Electronic vibration sensor

Abstract

The invention relates to an electronic vibration sensor (1) and a method for operating the sensor (1), wherein the sensor (1) is used for determining and / or monitoring at least one process variable of a medium (2) in a container (3), and the sensor (2) comprises at least one mechanically vibrable unit (4), a drive / receiver unit (5) and an electronics unit (6). The drive / receiver unit (5) is designed to: A ) excites the mechanical vibration in the mechanically vibrating unit (4), and receives the mechanical vibration of the mechanically vibrating unit (4) and converts it into an electrical receiving signal (U E The electronic unit (6) is designed to: based on the received signal (U E ) generates the excitation signal (U A ), and according to the received signal (U E ) determines the at least one process variable. The electronic unit (6) further comprises a first adaptive filter (7) and is designed to set the filter characteristics of the adapter filter (7) so that in the case of an excitation signal (U A ) and the received signal (U E ) produces a target phase shift (ΔΦ soll The sensor (1) also has a detection unit (10) designed to determine the excitation signal (U A ) and the phase shift (ΔΦ) between the received signal and / or the received signal (U E )’s amplitude (A).

Description

Technical Field

[0001] The invention relates to a vibratory electronic sensor for determining and / or monitoring at least one process variable of a medium and to a method for operating the vibratory electronic sensor. Background Art

[0002] Vibratory electronic sensors are often used in process and / or automation engineering. In the case of level measuring devices, they have at least one mechanically vibratory unit, such as a vibrating fork, a rod, or a diaphragm. During operation, a drive / receiver unit, typically in the form of an electromechanical transducer unit, which in turn can be, for example, a piezoelectric drive or an electromagnetic drive, excites mechanical vibrations in the mechanically vibratory unit. However, in the case of flow meters, such as measuring devices operating according to the Coriolis principle, the mechanically vibratory unit can also be designed as a vibratory tube through which the corresponding medium flows.

[0003] The applicant manufactures a wide variety of corresponding field devices, which, in the case of fill level measuring devices, are marketed under names such as LIQUIPHANT or SOLIPHANT. The basic measuring principle is generally known from numerous publications. A driver / receiver unit excites a mechanically vibrating unit with an electrical excitation signal, thereby inducing mechanical vibrations. Conversely, the driver / receiver unit can receive the mechanical vibrations of the mechanically vibrating unit and convert them into electrical receive signals. The driver / receiver unit can thus be either a separate driver unit and a separate receiver unit, or a combined driver / receiver unit.

[0004] Both the excitation signal and the received signal are characterized by their frequency, amplitude and / or phase. Therefore, the changes in these variables are usually used to determine the corresponding process variables, such as the predetermined material level of the medium in the container or the density and / or viscosity of the medium, or the medium flow through the pipe. For example, in the case of an electronic vibration level switch for liquids, a distinction is made between whether the vibrating unit is covered by the liquid or is vibrating freely. Therefore, the two states of free state and covered state are distinguished, for example, based on different resonant frequencies (i.e., frequency shifts). If the vibrating unit is covered by the medium, the density and / or viscosity can only be determined using such a measuring device.

[0005] The drive / receiver unit is usually part of a feedback electrical oscillating circuit, with the aid of which mechanical vibrations are excited in the mechanically vibrating unit. For the excitation, a predeterminable phase offset value, i.e., a target value for the phase offset between the excitation signal and the received signal, is usually set by a control circuit. For example, the resonant oscillation must satisfy an amplification factor ≥ 1 and oscillation circuit conditions according to which all phases occurring in the oscillation circuit result in multiples of 360°. Various methods for exciting mechanically vibrating units or for setting predeterminable phase offsets are known from the prior art. A basic distinction can be made here between analog excitation and digital excitation, where the distinction lies between the oscillation circuit, which consists of analog components that must be adapted to the type of sensor used, and digital methods, which are generally applicable.

[0006] According to the frequently used excitation principle, the control circuit includes an amplifier and a phase shifter, by means of which the received signal is fed back to the transmitted signal in order to set a predeterminable phase shift value between the excitation signal and the received signal. For example, DE 10 2006 034 105 A1 uses an adjustable phase shifter. The phase shifter is controlled by a control unit that measures the frequency of the previously amplified received signal and, based at least on stored data, by the frequency-phase dependence of the amplifier unit.

[0007] Also known from DE 10 2007 013 557 A1 is an amplifier having an adjustable amplification factor, which is set by a control unit such that the amplitude of the transmit signal lies essentially within a prescribable amplitude band.

[0008] DE 10 2005 015 547 A1 discloses an electronic vibration sensor in which the electronics unit is equipped with at least one all-pass filter for setting a target value for the phase shift. The all-pass filter changes the phase of the electrical signal with a constant gain as a function of frequency. In particular, the all-pass filter can be controlled or adjusted in such a way that the phase between the excitation signal and the received signal is adjustable. According to one embodiment of the invention, preferably only the received signal is filtered and / or amplified before it is supplied to the all-pass filter, processed by the all-pass filter, and returned.

[0009] However, with analog excitation, the analog components used to build the oscillating circuit must be adapted to the type of sensor used. Furthermore, the robustness of the sensor, particularly with respect to external vibrations, depends on the selectivity of the filters used in each case for signal processing and / or evaluation. The filters used determine the pitch of the phase response of the electronics unit. The larger the pitch of the phase response, the narrower the frequency range covered by the filter. Consequently, there may be situations where the sensor no longer vibrates resonantly.

[0010] DE 10 2009 026 685 A1 already discloses an excitation method in which mechanical vibrations in a mechanically oscillatable unit are excited successively at discrete excitation frequencies within a predeterminable frequency band within the unit's operating range, using so-called frequency sweeping within the unit's operating range, and corresponding received signals are received. The frequency sweep determines the excitation frequency at which the oscillatable unit vibrates at a vibration frequency corresponding to a predeterminable phase offset value. This excitation frequency is applied to the oscillatable unit in each case. An advantageous development of this method is the subject of DE 10 2009 028 022 A1, in which the evaluation of the received signal is simplified by selectively sampling and evaluating its phase only at specific moments. Similarly, DE102010030982A1 proposes sampling the received signal at predetermined discrete instants relative to the transmitted signal, comparing the sampled voltage values ​​of the received signal with the target value that the received signal has at that instant in the presence of a specifiable phase offset value, and, if the voltage value deviates from the target value, reducing or increasing the frequency of the transmitted signal based on whether the deviation is positive or negative.

[0011] However, in the case of excitation by frequency sweeping and evaluation of the individual phases and / or amplitudes of the received signal, it must be noted that there is a dependency between the sweep speed of the frequency sweep and the frequency resolution.

[0012] DE 0010 2010 030 982 A1 discloses an additional digital method for adjusting the phase offset between the excitation signal and the received signal in an electronic vibration sensor to a predeterminable value. This method is based on the functional principle of a phase-locked loop (PLL). Here, the frequency of the excitation signal is set so that a predeterminable phase offset exists between the excitation signal and the received signal.

[0013] Compared to excitation via frequency sweeps, this type of excitation offers significant advantages in terms of evaluation speed. However, it does require at least one phase detector, which can affect the robustness of the control, and therefore the stability, as well as the precision of the control circuit in the event of external vibrations. For stable evaluation, it is also necessary to ensure that the amplitude of the excitation signal remains constant.

[0014] In order to reduce problems caused by the occurrence of external vibrations (such as vibrations from a pump or an ultrasonic bath) during the operation of an electronic vibration sensor, DE102012101667A1 proposes to configure the control / evaluation unit in such a way that, in the presence of at least one external vibration, the vibration excitation is controlled depending on the frequency and / or amplitude of the external vibration so that the received signal is essentially not disturbed by the external vibration, and / or at least one frequency of the external vibration is suppressed.

[0015] In order to be able to operate independently of interference influences, an electronic vibration sensor is disclosed in the as-yet-unpublished German patent application with the reference number DE102014119061A1, whose electronics unit includes an adaptive filter. During ongoing operation of the electronic vibration sensor, the filter characteristics are set so as to produce a target phase offset between the excitation signal and the received signal. DE102016111134A1 further proposes an electronic vibration sensor whose electronics unit includes at least one adaptive filter. Two different operating modes are alternately performed, wherein in a first mode, mechanical vibrations are excited in the mechanically vibrating unit, and in a second operating mode, the vibrations are interrupted, and at least one value of the filter characteristic of the adaptive filter is set so as to produce a predeterminable phase offset between the excitation signal and the received signal. The entire contents of both applications are hereby referenced. Summary of the Invention

[0016] Starting from the aforementioned prior art, the present invention is based on the object of providing a vibronic sensor and a method for operating the sensor which are characterized by a high degree of measurement accuracy and a high degree of reliability.

[0017] This object is achieved by a vibronic sensor according to claim 1 and by a method for operating a vibronic sensor according to claim 11 .

[0018] The object underlying the present invention is achieved by an electronic vibration sensor for determining and / or monitoring at least one process variable of a medium in a container, the electronic vibration sensor comprising at least a mechanically vibratory unit, a drive / receiver unit, and an electronics unit, wherein the drive / receiver unit is designed to excite mechanical vibrations in the mechanically vibratory unit by means of an electrical excitation signal, and to receive the mechanical vibrations of the mechanically vibratory unit and convert them into an electrical receive signal, wherein the electronics unit is designed to generate the excitation signal based on the receive signal and to determine the at least one process variable based on the receive signal, and wherein the electronics unit includes a first adaptive filter and is designed to set the filter characteristics of the adaptive filter so as to produce a desired phase shift between the excitation signal and the receive signal. According to the invention, the sensor further comprises a detection unit designed to determine the phase shift between the excitation signal and the receive signal and / or the amplitude of the receive signal using quadrature demodulation.

[0019] The filter characteristics of a filter generally describe the behavior of the filter, i.e., the filter properties of the filter, and are determined by so-called filter requirements (such as filter requirements for the passband and filter requirements for the stopband). In some cases, the filter requirements also include specifications on group delay, maximum overshoot, edge steepness, center frequency, quality, etc. For example, one of the known filter characteristics, such as Bessel, Legendre, Butterworth, Chebyshev, Gaussian, etc., can be used. Depending on the selected filter characteristics, a transfer function is appropriately designed for the filter, by which the amplitude response, phase response, and frequency response are fully determined.

[0020] The filter characteristics of the adaptive filter can be set during operation. For example, the filter quality related to the bandwidth and the position of the center frequency can be set. Therefore, the phase offset Φ between the input signal and the output signal of the filter can be appropriately set by setting appropriate filter characteristics. Filter As a result of setting the phase shift between the input signal and the output signal of the filter to a specifiable value, the frequency of the excitation signal is set so as to produce Φ between the excitation signal and the received signal. soll =360°-Φ Filter The filter is adaptive, i.e., a filter that can be adjusted, so the filter quality can be improved without limiting the corresponding frequency range, as is the case with fixed filters. Setting the predeterminable phase offset via the filter is advantageously largely independent of disturbing influences such as external vibrations, making the electronic vibration sensor according to the invention particularly robust.

[0021] Adaptive filters enable field devices to be used in a wide range of applications. For example, the field device can operate with varying phase setting accuracy and associated operating speeds. It is also easy to set different values ​​for the prescribable phase offset, and this can advantageously be done at the software level. Thus, the same electronic unit and arrangement can be used for different prescribable phase offsets. The solution according to the present invention can also be advantageously used with both digital and analog versions of the corresponding oscillating circuit for exciting the vibratory unit and can be easily adapted to different sensors, in particular different vibratory units.

[0022] Quadrature demodulation itself is a modulation method known from the prior art, in which amplitude modulation and phase modulation are combined. Both analog and digital methods based on quadrature modulation are already known. In the combination of an electronic vibration sensor with an electronic unit and an adaptive filter, as is the case with the present invention, this solution offers the great advantage of achieving highly accurate detection of phase offsets, which are also independent of the corresponding signal amplitude. In many cases of variants used in conjunction with electronic vibration sensors (particularly those using the phase-locked principle), for example, rectangular signals are used in order to be independent of the signal amplitude in each case. However, this has the disadvantage that an undesirable additional phase offset can occur between the excitation signal and the received signal, which has a negative impact on the measurement accuracy.

[0023] In an embodiment of the electronic vibration sensor, the detection unit comprises a first and / or second reference unit for generating the first and / or second reference signal in order to perform a quadrature demodulation.

[0024] With regard to the first and / or second reference units, they are advantageously designed to generate the first and / or second reference signal based on the received signal.

[0025] With regard to the reference unit(s), it is further advantageous if one of the two reference units comprises a first phase shifter for generating one of the reference signals having a phase shift of + / -90° relative to the received signal. Advantageously, the first phase shifter is in particular a second adaptive filter, which is in particular identical in design to the first adaptive filter, an all-pass filter or a Hilbert transform.

[0026] It is also advantageous if the other of the two reference units comprises a second phase shifter for generating one of the reference signals with a phase shift of 0° relative to the received signal. The second phase shifter is advantageously a multiplier or an adaptive filter, in particular a resonator filter.

[0027] In one embodiment of the electronic vibration sensor, the electronics unit is designed to set a target phase offset by adjusting the center frequency of the adaptive filter, in particular with the aid of a phase control unit. The center frequency is thus varied so that a specific, predeterminable phase offset exists between the excitation signal and the received signal. Reference is made in this regard to DE 10 2014 119 061 A1.

[0028] In another embodiment of the electronic vibration sensor, the target phase shift is 90°, 45° or 0°. Although, depending on the embodiment of the sensor unit (particularly the drive / receiver unit), a prescribable phase shift of 90° or 0° may result in resonant excitation of the vibratory unit, a prescribable phase shift of + / - 45° may be preferred for determining density or viscosity.

[0029] A wide variety of filters can be used as the adaptive filter. Preferably, the first and / or second adaptive filter is a resonator filter or a bandpass filter, in particular a lowpass filter, in particular a second-order lowpass filter.

[0030] A further embodiment of the electronic vibration sensor according to the invention comprises that the electronic unit is designed to alternately execute a first operating mode and a second operating mode, wherein the driving / receiving unit is designed to excite mechanical vibrations in the mechanically vibratable unit by means of an electrical excitation signal during the first operating mode, wherein the electronic unit is designed to: during the second operating mode,

[0031] - interrupting the excitation of the mechanically vibratable unit by means of the excitation signal,

[0032] - receiving the mechanical vibration of the mechanically vibrating unit and converting it into an electrical reception signal,

[0033] - setting at least one value of a filter characteristic of the adaptive filter such that there is a specifiable phase offset between the excitation signal and the received signal, and

[0034] - determining at least one process variable based on the received signal.

[0035] In this regard, reference is made to DE 10 2016 111 134 A1.

[0036] During a first operating mode (hereinafter also referred to as an excitation sequence), mechanical vibrations are excited in the mechanically vibrable unit by means of a drive / receiver unit. During a second operating mode (also referred to as a measurement / control sequence), excitation of the vibrable unit is interrupted. Therefore, during the second operating mode, no electrical excitation signal is applied to the excitation / receiver unit. During the second operating mode, the vibrable unit continues to vibrate at its natural frequency in the form of damped vibrations. The vibrations are converted into an electrical receive signal, from which at least one process variable is determined, and the current phase offset between the excitation signal and the receive signal is controlled to a predeterminable value or a predeterminable phase offset by appropriately setting at least the filter characteristics. Thus, the excitation signal is generated based on the receive signal. A decisive advantage of this is that the mechanical vibrations in the form of the receive signal can be detected and evaluated independently of the excitation signal. This is particularly advantageous if, for example, coupling between the excitation signal and the receive signal occurs due to the design. This is the case, for example, if the excitation signal and the receive signal are superimposed.

[0037] Process variables include, for example, a fill level, in particular a specifiable fill level, or the density or viscosity of a medium in a container. The vibratory element of a vibratory electronic sensor can be designed, for example, in the form of a diaphragm, a single rod, or a vibrating fork. The drive / receiver element can, in particular, be an electromagnetic or piezoelectric drive / receiver element.

[0038] The object underlying the present invention is further achieved by a method for operating an electronic vibration sensor, in particular according to one of the described embodiments, for determining and / or monitoring at least one process variable of a medium in a container, wherein mechanical vibrations are excited in a mechanically vibratory unit by means of an electrical excitation signal, and the mechanical vibrations of the mechanically vibratory unit are received and converted into an electrical reception signal, wherein an excitation signal is generated based on the reception signal, and the at least one process variable is determined, and wherein the filter characteristic of the adaptive filter is set such that a target phase shift exists between the excitation signal and the reception signal. According to the invention, quadrature demodulation is used to determine the phase shift between the excitation signal and the reception signal and / or the amplitude of the reception signal.

[0039] The excitation signal may be a periodic signal, such as a triangular signal, a sinusoidal signal or a square wave signal. Preferably, when in the adjustment state, the vibratable unit performs resonant vibration in a fundamental mode.

[0040] The method according to the invention can also be used for digital and analog versions of the corresponding oscillating circuits for exciting the oscillating unit. Similarly, by using the method according to the invention, different phase setting accuracies can be achieved depending on the application, and different prescribable phase offsets can be set depending on the application.

[0041] The embodiments described in conjunction with the vibratory electronic sensor according to the invention can also be applied mutatis mutandis to the method according to the invention and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The following will refer to Figures 1 to 3 The present invention and its advantageous embodiments are described in more detail. They are shown below:

[0043] Figure 1 : Schematic diagram of an electronic vibration sensor according to the prior art,

[0044] Figure 2 : a block diagram of a first embodiment of an electronic unit according to the invention, and

[0045] Figure 3 : Block diagram of another embodiment of an electronic unit according to the present invention, used to illustrate the performance of two operating modes. DETAILED DESCRIPTION

[0046] Figure 1 A vibratory electronic sensor 1 is shown. A vibratory element 4 in the form of a vibrating fork is depicted, partially immersed in a medium 2 located in a container 3. An excitation / receiving unit 5 excites mechanical vibrations in the vibratory element, which can be, for example, a piezoelectric stack driver or a bimorph driver. However, it is naturally understood that other embodiments of the vibratory electronic sensor also fall within the scope of the present invention. Furthermore, an electronics unit 6 is shown, which performs signal detection, signal evaluation, and / or signal supply.

[0047] A block diagram of a first exemplary embodiment of an electronic unit according to the present invention is Figure 2 theme.

[0048] With the help of the excitation signal U A Mechanical vibrations are excited in the vibratable element 4. The received signal U representing these vibrations E Before being supplied to the first adaptive filter 7, it first passes through the analog / digital converter D / A. In continuous operation, the filter characteristic of the adaptive filter 7 is set so that the excitation signal U A and the received signal U E There is a specifiable phase offset Φ between soll =360°-Φ Filter , where Φ filter is the phase offset between the input signal and the output signal of the adaptive filter 7. The control unit 12 then appropriately controls the phase based on the phase offset ΔΦ detected in each case. soll For more details, please refer to DE102014119061A1.

[0049] By means of the detection unit 10, the received signal U is determined E The amplitude 11a and the excitation signal U A The phase offset 11b ΔΦ between the received signal and the received signal. According to the present invention, the detection unit 10 is designed to determine the phase offset ΔΦ using quadrature demodulation. This allows for a high degree of accuracy in this determination, which is also advantageously independent of the individual signal amplitudes. Before entering the detection unit 10, each input signal passes through a low-pass filter 9a, 9b, which is also selectable.

[0050] The detection of the phase ΔΦ by means of quadrature demodulation requires two reference signals R1, R2 which, in the embodiment shown here, are advantageously obtained from the received signal U E Advantageously, no additional signal source is required to generate the reference signals R1, R2. The reference signals R1 and R2 can be generated in a particularly simple manner. The first reference unit 8a is used to generate a reference signal relative to the received signal U E The first reference signal R1 is provided with a phase shift of +90°, and for this purpose, for example, the first reference unit 8a comprises here a second adaptive filter having the same design as the first adaptive filter 7. Alternatively, other elements having a different design from the first adaptive filter 7 can be used; for example, an adaptive bandpass filter can also be used. The first reference unit 8a can also include multiple components to generate a phase shift of + / -90°.

[0051] The second reference unit 8b is used to generate a reference signal relative to the received signal U E The second reference signal R2 has a 0° phase shift, and here the second reference unit 8b comprises a multiplier for this purpose. Furthermore, it should be noted that there are many other alternatives available that are familiar to a person skilled in the art.

[0052] Another exemplary embodiment of the electronic unit 6 according to the invention is Figure 3 For this embodiment, two different operating modes are implemented and the electronic unit 6 comprises a switching element 13 for switching back and forth between these two operating modes.

[0053] For the performance of the two operating modes, please refer to DE102016111134A1. In the first operating mode, also called the excitation sequence, the excitation signal U A is applied to the vibrating element 4 and causes mechanical vibration. Therefore, the vibrating element 4 stores vibration energy in this way. The received signal U from the vibrating element 4 E Superimposed on the excitation signal U A During the excitation sequence, no excitation signal UA and the received signal U E The current phase offset ΔΦ between φ and φ is actively measured or set. The filter characteristics of the adaptive filter 7 remain constant.

[0054] During the second operating mode 16 (also called measuring / control sequence), the application of the excitation signal U to the sensor units 4 , 5 is interrupted by means of the switching element 13 . A The vibratable unit 4 now vibrates at its natural resonance frequency f0 and accordingly performs a damped resonant vibration. A Now no longer superimposed on the received signal U E A suitable signal evaluation can thus be performed in an evaluation unit 14 of the electronic unit 6 designed for this purpose, which here has, for example, a digitally controlled oscillator DCO and a unit 15 for detecting zero crossings. A and the received signal U E For example, in order to control the current phase offset ΔΦ, the center frequency f of the adaptive filter 7 can be appropriately set to m Thus, during a continuous measurement / control sequence, various internal parameters used for control and phase measurement and / or the values ​​of these parameters are successively changed until, for example, a resonant excitation of the sensor units 4 , 5 occurs.

[0055] Reference Signs List

[0056] 1 Electronic vibration sensor

[0057] 2 Medium

[0058] 3 Containers

[0059] 4 Vibrating units

[0060] 5 Electromechanical converter unit

[0061] 6 Electronic units

[0062] 7 Adaptive Filter

[0063] Reference units 8, 8a, 8b

[0064] 9, 9a, 9b low-pass filters

[0065] 10 detection units

[0066] 11a, 11b detect amplitude (a) and phase (b)

[0067] 12 Control Unit

[0068] 13 Switching elements

[0069] 14 evaluation units

[0070] 15 units for detecting zero crossings

[0071] U A stimulus signal

[0072] U E Receive signal

[0073] f m Center frequency of the adaptive filter

[0074] f0 Resonant frequency of the vibrating unit

[0075] A l Amplitude

[0076] ΔΦ phase shift

[0077] Φ soll Specifiable phase offset between stimulus and received signals

[0078] Φ filter The phase shift between the input and output signals of the adaptive filter

Claims

1. An electronic vibration sensor (1) for determining and / or monitoring at least one process variable of a medium (2) in a container (3), said electronic vibration sensor (1) comprising at least a mechanically vibrable unit (4), a drive / receiving unit (5) and an electronic unit (6), in, The driving / receiving unit (5) is designed to: A ) excites the mechanical vibration in the mechanically vibrating unit (4), and receives the mechanical vibration of the mechanically vibrating unit (4) and converts the mechanical vibration into an electrical receiving signal (U E ), Wherein, the electronic unit (6) is designed to: based on the received signal (U E ) generates the excitation signal (U A ), and according to the received signal (U E ) determining the at least one process variable, and The electronic unit (6) includes a first adaptive filter (7), and the electronic unit (6) is designed to set the filter characteristics of the first adaptive filter (7) so that the excitation signal (U A ) and the received signal (U E ) produces a target phase shift (ΔΦ soll ), It is characterized in that The electronic vibration sensor has a detection unit (10) designed to determine the excitation signal (U A ) and the phase shift (ΔΦ) between the received signal and / or the received signal (U E ), The detection unit (10) includes a first reference unit (8a) and a second reference unit (8b), wherein the first reference unit (8a) and the second reference unit (8b) are used to generate a first reference signal (R1) and / or a second reference signal (R2) in order to perform the orthogonal demodulation. One of the two reference units (8) comprises a first phase shifter, wherein the first phase shifter is used to generate a phase shift relative to the received signal (U E ) one of the reference signals (R) with a phase shift of + / -90°, wherein the first phase shifter is a second adaptive filter or an all-pass filter or a Hilbert transform, and / or One of the two reference units (8) includes a second phase shifter, the second phase shifter is used to generate a phase shift relative to the received signal (U E ) one of the reference signals (R) with a phase shift of 0°, The second phase shifter is a multiplier or an adaptive filter.

2. The electronic vibration sensor (1) according to claim 1, in, The first reference unit (8a) and the second reference unit (8b) are designed to be based on the received signal (U E ) generates the first reference signal (R1) and the second reference signal (R2).

3. The electronic vibration sensor (1) according to claim 1 or 2, in, The second adaptive filter has the same design as the first adaptive filter (7).

4. The electronic vibration sensor (1) according to claim 1 or 2, in, The second phase shifter is a resonator filter.

5. The electronic vibration sensor (1) according to claim 1 or 2, in, The electronic unit (6) is designed to adjust the center frequency (f m ) to set the target phase offset (ΔΦ soll ).

6. The electronic vibration sensor (1) according to claim 1 or 2, in, The first adaptive filter (7) and / or the second adaptive filter is a resonator filter or a bandpass filter.

7. The electronic vibration sensor (1) according to claim 1 or 2, in, The first adaptive filter (7) and / or the second adaptive filter is a low-pass filter.

8. The electronic vibration sensor (1) according to claim 1 or 2, in, The first adaptive filter (7) and / or the second adaptive filter is a second-order low-pass filter.

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