock of at least 10 Hz, in particular at least 100 Hz, preferably at least 1 kHz.

[0019] In a further development of the sensor arrangement according to the invention, the measuring and operating circuit comprises a first switching module and a second switching module; wherein the first switching module comprises the compensation capacitor arrangement; wherein the first switching module is configured to receive and process the measurement signals, in particular to amplify them by means of an amplifier arrangement, and to transmit them to the second switching module; wherein the second switching module is configured to further process the amplified measurement signals and to transmit them to a higher-level unit.

[0020] In a further development of the sensor arrangement according to the invention, the first switching module and the second switching module are structurally separated, in particular arranged on separate printed circuit boards; wherein the first switching module is configured to execute an algorithm; wherein the algorithm is configured to instruct the measuring and operating circuit which of the compensation capacitors are to be connected to the at least one measuring capacitor in order to compensate the measuring capacitance of this measuring capacitor with respect to the deviation.

[0021] In a further development of the sensor arrangement according to the invention, the first switching module, in particular the compensation capacitor arrangement, comprises a differentially switched capacitor.

[0022] The inventive method for counting vortices of a Kärmännschen vortex street in a medium by means of a vortex counter which has a sensor arrangement, in particular according to one of the preceding claims, wherein the sensor arrangement has measuring capacitors and a measuring and operating circuit, wherein the measuring capacitors have at least one variable measuring capacitance dependent on vortices, wherein the measuring and operating circuit has a compensation capacitor arrangement with compensation capacitors, at least comprising the following steps: Acquiring the measurement signals by means of the measuring and operating circuit with a first clock of at least 10 kHz, in particular at least 50 kHz, preferably 100 kHz;Forming a difference between the measurement signals of the measuring capacitors using the measuring and operating circuit, wherein the difference of the measurement signals has a useful component and a noise component, the useful component changing over time at a frequency dependent on the vortices, and the noise component, which depends on a deviation, being constant over time or changing slowly compared to the frequency of the useful component; determining a deviation of the noise component by forming an average value of the difference using the measuring and operating circuit, in particular with a second clock of at least 100 Hz, preferably 1 kHz; connecting at least one compensation capacitor (KK) from the compensation capacitor arrangement (KA) with at least one of the measuring capacitors (MK1; MK2) using the measuring and operating circuit (MB), wherein the connection serves to ensure that the magnitude of the deviation (A) is below a setpoint value;Evaluating the frequency (F) of the useful component (N), especially when amplified with an amplifier chain, for counting vortices.

[0023] The invention has the advantage that the compensation capacitor arrangement and the ASIC chip (Application Specific Integrated Circuit) are part of the first switching module, in particular the sensor electronics, so that measurement signals with clock rates of over 64 kHz can be evaluated to compensate for the deviation.

[0024] Furthermore, there is the advantage that structurally caused deviations in the capacitance signal, for example because the measuring capacitances of the two measuring capacitors at the center electrode or sensor paddle in the rest position are not exactly identical, can be compensated for up to a difference of 12 pF.

[0025] Furthermore, the compensated signal is amplified by means of a preamplifier with an automatically and at high frequency adjusting gain of up to 64 V / pF, so that the vortices can be detected on the basis of the amplified signal.

[0026] Furthermore, there is the advantage that the second switching module can be arranged on a printed circuit board, whereby the compensation capacitor arrangement can be implemented as a differentially switched capacitor.

[0027] The invention is explained in more detail with reference to the exemplary embodiments shown in the following figures. These show:

[0028] Fig. 1 shows a cross-section of an embodiment of the sensor arrangement according to the invention.

[0029] Fig. 2 shows an embodiment of the measuring capacities of the sensor arrangement according to the invention.

[0030] Fig. 3 shows a circuit diagram of an embodiment of the measuring and operating circuit according to the invention.

[0031] Fig. 4 shows a circuit diagram of an embodiment of the compensation capacitor arrangement according to the invention.

[0032] Fig. 5 shows an embodiment of the difference of the measurement signals according to the invention.

[0033] Fig. 6 shows an embodiment of the compensated and amplified signal according to the invention.

[0034] Fig. 7 shows an embodiment of the inventive method for counting vortices.

[0035] The cross-section shown in Fig. 1 of an embodiment of the sensor arrangement according to the invention shows the movable electrode EL, also referred to as a sensor paddle, projecting into the measuring tube MR. This electrode changes the capacitances C1 and C2 of the measuring capacitors MK1 and MK2 depending on the eddies occurring in the medium ME. The measuring capacitors MK1 and MK2 are connected to the first switching module MB1 of the measuring and operating circuit MB. The first switching module MB1 comprises the compensation capacitor arrangement KA and is connected to the second switching module MB2 of the measuring and operating circuit MB.In this embodiment, the first switching module MB1 comprises a printed circuit board containing the sensor electronics, the compensation capacitor arrangement KA, and an ASIC (Application Specific Integrated Circuit) chip. This ASIC chip includes an algorithm configured to instruct the first switching module which of the compensation capacitors KK are to be connected to the at least one measuring capacitor MK1, MK2 in order to compensate the measuring capacitance C of this measuring capacitor MK1, MK2 with respect to the deviation A. The second switching module MB2, in this embodiment, comprises the main electronics of a measuring device and may include further electronic assemblies.

[0036] The embodiment of the measuring capacitances of the sensor arrangement according to the invention, shown in Fig. 2, depicts the two measuring capacitors MK1, MK2, which, together with their respective rigid electrodes SE1, SE2 and the common movable central electrode MEL, each form a measuring capacitance C1, C2. The deflection of the common central electrode, which depends on the eddies occurring in the medium ME and changes over time, alters the two measuring capacitances C1, C2 in opposite directions.

[0037] The circuit diagram shown in Fig. 3 of an embodiment of the measuring and operating circuit MB according to the invention shows the two measuring capacitors MK1, MK2, which together with the reference potentials REF1, REF2 are connected to the first switching module MB1 of the measuring and operating circuit MB. The first switching module MB1 is connected to the second switching module MB2, which in turn is connected to a higher-level unit HE, wherein the higher-level unit HE can, for example, comprise a control unit, a data processing unit, or a computer system.

[0038] The first switching module MB1 comprises the compensation compensator arrangement, which in this configuration has 12 compensation capacitors with a total capacitance of 13.65 pF. This allows for compensation of a difference D between the measurement signals MS1 and MS2 of the measurement capacitors MK1 and MK2 from -12 pF to +12 pF. Each compensation capacitor KK has a minimum capacitance of 3.33 fF, giving the compensation capacitor arrangement KA a capacitance resolution of 3.33 fF. The first switching module MB1 connects a selection of compensation capacitors KK from the compensation compensator arrangement KA with at least one of the measurement compensators MK1 and MK2, and calculates the difference D between the measurement signals MS1 and MS2 at a first clock rate of over 100 kHz.The first switching module MB1 comprises an ASIC (Application Specific Integrated Circuit) that executes an algorithm which determines the deviation A by integrating a disturbance component S of the difference D over several, in particular at least 10, preferably at least 100, periods of a frequency F of a useful component N of the difference D. Based on the determined deviation A, the algorithm selects compensation capacitors KK with a compensation capacitance C' from the compensation capacitor arrangement KA, such that a compensated signal is generated from the sum of the difference D and the compensation capacitance C'.

[0039] The first switching module MB1 features an amplifier arrangement to amplify the compensated signal. The amplifier arrangement includes a first charge amplifier with a variable capacitance Cfch to convert a charge associated with the compensated signal into a voltage signal with a voltage between -0.9 V and +0.9 V.

[0040] The amplifier arrangement further includes another capacitor Cisc, through which a portion of the useful component N of the voltage signal generated by the charge amplifier is passed to a second charge amplifier with adjustable capacitance Csch, thereby creating an amplified signal VS that depends on the useful component N, which is amplified by the amplifier arrangement as a whole with up to 64 V / pF.

[0041] The amplified signal VS is transmitted to the second switching module MB2, where it is further processed and, if necessary, transmitted to the higher-level unit HE.

[0042] The circuit diagram shown in Fig. 4 of an embodiment of the compensation capacitor arrangement KA according to the invention shows, in a first area, several compensation capacitors KK, which are arranged in a capacitor network. The polarity of the arrangement is controlled by means of charging switches VREFP, VREFN, VREF2, VGNDA, wherein the charging switches VREFP and VREFN are configured to charge the compensation capacitor arrangement with a positive or negative charge, respectively.

[0043] The circuit diagram shows, in a second section, a number of dummy switches configured to compensate for the capacitance of the charging switches VREFP, VREFN, VREF2, and VGNDA of the compensation capacitor array in the first section. These dummy switches are connected in parallel to the components of the upper section and also feature charging switches VREFP, VREFN, VREF2, and VGNDA, which are configured to charge the parasitic capacitors CP and the capacitances of the dummy switches with reverse polarity. The circuit can be implemented on a suitable ASIC (Application Specific Integrated Circuit) and is designed such that a suitable ASIC can autonomously implement any desired circuit. For example, based on a deviation A of the mean value of a difference D between measurement signals MS1 and MS2, a suitable circuit can be implemented to compensate for the deviation A.

[0044] The embodiment of the difference D of the measurement signals MS1, MS2 shown in Fig. 5 depicts the course of this difference D as a function of time t, comprising a disturbance component S – which is constant in the temporal course shown here – and a useful component N oscillating with a frequency F and having an amplitude, which useful component, in particular the frequency F, depends on eddies occurring in the medium ME. Determining the frequency F of the useful component N enables the determination of properties of the medium ME, in particular the determination of the flow velocity of the medium ME.

[0045] The amplitude of the useful component is often between 0.06 pF and 6 pF, but can also be as low as 0.03 pF, for example. The deviation A can be several pF; often, due to production factors, it is between 0.2 pF and 3 pF, but it can be significantly larger, so that amplifying the useful component N requires compensating for the deviation A and subsequently increasing the charge.

[0046] In this embodiment, the compensation of the deviation A is carried out by the first circuit arrangement MB1 of the measuring and operating circuit MB by connecting compensation capacitors KK with a capacitance C', wherein the capacitance C' is selected such that it determines the deviation A based on the disturbance component S. In this embodiment, the deviation A is determined, for example, by means of an average value MW of the difference D averaged over several, in particular at least 10, preferably at least 100, periods given by the frequency F of the useful component.

[0047] The embodiment of the compensated and amplified signal VS as a function of time t shown in Fig. 6 exhibits a sinusoidal voltage waveform with an amplitude and an offset, wherein the magnitudes of the amplified signal VS are smaller than the saturation voltage of an amplifier arrangement, in this specific case 1 V, and wherein the amplitude of the amplified signal VS is significantly larger than the vertical offset to the horizontal time axis. A frequency of the amplified signal VF is identical to the frequency F of the useful component N of the difference between the measurement signals MS1 and MS2 and enables the determination of properties of the medium ME, in particular a flow velocity.

[0048] The embodiment of the method according to the invention for counting vortices, shown in Fig. 7, depicts the measurement signals MS1, MS2 transmitted by the measuring capacitors MK1, MK2 with the measuring capacitances C1, C2 to the measuring and operating circuit MB. The first switching module MB1 of the measuring and operating circuit MB forms the difference D of the same measurement signals MS1, MS2, which has a useful component N and a noise component S.

[0049] The difference D and the useful signal N are essentially sinusoidal, whereby the interference signal in this embodiment is essentially constant over time, or changes relatively slowly compared to the temporal evolution of the useful signal.

[0050] Based on the interference component S, the deviation A of the difference D is determined. This deviation A is used by the first switching module MB1 to select a range of compensation capacitors KK with capacitance C' from the compensation capacitor arrangement KA, and to connect this selection of compensation capacitors KK with at least one measuring capacitor MK1, MK2 (in this specific case, MK2) to compensate for the deviation A. As a result of connecting the selection of compensation capacitors KK with capacitance C', the deviation A of the interference component S is minimized, and the useful component N is amplified by the measuring and operating circuit MB, in particular by an amplifier arrangement, so that the frequency F of the useful component can be evaluated to count the eddies in the medium ME.

[0051] Reference symbol list

[0052] MR measuring tube

[0053] ME Medium

[0054] MK1 and MK2 measuring capacitors

[0055] C1, C2 measuring capacity

[0056] EL measuring electrode

[0057] MB measuring and operating circuit

[0058] KA compensation capacitor arrangement

[0059] KK compensation capacitors

[0060] MS1. MS2 Measurement signals

[0061] D difference

[0062] C' compensation capacity

[0063] CFCH adjustable capacity

[0064] Cisc another capacitor

[0065] Csch charge amplifier with adjustable capacitance

[0066] VREFP, VREFN, VREF2, VGNDA charging switch

[0067] CP Parasitic Capacitor

[0068] A deviation

[0069] MEL center electrode

[0070] SE1, SE2 Rigid electrode

[0071] REF1, REF2 Reference Potential

[0072] VS Amplified signal t time

[0073] F Frequency

[0074] N Utility component

[0075] S interference component

[0076] Mean value MB1. MB2 switching modules

[0077] HE Higher-level unit

Claims

Patent claims 1. Sensor arrangement for a vortex counter for detecting vortices in a medium (ME) flowing through a measuring tube (MR), comprising: • Two measuring capacitors (MK1, MK2) each with a measuring capacitance (C1, C2), wherein at least one of the measuring capacitors (MK1, MK2) has a measuring electrode (EL) that can be deflected depending on the vortices, so that at least one measuring capacitor (MK1, MK2) has a variable measuring capacitance (C1, C2); • a measuring and operating circuit (MB), wherein the measuring and operating circuit (MB) comprises a compensation capacitor arrangement (KA) with compensation capacitors (KK); • wherein the measuring and operating circuit (MB) is set up to detect measuring signals (MS1 , MS2) that depend on the measuring capacitances (C1 , C2), to form their difference (D) and to detect the vortices based on the time course of the difference (D); • wherein the measuring and operating circuit (MB) is configured to connect at least one of the compensation capacitors (KK) with a compensation capacitance (C') to at least one of the measuring capacitors (MK1, MK2) in order to perform a compensation of the measuring capacitance (C1 , C2) of this at least one measuring capacitor (MK1 , MK2) with respect to a deviation (A).

2. Sensor arrangement according to claim 1 , • wherein the deflectable measuring electrode (EL) comprises a common center electrode (MEL) of both measuring capacitors (MK1 , MK2), wherein the measuring capacitors (MK1, MK2) furthermore each comprise a rigid electrode (SE1 , SE2); • where a deflection of the center electrode (MEL) changes the measuring capacitance (C1, C2) of the two measuring capacitors (MK1 , MK2) in the opposite direction.

3. Sensor arrangement according to one of claims 1 or 2, • wherein the compensation serves to ensure that the difference (D) of the measurement signals (MS1, MS2) lies within a working range, in particular an amplifier arrangement, of the measurement and operating circuit (MB).

4. Sensor arrangement according to claim 3, • wherein the operating range, in particular for an amplifier arrangement, of the measuring and operating circuit (MB) is below 20 pF, in particular below 40 pF, preferably below 60 pF for an amount of the difference (D) of the measuring signals (MS1, MS2).

5. Sensor arrangement according to one of claims 1 to 4, • where the measurement signal (MS1; MS2) is a voltage or a current.

6. Sensor arrangement according to one of claims 1 to 5, • wherein the measuring and operating circuit (MB), in particular by means of an amplifier arrangement, is configured to generate an amplified signal (VS) based on the difference (D) by amplifying the difference (D) of the measuring signals (MS1, MS2) with at least 0.125 V / pF, and at most 128 V / pF, in particular at most 64 V / pF, and preferably at most 32 V / pF.

7. Sensor arrangement according to one of claims 1 to 6, • wherein the measuring and operating circuit (MB) is configured to acquire the measuring signals (MS1 , MS2) and to calculate their difference with a first clock of at least 64 kHz, in particular at least 160 kHz and preferably at least 480 kHz.

8. Sensor arrangement according to one of claims 1 to 7, • wherein the compensation capacitors (KK) from the compensation capacitor arrangement (KA) have capacitances; • wherein at least one has a capacity between 1 fF and 6 fF; • wherein the sum of the capacitances is at least 6 pF, in particular 12 pF, preferably 24 pF.

9. Sensor arrangement according to one of claims 1 to 8, • wherein the compensation capacitor arrangement (CA) has no fewer than 8 compensation capacitors (CC).

10. Sensor arrangement according to one of claims 1 to 9, • wherein the difference (D) of the measurement signals (MS1, MS2) has a useful component (N) and a noise component (S); • wherein the measuring and operating circuit (MB) is configured to detect the vortices by means of a time-varying frequency of the useful component (N) that depends on the vortices; • wherein the measuring and operating circuit (MB) is set up to detect the deviation (A) by means of a mean value (MW) of the time constant or slowly changing disturbance component (S) compared with the frequency of the useful component (N).

11. Sensor arrangement according to claim 10, • wherein the measuring and operating circuit (MB) is configured to determine the interference component (S) with a second clock of at least 10 Hz, in particular at least 100 Hz, preferably at least 1 kHz.

12. Sensor arrangement according to one of claims 1 to 11, • wherein the measuring and operating circuit (MB) comprises a first switching module (MB1) and a second switching module (MB2); • wherein the first switching module (MB1) comprises the compensation capacitor arrangement (KA); • wherein the first switching module (MB1) is configured to receive and process the measurement signals (MS1, MS2), in particular to amplify them by means of an amplifier arrangement, and to transmit them to the second switching module (MB2); • wherein the second switching module (MB2) is configured to further process the amplified measurement signals (MS1, MS2) and transmit them to a higher-level unit (HE).

13. Sensor arrangement according to claim 12, • wherein the first switching module (MB1) and the second switching module (MB2) are structurally separate, in particular arranged on separate circuit boards; • wherein the first switching module (MB1) is configured to execute an algorithm; • wherein the algorithm is set up to instruct the measuring and operating circuit (MB) which or which of the compensation capacitors (KK) are to be connected to the at least one measuring capacitor (MK1 , MK2) in order to compensate the measuring capacitance (C) of this measuring capacitor (MK1, MK2) with respect to the deviation (A).

14. Sensor arrangement according to one of claims 12 or 13, • wherein the first switching module (MB1), in particular the compensating capacitor arrangement (KA), comprises a differential switched capacitor.

15. Method for counting vortices of a Kärmänschen vortex street in a medium (ME) by means of a vortex counter which has a sensor arrangement, in particular according to one of the preceding claims, wherein the sensor arrangement has measuring capacitors (MK1, MK2) and a measuring and operating circuit (MB), wherein the measuring capacitors (MK1, MK2) have at least one vortex-dependent variable measuring capacitance (C), wherein the measuring and operating circuit (MB) has a compensation capacitor arrangement (KA) with compensation capacitors (KK), at least comprising the following steps: • Acquisition of measurement signals (MS1, MS2) by means of the measurement and operating circuit (MB) with a first clock of at least 10 kHz, in particular at least 50 kHz, preferably 100 kHz; • Forming a difference (D) of the measurement signals (MS1, MS2) of the measuring capacitors (MK1, MK2) using the measurement and operating circuit (MB), wherein the difference (D) of the measurement signals (MS1, MS2) has a useful component (N) and a disturbance component (S), wherein the useful component (N) changes over time with a frequency (F) dependent on the vortices, wherein the disturbance component (S) dependent on a deviation (A) is constant over time or changes slowly compared with the frequency (F) of the useful component (N); • Determining a deviation (A) of the disturbance component (S) by forming an average value (MW) of the difference (D) using the measuring and operating circuit (MB), in particular with a second clock of at least 100 Hz, preferably 1 kHz; • Interconnecting at least one compensation capacitor (KK) from the compensation capacitor arrangement (KA) with at least one of the measuring capacitors (MK1 , MK2) by means of the measuring and operating circuit (MB), wherein the interconnection serves to ensure that an amount of the deviation (A) is below a setpoint value; • Evaluating the frequency (F) of the useful component (N), especially when amplified with an amplifier chain, for counting vortices.

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