Vibration wire sensor anti-interference circuit and device

Abstract

The invention relates to the technical field of sensor signal processing, in particular to a vibrating wire sensor anti-interference circuit and device, and the circuit comprises an interference suppression circuit, a differential amplification circuit, a clamping circuit, a low-pass filter circuit, a zero cross detection circuit and a processing module. The input end of the interference suppression circuit is used for being connected with a vibrating wire sensor, the output end of the interference suppression circuit is connected to the input end of the differential amplification circuit, the output end of the differential amplification circuit is connected to the input end of the clamping circuit, the output end of the clamping circuit is connected to the input end of the low-pass filtering circuit, and the output end of the low-pass filtering circuit is connected to the input end of the vibration wire sensor. The output end of the low-pass filter circuit is connected to the input end of the zero-cross detection circuit, and the output end of the zero-cross detection circuit is connected to the processing module. According to the invention, interference signals can be removed so as to obtain accurate signals to be detected.

Description

Technical Field

[0001] The present application relates to the technical field of sensor signal processing, and in particular to an anti-interference circuit and device for a vibrating string sensor. Background Art

[0002] With the development of electronic technology, various sensors have been designed. As one of the sensors, vibrating string sensors are used in hydropower stations to detect dams.

[0003] In actual use, the signal to be tested detected and output by the vibrating string sensor may jump, that is, the signal to be tested is mixed with interference signals, resulting in an inaccurate signal finally obtained, thus resulting in an inaccurate detection result. Therefore, how to process the signal to obtain an accurate signal to be tested has become an urgent problem to be solved. Summary of the invention

[0004] In order to remove interference signals to obtain accurate signals to be measured, the present application provides an anti-interference circuit and device for a vibrating-string sensor.

[0005] In the first aspect, the present application provides a vibrating string sensor anti-interference circuit adopting the following technical solution: A vibrating string sensor anti-interference circuit comprises an interference suppression circuit, a differential amplifier circuit, a clamp circuit, a low-pass filter circuit, a zero-crossing detection circuit and a processing module; the input end of the interference suppression circuit is used to connect the vibrating string sensor, the output end of the interference suppression circuit is connected to the input end of the differential amplifier circuit, the output end of the differential amplifier circuit is connected to the input end of the clamp circuit, the output end of the clamp circuit is connected to the input end of the low-pass filter circuit, the output end of the low-pass filter circuit is connected to the input end of the zero-crossing detection circuit, and the output end of the zero-crossing detection circuit is connected to the processing module.

[0006] By adopting the above technical scheme, the interference suppression circuit receives the signal to be tested transmitted by the vibrating string sensor, can protect the subsequent circuit when encountering a surge current caused by lightning, can avoid the influence of different lengths of the vibrating string sensor connecting cables, different input capacitors and line imbalance on the working characteristics of this circuit, can filter out high-frequency noise, attenuate the amplitude of the common-mode signal, and can also prevent the generation of signal tailing; the differential amplifier circuit is used to amplify the differential-mode signal to avoid the attenuated common-mode signal from being converted into a differential-mode signal; the clamping circuit is used to clamp the high-frequency signal with a large amplitude to prevent the subsequent circuit from saturating; the low-pass filter circuit is used to extract the low-frequency signal, attenuate the high-frequency signal, and adjust the signal to be tested to an amplitude suitable for detection; the zero-crossing detection circuit is used to convert the bipolar sine wave signal to be tested into a unipolar square wave signal that can be recognized by the processing module. The interference signal in the signal to be tested is filtered out, so as to obtain a more accurate signal to be tested, and then the detection result is more accurate.

[0007] Optionally, the interference suppression circuit includes a first filtering circuit and a suppression circuit, the first filtering circuit is connected to the input end of the interference suppression circuit, the first filtering circuit is also connected to the suppression circuit, and the suppression circuit is also connected to the output end of the interference suppression circuit.

[0008] Optionally, the first filtering circuit includes a resistor R16, a resistor R11, a resistor R23, a resistor R26, a resistor R17, a capacitor C7, a capacitor C12, a capacitor C16, a capacitor C17, an output terminal A and an output terminal B, the input terminal of the interference suppression circuit includes an input terminal V1 and an input terminal V2, the input terminal V1 is connected to the resistor R16, the other end of the resistor R16 is connected to the output terminal A, the input terminal V2 is connected to the resistor R26, the other end of the resistor R26 is connected to the output terminal B, one end of the capacitor C16 is connected to the input terminal V1, the other end of the capacitor C16 is connected to the capacitor C17, and the other end of the capacitor C17 is connected to the output terminal A. The input terminal V2, one end of the capacitor C7 is connected to the output terminal A, the other end of the capacitor C7 is connected to the capacitor C12, the other end of the capacitor C12 is connected to the output terminal B, one end of the resistor R11 is connected to the output terminal A, the other end of the resistor R11 is connected to the resistor R23, the other end of the resistor R23 is connected to the output terminal B, a connection point X1 between the capacitor C16 and the capacitor C17 is short-circuited with a connection point X2 between the capacitor C7 and the capacitor C12, a connection point X3 between the resistor R11 and the resistor R23 is short-circuited with the connection point X2, one end of the resistor R17 is connected to the connection point X3, and the other end of the resistor R17 is connected to the ground terminal.

[0009] By adopting the above technical solution, the components in the first filter circuit form a π-type filter circuit, which can solve the influence of different lengths of the cables connecting the vibrating string sensor, different input capacitors and line imbalance on the working characteristics of the circuit, that is, it can reduce the interference signal in the signal to be measured; by setting the resistor R17, the current to the ground can be limited when the vibrating string sensor encounters a lightning strike and generates a surge current, thereby protecting the subsequent circuit.

[0010] Optionally, the suppression circuit includes a resistor R8, a resistor R24, a capacitor C5, a capacitor C14 and a common-mode inductor L1, the output end of the interference suppression circuit includes an output end W1 and an output end W2, pin 1 of the common-mode inductor L1 is connected to the output end A, pin 2 of the common-mode inductor L2 is connected to the output end B, one end of the resistor R8 is connected to the ground end, the other end of the resistor R8 is connected to pin 4 of the common-mode inductor L1, the capacitor C5 is connected in parallel with the resistor R8, one end of the resistor R24 ​​is connected to the ground end, the other end of the resistor R24 ​​is connected to pin 3 of the common-mode inductor L1, the capacitor C14 is connected in parallel with the resistor R24, pin 4 of the common-mode inductor L1 is connected to the output end W1, and pin 3 of the common-mode inductor L1 is connected to the output end W2.

[0011] By adopting the above technical solution, the suppression circuit composed of the common-mode inductor L1, capacitors and resistors can filter out high-frequency noise, attenuate the common-mode signal amplitude, and prevent the common-mode signal amplitude from being too large and prevent the signal from generating tailing.

[0012] Optionally, the differential amplifier circuit includes a resistor R14, a resistor R3, a resistor R20, a resistor R25, a capacitor C4, a capacitor C10 and an operational amplifier U2, one end of the resistor R14 is used to connect to the input end of the differential amplifier circuit, the other end of the resistor R14 is connected to the non-inverting input end of the operational amplifier U2, one end of the resistor R3 is connected to the ground end, the other end of the resistor R3 is connected to the non-inverting input end of the operational amplifier U2, the positive terminal of the operational amplifier U2 is connected to the power supply end AVCC, one end of the capacitor C4 is connected to the power supply end AVCC, and the other end of the capacitor C4 is connected to the ground end. The negative terminal of the operational amplifier U2 is connected to the ground terminal, one end of the resistor R20 is used to connect the input terminal of the differential amplifier circuit, the other end of the resistor R20 is connected to the inverting input terminal of the operational amplifier U2, the negative terminal of the operational amplifier U2 is connected to the power supply terminal AVCC-, one end of the capacitor C10 is connected to the ground terminal, the other end of the capacitor C10 is connected to the power supply terminal AVCC-, one end of the resistor R25 is connected to the inverting input terminal of the operational amplifier U2, the other end of the resistor R25 is connected to the output terminal of the operational amplifier U2, and the output terminal of the operational amplifier U2 is used to connect the output terminal of the differential amplifier circuit.

[0013] Optionally, the clamping circuit includes a resistor R12, a resistor R18, a resistor R5, a resistor R22, a capacitor C15, a transistor Q1, a transistor Q3 and an operational amplifier U1, one end of the resistor R12 is used to connect to the input end of the clamping circuit, the other end of the resistor R12 is connected to the inverting input end of the operational amplifier U1, one end of the resistor R18 is used to connect to the input end of the clamping circuit, the other end of the resistor R18 is connected to the non-inverting input end of the operational amplifier U1, one end of the resistor R22 is connected to the capacitor C15, the other end of the resistor R22 is connected to the non-inverting input end of the operational amplifier U1, and the capacitor C15 is connected to the inverting input end of the operational amplifier U1. The other end is connected to the ground end, one end of the resistor R5 is connected to the inverting input end of the operational amplifier U1, the other end of the resistor R5 is connected to the output end of the operational amplifier U1, the base of the transistor Q3 is connected to the inverting input end of the operational amplifier U1, the collector and the base of the transistor Q3 are short-circuited, the emitter of the transistor Q3 is connected to the output end of the operational amplifier U1, the emitter of the transistor Q1 is connected to the inverting input end of the operational amplifier U1, the collector of the transistor Q1 is connected to the output end of the operational amplifier U1, the base and the collector of the transistor Q1 are short-circuited, and the output end of the operational amplifier U1 is used to connect the output end of the clamping circuit.

[0014] By adopting the above technical solution, resistor R12 can provide a large bias working current for the triode, and setting resistor R18 can make the impedance of the two input terminals of the operational amplifier U1 match. At the same time, resistor R18, resistor R22 and capacitor form a low-pass filter to extract low-frequency signals and attenuate high-frequency signals; resistor R22 improves the phase of low-frequency signals and reduces signal delay. In addition, the clamping circuit can clamp high-frequency signals with large amplitudes to prevent saturation of subsequent circuits.

[0015] Optionally, the low-pass filter circuit includes a resistor R1, a resistor R9, a resistor R10, a resistor R15, a resistor R21, a capacitor C1, a capacitor C3, a capacitor C6, a capacitor C9, a capacitor C13 and an operational amplifier U3, one end of the resistor R15 is used to connect to the input end of the low-pass filter circuit, the other end of the resistor R15 is connected to the inverting input end of the operational amplifier U3, one end of the resistor R9 is used to connect to the input end of the low-pass filter circuit, the other end of the resistor R9 is connected to the resistor R10, the other end of the resistor R10 is connected to the non-inverting input end of the operational amplifier U3, one end of the capacitor C6 is connected to the connection point of the resistor R9 and the resistor R10, the other end of the capacitor C6 is connected to the ground end, and one end of the resistor R1 is also connected to the resistor R9 and the resistor R1 0, the other end of the resistor R1 is connected to the output end of the operational amplifier U3, one end of the capacitor C1 is connected to the non-inverting input end of the operational amplifier U3, the other end of the capacitor C1 is connected to the output end of the operational amplifier U3, one end of the resistor R21 is connected to the inverting input end of the operational amplifier U3, the other end of the resistor R21 is connected to the capacitor C13, the other end of the capacitor C13 is connected to the ground end, the positive end of the operational amplifier U3 is connected to the power supply end AVCC, one end of the capacitor C3 is connected to the power supply end AVCC, the negative end of the operational amplifier U3 is connected to the power supply end AVCC-, one end of the capacitor C9 is connected to the power supply end AVCC-, the other end of the capacitor C9 is connected to the ground end, and the output end of the operational amplifier U3 is used to connect the output end of the low-pass filter circuit.

[0016] Optionally, the zero-crossing detection circuit includes a resistor R2, a resistor R7, a resistor R6, a resistor R4, a resistor R13, a resistor R19, a capacitor C2, a capacitor C8, a capacitor C9, a capacitor C11, a MOS tube Q2 and a comparator U4, one end of the resistor R7 is used to connect to the input end of the zero-crossing detection circuit, the other end of the resistor R7 is connected to the non-inverting input end of the comparator U4, one end of the resistor R13 is used to connect to the input end of the zero-crossing detection circuit, the other end of the resistor R13 is connected to the reverse input end of the comparator U4, one end of the resistor R19 is connected to the inverting input end of the comparator U4, the other end of the resistor R19 is connected to the capacitor C11, the other end of the capacitor C11 is connected to the ground end, one end of the resistor R2 is connected to the non-inverting input end of the comparator U4, the other end of the resistor R2 is connected to the output end of the comparator U4, and the comparator The positive terminal of U4 is connected to the power supply terminal AVCC, one end of the capacitor C2 is connected to the power supply terminal AVCC, and the other end of the capacitor C2 is connected to the ground terminal. The negative terminal of the comparator U4 is connected to the power supply terminal AVCC-, one end of the capacitor C8 is connected to the power supply segment AVCC-, and the other end of the capacitor C8 is connected to the ground terminal. One end of the resistor R6 is connected to the output end of the comparator U4, and the other end of the resistor R6 is connected to the power supply terminal AVCC. One end of the capacitor C9 is connected to the output end of the comparator U4, and the other end of the capacitor C9 is connected to the ground terminal. The gate of the MOS tube Q2 is connected to the output end of the comparator U4, the source of the MOS tube Q2 is connected to the ground terminal, the drain of the MOS tube Q2 is connected to the resistor R4, and the other end of the resistor R4 is connected to the power supply terminal DVCC. The drain of the MOS tube Q2 is also used to connect the output end of the zero-crossing detection circuit.

[0017] By adopting the above technical solution, the resistor R7 and the resistor R2 are used to set the hysteresis of the comparator U4 to eliminate the situation where the comparator U4 generates an abnormal flip signal due to the jitter of the comparison signal. The capacitor C9 increases the junction capacitance between the gate and the source of the MOS tube Q2 to eliminate the spike pulse generated at the moment when the MOS tube Q2 is turned on, and the zero-crossing detection circuit can convert the bipolar sine wave into a unipolar square wave signal that can be recognized by the processing module.

[0018] In the second aspect, the present application provides a vibrating string sensor anti-interference device adopts the following technical solution: A vibrating string sensor anti-interference device comprises a vibrating string sensor anti-interference circuit as described in the first aspect.

[0019] In summary, the present application includes at least one of the following beneficial technical effects: 1. The interference suppression circuit receives the signal to be tested transmitted by the vibrating-string sensor, and can protect the subsequent circuit when a surge current is generated by lightning. It can avoid the influence of different lengths of the cables connecting the vibrating-string sensor, different input capacitors and line imbalance on the working characteristics of this circuit, and can filter out high-frequency noise, attenuate the amplitude of the common-mode signal, and prevent the generation of signal tailing; the differential amplifier circuit is used to amplify the differential-mode signal to avoid the attenuated common-mode signal from being converted into a differential-mode signal; the clamping circuit is used to clamp high-frequency signals with large amplitudes to prevent saturation of the subsequent circuits; the low-pass filter circuit is used to extract low-frequency signals, attenuate high-frequency signals, and adjust the signal to be tested to an amplitude suitable for detection; the zero-crossing detection circuit is used to convert the bipolar sine wave signal to be tested into a unipolar square wave signal that can be recognized by the processing module. The interference signal in the signal to be tested is filtered out, so as to obtain a more accurate signal to be tested, and thus the detection result is more accurate; 2. The components in the first filter circuit form a π-type filter circuit, which can solve the influence of different lengths of the vibrating string sensor connection cables, different input capacitors and line imbalance on the working characteristics of this circuit, that is, it can reduce the interference signal in the signal to be measured; by setting the resistor R17, the ground current can be limited when the vibrating string sensor encounters a lightning strike and generates a surge current, thereby protecting the subsequent circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a connection block diagram showing the entire embodiment.

[0021] Figure 2 is a circuit schematic diagram showing the interference suppression circuit of this embodiment.

[0022] Figure 3 is a circuit schematic diagram showing the differential amplifier circuit of this embodiment.

[0023] Figure 4 is a circuit schematic diagram showing the clamping circuit of this embodiment.

[0024] Figure 5 is a circuit schematic diagram showing the low-pass filter circuit of this embodiment.

[0025] Figure 6 is a circuit schematic diagram showing the zero-crossing detection circuit of this embodiment.

[0026] Explanation of the accompanying drawings: 1. Interference suppression circuit; 11. First filtering circuit; 12. Suppression circuit; 2. Differential amplifier circuit; 3. Clamping circuit; 4. Low-pass filtering circuit; 5. Zero-crossing detection circuit; 6. Processing module. DETAILED DESCRIPTION

[0027] The following is combined with Figure 1-6 This application is described in further detail.

[0028] The present application embodiment discloses a vibrating wire sensor anti-interference circuit. Figure 1 , an anti-interference circuit of a vibrating string sensor comprises an interference suppression circuit 1, a differential amplifier circuit 2, a clamp circuit 3, a low-pass filter circuit 4, a zero-crossing detection circuit 5 and a processing module 6. The input end of the interference suppression circuit 1 is used to connect the vibrating string sensor, the output end of the interference suppression circuit 1 is connected to the input end of the differential amplifier circuit 2, the output end of the differential amplifier circuit 2 is connected to the input end of the clamp circuit 3, the output end of the clamp circuit 3 is connected to the input end of the low-pass filter circuit 4, the output end of the low-pass filter circuit 4 is connected to the input end of the zero-crossing detection circuit 5, and the output end of the zero-crossing detection circuit 5 is connected to the processing module 6.

[0029] Reference Figure 2 The interference suppression circuit 1 includes a first filtering circuit 11 and a suppression circuit 12. The first filtering circuit 11 is connected to the input end of the interference suppression circuit 1. The first filtering circuit 11 is also connected to the suppression circuit 12. The suppression circuit 12 is also connected to the output end of the interference suppression circuit 1.

[0030] Specifically, the first filtering circuit 11 includes a resistor R16, a resistor R11, a resistor R23, a resistor R26, a resistor R17, a capacitor C7, a capacitor C12, a capacitor C16, a capacitor C17, an output terminal A and an output terminal B. The input terminal of the interference suppression circuit 1 includes an input terminal V1 and an input terminal V2. The input terminal V1 is connected to the resistor R16, and the other end of the resistor R16 is connected to the output terminal A. The input terminal V2 is connected to the resistor R26, and the other end of the resistor R26 is connected to the output terminal B. One end of the capacitor C16 is connected to the input terminal V1, and the other end of the capacitor C16 is connected to the capacitor C17. The other end of the capacitor C17 is connected to the input terminal V1. One end is connected to the input terminal V2, one end of the capacitor C7 is connected to the output terminal A, the other end of the capacitor C7 is connected to the capacitor C12, the other end of the capacitor C12 is connected to the output terminal B, one end of the resistor R11 is connected to the output terminal A, the other end of the resistor R11 is connected to the resistor R23, the other end of the resistor R23 is connected to the output terminal B, a connection point X1 between the capacitor C16 and the capacitor C17 is short-circuited with a connection point X2 between the capacitor C7 and the capacitor C12, a connection point X3 between the resistor R11 and the resistor R23 is short-circuited with the connection point X2, one end of the resistor R17 is connected to the connection point X3, and the other end of the resistor R17 is connected to the ground terminal.

[0031] The components in the first filter circuit 11 form a π-type filter circuit, which is used to solve the influence of different lengths of cables connected to the external vibrating string sensor, different input capacitors and line imbalance on the operation of the circuit, that is, to improve the accuracy of the signal. In addition, by setting the resistor R17, the magnitude of the ground current can be limited when the vibrating string sensor encounters a surge current such as a lightning strike, thereby protecting the subsequent circuit.

[0032] The suppression circuit 12 includes a resistor R8, a resistor R24, a capacitor C5, a capacitor C14 and a common-mode inductor L1. The output end of the interference suppression circuit 1 includes an output end W1 and an output end W2. Pin 1 of the common-mode inductor L1 is connected to the output end A, and pin 2 of the common-mode inductor L2 is connected to the output end B. One end of the resistor R8 is connected to the ground end, and the other end of the resistor R8 is connected to pin 4 of the common-mode inductor L1. The capacitor C5 is connected in parallel with the resistor R8, one end of the resistor R24 ​​is connected to the ground end, and the other end of the resistor R24 ​​is connected to pin 3 of the common-mode inductor L1. The capacitor C14 is connected in parallel with the resistor R24, and pin 4 of the common-mode inductor L1 is connected to the output end W1, and pin 3 of the common-mode inductor L1 is connected to the output end W2.

[0033] The common-mode inductor L1, resistor and capacitor form a suppression circuit 12 for filtering high-frequency noise in the circuit, and can attenuate the common-mode signal amplitude, reduce the possibility of the common-mode signal amplitude exceeding the maximum common-mode voltage allowed by the subsequent circuit, and avoid signal tailing.

[0034] Reference Figure 3 The differential amplifier circuit 2 includes a resistor R14, a resistor R3, a resistor R20, a resistor R25, a capacitor C4, a capacitor C10 and an operational amplifier U2. One end of the resistor R14 is used to connect the input end of the differential amplifier circuit 2, that is, connected to the output end W1. The other end of the resistor R14 is connected to the non-inverting input end of the operational amplifier U2. One end of the resistor R3 is connected to the ground end. The other end of the resistor R3 is connected to the non-inverting input end of the operational amplifier U2. The positive terminal of the operational amplifier U2 is connected to the power supply end AVCC. One end of the capacitor C4 is connected to the power supply end AVCC. The other end of the capacitor C4 is connected to the power supply end AVCC. The first end of the differential amplifier circuit 2 is connected to the ground terminal, one end of the resistor R20 is used to connect the input terminal of the differential amplifier circuit 2, that is, connected to the output terminal W2, the other end of the resistor R20 is connected to the inverting input terminal of the operational amplifier U2, the negative terminal of the operational amplifier U2 is connected to the power supply terminal AVCC-, one end of the capacitor C10 is connected to the ground terminal, the other end of the capacitor C10 is connected to the power supply terminal AVCC-, one end of the resistor R25 is connected to the inverting input terminal of the operational amplifier U2, the other end of the resistor R25 is connected to the output terminal of the operational amplifier U2, and the output terminal of the operational amplifier U2 is used to connect the output terminal of the differential amplifier circuit 2.

[0035] The differential amplifier circuit 2 can suppress the attenuated common mode signal and amplify the differential mode signal. The operational amplifier U2 can avoid widening the interfering narrow pulse, thereby increasing the possibility of filtering out the interfering narrow pulse in the subsequent circuit. The differential amplifier circuit 2 can also avoid the attenuated common mode signal from being converted into a differential mode signal. The resistor in the differential amplifier circuit 2 uses a resistor with an accuracy of not less than one thousandth.

[0036] Reference Figure 4 The clamp circuit 3 includes a resistor R12, a resistor R18, a resistor R5, a resistor R22, a capacitor C15, a transistor Q1, a transistor Q3 and an operational amplifier U1. One end of the resistor R12 is used to connect the input end of the clamp circuit 3, that is, connected to the output end of the operational amplifier U2. The other end of the resistor R12 is connected to the inverting input end of the operational amplifier U1. One end of the resistor R18 is used to connect the input end of the clamp circuit 3, that is, also connected to the output end of the operational amplifier U2. The other end of the resistor R18 is connected to the non-inverting input end of the operational amplifier U1. One end of the resistor R22 is connected to the capacitor C15, and the other end of the resistor R22 is connected to the inverting input end of the operational amplifier U1. The same-phase input terminal of the operational amplifier U1 is connected to the non-inverting input terminal of the operational amplifier U1, the other end of the capacitor C15 is connected to the ground terminal, one end of the resistor R5 is connected to the inverting input terminal of the operational amplifier U1, the other end of the resistor R5 is connected to the output terminal of the operational amplifier U1, the base of the transistor Q3 is connected to the inverting input terminal of the operational amplifier U1, the collector and the base of the transistor Q3 are short-circuited, the emitter of the transistor Q3 is connected to the output terminal of the operational amplifier U1, the emitter of the transistor Q1 is connected to the inverting input terminal of the operational amplifier U1, the collector of the transistor Q1 is connected to the output terminal of the operational amplifier U1, the base and the collector of the transistor Q1 are short-circuited, and the output terminal of the operational amplifier U1 is used to connect the output terminal of the clamping circuit 3.

[0037] Among them, the transistor Q1 and the transistor Q3 are both PNP transistors made of germanium.

[0038] Connecting resistor R12 in series with the inverting input of operational amplifier U1 can provide a larger biased operating current for the transistor, thereby increasing the speed of the transistor's conduction and cutoff; connecting resistor R18 in series with the non-inverting input of operational amplifier U1 can match the input impedance of operational amplifier U1, so that operational amplifier U1 works under relatively ideal conditions. At the same time, resistor R18, resistor R22 and capacitor C15 form a low-pass filter, which can extract low-frequency signals and attenuate high-frequency signals. The signal at the non-inverting input of operational amplifier U1 is subtracted from the signal at the inverting input, which can eliminate the influence of the low-frequency signal on the signal to be measured. Resistor R22 can improve the phase of the low-frequency signal and reduce the signal delay. When the signal to be measured is at a high frequency of 5000Hz, the delay will not affect the measurement of the signal. The signal difference between the signal at the non-inverting input of operational amplifier U1 and the signal at the reverse input is amplified and clamped by the transistor to clamp the high-frequency signal with a large amplitude, preventing the saturation of the operational amplifier in the subsequent circuit.

[0039] The signal to be measured is the signal detected by the vibrating string sensor, that is, the required signal.

[0040] Reference Figure 5The low-pass filter circuit 4 includes a resistor R1, a resistor R9, a resistor R10, a resistor R15, a resistor R21, a capacitor C1, a capacitor C3, a capacitor C6, a capacitor C9, a capacitor C13 and an operational amplifier U3. One end of the resistor R15 is used to connect to the input end of the low-pass filter circuit 4, that is, connected to the output end of the operational amplifier U1. The other end of the resistor R15 is connected to the non-inverting input end of the operational amplifier U3. One end of the resistor R9 is used to connect to the input end of the low-pass filter circuit 4, that is, connected to the output end of the operational amplifier U1. The other end of the resistor R9 is connected to the resistor R10. The other end of the resistor R10 is connected to the inverting input end of the operational amplifier U3. One end of the capacitor C6 is connected to the connection point of the resistor R9 and the resistor R10. The other end of the capacitor C6 is connected to the ground end. One end of the resistor R1 is also connected to the resistor R1. At the connection point of resistor R9 and resistor R10, the other end of resistor R1 is connected to the output end of operational amplifier U3, one end of capacitor C1 is connected to the inverting input end of operational amplifier U3, the other end of capacitor C1 is connected to the output end of operational amplifier U3, one end of resistor R21 is connected to the non-inverting input end of operational amplifier U3, the other end of resistor R21 is connected to capacitor C13, the other end of capacitor C13 is connected to the ground end, the positive end of operational amplifier U3 is connected to the power supply end AVCC, one end of capacitor C9 is connected to the power supply end AVCC, the other end of capacitor C9 is connected to the ground end, the negative end of operational amplifier U3 is connected to the power supply end AVCC-, one end of capacitor C3 is connected to the power supply end AVCC-, the other end of capacitor C3 is connected to the ground end, and the output end of operational amplifier U3 is used to connect the output end of low-pass filter circuit 4.

[0041] Resistor R15, resistor R21 and capacitor C13 form a low-pass filter to extract low-frequency signals and attenuate high-frequency signals. Resistor R21 can improve the phase of low-frequency signals and reduce signal delay. When the signal to be measured is at a high frequency of 5000Hz, the delay will not affect the signal measurement. The corresponding setting of resistor R10 can achieve impedance matching at the input end of the operational amplifier U3. The signal difference between the in-phase input terminal signal and the inverting input terminal signal of the operational amplifier U3 is adjusted to the amplitude suitable for detection through a multi-stage feedback low-pass filter circuit.

[0042] The operational amplifier U1 and the operational amplifier U3 are integrated, that is, two operational amplifiers are included in the same IC package module. When the operational amplifier U3 is powered, the operational amplifier U1 is also powered, so the power supply end of the operational amplifier U1 in the figure is not connected to the power supply.

[0043] Reference Figure 6The zero-crossing detection circuit 5 includes a resistor R2, a resistor R7, a resistor R6, a resistor R4, a resistor R13, a resistor R19, a capacitor C2, a capacitor C8, a capacitor C9, a capacitor C11, a MOS tube Q2 and a comparator U4. One end of the resistor R7 is used to connect the input end of the zero-crossing detection circuit 5, that is, connected to the output end of the operational amplifier U3. The other end of the resistor R7 is connected to the non-inverting input end of the comparator U4. One end of the resistor R13 is used to connect the input end of the zero-crossing detection circuit 5, that is, connected to the output end of the operational amplifier U3. The other end of the resistor R13 is connected to the reverse input end of the comparator U4. One end of the resistor R19 is connected to the inverting input end of the comparator U4. The other end of the resistor R19 is connected to the capacitor C11. The other end of the capacitor C11 is connected to the ground. One end of the resistor R2 is connected to the non-inverting input end of the comparator U4. The other end of the resistor R2 is connected to the ground. The output end of the comparator U4, the positive end of the comparator U4 is connected to the power supply end AVCC, one end of the capacitor C2 is connected to the power supply end AVCC, the other end of the capacitor C2 is connected to the ground end, the negative end of the comparator U4 is connected to the power supply end AVCC-, one end of the capacitor C8 is connected to the power supply segment AVCC-, the other end of the capacitor C8 is connected to the ground end, one end of the resistor R6 is connected to the output end of the comparator U4, the other end of the resistor R6 is connected to the power supply end AVCC, one end of the capacitor C9 is connected to the output end of the comparator U4, the other end of the capacitor C9 is connected to the ground end, the gate of the MOS tube Q2 is connected to the output end of the comparator U4, the source of the MOS tube Q2 is connected to the ground end, the drain of the MOS tube Q2 is connected to the resistor R4, the other end of the resistor R4 is connected to the power supply end DVCC, and the drain of the MOS tube Q2 is also used to connect to the output end of the zero-crossing detection circuit 5, that is, connected to the processing module 6.

[0044] in, Figure 6 A transient suppression diode is short-circuited between the gate and the source of the MOS tube Q2. The transient suppression diode belongs to the MOS tube Q2, that is, the transient suppression diode is integrated in the MOS tube Q2.

[0045] The resistor R13, the resistor R19 and the capacitor C11 in the zero-crossing detection circuit 5 form a low-pass filter, which is used to attenuate the high-frequency signal in the signal to be measured and use it as the comparator reference signal. The comparator reference signal changes in real time with the low-frequency signal of the signal to be measured. The resistor R7 and the resistor R2 are used to set the hysteresis of the comparator U4 to eliminate the abnormal flip signal generated by the comparator U4 due to the jitter of the comparison signal. The capacitor C9 increases the junction capacitance between the gate and the source of the MOS tube Q2, which is used to eliminate the spike pulse generated at the moment when the MOS tube Q2 is turned on, and realizes the conversion of the bipolar sine wave signal to be measured into a unipolar square wave signal. The transient suppression diode in the MOS tube Q2 is used to prevent the components from being broken down due to static electricity, and plays a protective role.

[0046] The converted square wave signal, i.e., the signal to be tested, is transmitted to the processing module 6. The processing module 6 receives all the signals and sorts the received signals from small to large based on the pulse period. Then, the processing module 6 calculates the first average value of the middle period of the signal to be tested, sets the threshold to 10% to 20% of the first average value, filters out all periods exceeding the threshold, and then the processing module 6 calculates the second average value of the remaining periods of the signal to be tested, thereby obtaining a high-precision measurement value of the signal to be tested.

[0047] Based on the above circuit, a high-pass filtering effect is achieved through three-stage low-pass filtering subtraction operation, which can attenuate the 50Hz interference signal by 40db.

[0048] Through the circuit combination of this embodiment, the interference signal in the signal to be tested can be filtered out to a large extent, the generation of new interference signals can be reduced, and the signal to be tested can be made more consistent with the detection range, and finally a more accurate detection result can be obtained.

[0049] An embodiment of the present application further discloses an anti-interference device for a vibrating string sensor, and the anti-interference device for a vibrating string sensor includes the above-mentioned anti-interference circuit for a vibrating string sensor.

[0050] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A vibrating wire sensor anti-interference circuit, characterized in that: The invention comprises an interference suppression circuit (1), a differential amplifier circuit (2), a clamp circuit (3), a low-pass filter circuit (4), a zero-crossing detection circuit (5) and a processing module (6); the input end of the interference suppression circuit (1) is used to connect to a vibrating string sensor, the output end of the interference suppression circuit (1) is connected to the input end of the differential amplifier circuit (2), the output end of the differential amplifier circuit (2) is connected to the input end of the clamp circuit (3), the output end of the clamp circuit (3) is connected to the input end of the low-pass filter circuit (4), the output end of the low-pass filter circuit (4) is connected to the input end of the zero-crossing detection circuit (5), and the output end of the zero-crossing detection circuit (5) is connected to the processing module (6).

2. The anti-interference circuit of a vibrating wire sensor according to claim 1, characterized in that: The interference suppression circuit (1) comprises a first filtering circuit (11) and a suppression circuit (12); the first filtering circuit (11) is connected to an input end of the interference suppression circuit (1); the first filtering circuit (11) is also connected to the suppression circuit (12); and the suppression circuit (12) is also connected to an output end of the interference suppression circuit (1).

3. The anti-interference circuit of a vibrating wire sensor according to claim 2, characterized in that: The first filtering circuit (11) comprises a resistor R16, a resistor R11, a resistor R23, a resistor R26, a resistor R17, a capacitor C7, a capacitor C12, a capacitor C16, a capacitor C17, an output terminal A and an output terminal B. The input terminal of the interference suppression circuit (1) comprises an input terminal V1 and an input terminal V2. The input terminal V1 is connected to the resistor R16. The other end of the resistor R16 is connected to the output terminal A. The input terminal V2 is connected to the resistor R26. The other end of the resistor R26 is connected to the output terminal B. One end of the capacitor C16 is connected to the input terminal V1. The other end of the capacitor C16 is connected to the capacitor C17. The other end of the capacitor C17 is connected to the The input terminal V2, one end of the capacitor C7 is connected to the output terminal A, the other end of the capacitor C7 is connected to the capacitor C12, the other end of the capacitor C12 is connected to the output terminal B, one end of the resistor R11 is connected to the output terminal A, the other end of the resistor R11 is connected to the resistor R23, the other end of the resistor R23 is connected to the output terminal B, a connection point X1 between the capacitor C16 and the capacitor C17 is short-circuited with a connection point X2 between the capacitor C7 and the capacitor C12, a connection point X3 between the resistor R11 and the resistor R23 is short-circuited with the connection point X2, one end of the resistor R17 is connected to the connection point X3, and the other end of the resistor R17 is connected to the ground terminal.

4. The anti-interference circuit of a vibrating wire sensor according to claim 3, characterized in that: The suppression circuit (12) comprises a resistor R8, a resistor R24, a capacitor C5, a capacitor C14 and a common-mode inductor L1. The output end of the interference suppression circuit (1) comprises an output end W1 and an output end W2. Pin 1 of the common-mode inductor L1 is connected to the output end A, and pin 2 of the common-mode inductor L2 is connected to the output end B. One end of the resistor R8 is connected to the ground end, and the other end of the resistor R8 is connected to pin 4 of the common-mode inductor L1. The capacitor C5 is connected in parallel with the resistor R8. One end of the resistor R24 ​​is connected to the ground end, and the other end of the resistor R24 ​​is connected to pin 3 of the common-mode inductor L1. The capacitor C14 is connected in parallel with the resistor R24. Pin 4 of the common-mode inductor L1 is connected to the output end W1, and pin 3 of the common-mode inductor L1 is connected to the output end W2.

5. The anti-interference circuit of a vibrating wire sensor according to claim 1, characterized in that: The differential amplifier circuit (2) comprises a resistor R14, a resistor R3, a resistor R20, a resistor R25, a capacitor C4, a capacitor C10 and an operational amplifier U2, wherein one end of the resistor R14 is used to connect to the input end of the differential amplifier circuit (2), the other end of the resistor R14 is connected to the non-inverting input end of the operational amplifier U2, one end of the resistor R3 is connected to the ground end, the other end of the resistor R3 is connected to the non-inverting input end of the operational amplifier U2, the positive terminal of the operational amplifier U2 is connected to the power supply end AVCC, one end of the capacitor C4 is connected to the power supply end AVCC, and the other end of the capacitor C4 is connected to the ground end. The first embodiment of the present invention is connected to the ground terminal, one end of the resistor R20 is used to connect the input end of the differential amplifier circuit (2), the other end of the resistor R20 is connected to the inverting input end of the operational amplifier U2, the negative terminal of the operational amplifier U2 is connected to the power supply end AVCC-, one end of the capacitor C10 is connected to the ground terminal, the other end of the capacitor C10 is connected to the power supply end AVCC-, one end of the resistor R25 is connected to the inverting input end of the operational amplifier U2, the other end of the resistor R25 is connected to the output end of the operational amplifier U2, and the output end of the operational amplifier U2 is used to connect the output end of the differential amplifier circuit (2).

6. The anti-interference circuit of a vibrating wire sensor according to claim 1, characterized in that: The clamp circuit (3) comprises a resistor R12, a resistor R18, a resistor R5, a resistor R22, a capacitor C15, a transistor Q1, a transistor Q3 and an operational amplifier U1, one end of the resistor R12 is used to connect to the input end of the clamp circuit (3), the other end of the resistor R12 is connected to the inverting input end of the operational amplifier U1, one end of the resistor R18 is used to connect to the input end of the clamp circuit (3), the other end of the resistor R18 is connected to the non-inverting input end of the operational amplifier U1, one end of the resistor R22 is connected to the capacitor C15, the other end of the resistor R22 is connected to the non-inverting input end of the operational amplifier U1, and the capacitor C15 is connected to the inverting input end of the operational amplifier U1. The other end of is connected to the ground end, one end of the resistor R5 is connected to the inverting input end of the operational amplifier U1, the other end of the resistor R5 is connected to the output end of the operational amplifier U1, the base of the transistor Q3 is connected to the inverting input end of the operational amplifier U1, the collector and the base of the transistor Q3 are short-circuited, the emitter of the transistor Q3 is connected to the output end of the operational amplifier U1, the emitter of the transistor Q1 is connected to the inverting input end of the operational amplifier U1, the collector of the transistor Q1 is connected to the output end of the operational amplifier U1, the base and the collector of the transistor Q1 are short-circuited, and the output end of the operational amplifier U1 is used to connect the output end of the clamping circuit (3).

7. The anti-interference circuit of a vibrating wire sensor according to claim 1, characterized in that: The low-pass filter circuit (4) comprises a resistor R1, a resistor R9, a resistor R10, a resistor R15, a resistor R21, a capacitor C1, a capacitor C3, a capacitor C6, a capacitor C9, a capacitor C13 and an operational amplifier U3, one end of the resistor R15 is used to connect to the input end of the low-pass filter circuit (4), the other end of the resistor R15 is connected to the non-inverting input end of the operational amplifier U3, one end of the resistor R9 is used to connect to the input end of the low-pass filter circuit (4), the other end of the resistor R9 is connected to the resistor R10, the other end of the resistor R10 is connected to the inverting input end of the operational amplifier U3, one end of the capacitor C6 is connected to the connection point between the resistor R9 and the resistor R10, the other end of the capacitor C6 is connected to the ground end, one end of the resistor R1 is also connected to the connection point between the resistor R9 and the resistor R10, and the The other end of the resistor R1 is connected to the output end of the operational amplifier U3, one end of the capacitor C1 is connected to the inverting input end of the operational amplifier U3, the other end of the capacitor C1 is connected to the output end of the operational amplifier U3, one end of the resistor R21 is connected to the non-inverting input end of the operational amplifier U3, the other end of the resistor R21 is connected to the capacitor C13, the other end of the capacitor C13 is connected to the ground end, the positive end of the operational amplifier U3 is connected to the power supply end AVCC, one end of the capacitor C9 is connected to the power supply end AVCC, the other end of the capacitor C9 is connected to the ground end, the negative end of the operational amplifier U3 is connected to the power supply end AVCC-, one end of the capacitor C3 is connected to the power supply end AVCC-, the other end of the capacitor C3 is connected to the ground end, and the output end of the operational amplifier U3 is used to connect the output end of the low-pass filter circuit (4).

8. The anti-interference circuit of a vibrating-wire sensor according to claim 1, characterized in that: The zero-crossing detection circuit (5) comprises a resistor R2, a resistor R7, a resistor R6, a resistor R4, a resistor R13, a resistor R19, a capacitor C2, a capacitor C8, a capacitor C9, a capacitor C11, a MOS tube Q2 and a comparator U4, one end of the resistor R7 is used to connect to the input end of the zero-crossing detection circuit (5), the other end of the resistor R7 is connected to the non-inverting input end of the comparator U4, one end of the resistor R13 is used to connect to the input end of the zero-crossing detection circuit (5), the other end of the resistor R13 is connected to the reverse input end of the comparator U4, one end of the resistor R19 is connected to the reverse input end of the comparator U4, the other end of the resistor R19 is connected to the capacitor C11, the other end of the capacitor C11 is connected to the ground end, one end of the resistor R2 is connected to the non-inverting input end of the comparator U4, the other end of the resistor R2 is connected to the output end of the comparator U4, and the comparator The positive terminal of the comparator U4 is connected to the power supply terminal AVCC, one end of the capacitor C2 is connected to the power supply terminal AVCC, and the other end of the capacitor C2 is connected to the ground terminal. The negative terminal of the comparator U4 is connected to the power supply terminal AVCC-, one end of the capacitor C8 is connected to the power supply section AVCC-, and the other end of the capacitor C8 is connected to the ground terminal. One end of the resistor R6 is connected to the output end of the comparator U4, and the other end of the resistor R6 is connected to the power supply terminal AVCC. One end of the capacitor C9 is connected to the output end of the comparator U4, and the other end of the capacitor C9 is connected to the ground terminal. The gate of the MOS tube Q2 is connected to the output end of the comparator U4, the source of the MOS tube Q2 is connected to the ground terminal, the drain of the MOS tube Q2 is connected to the resistor R4, and the other end of the resistor R4 is connected to the power supply terminal DVCC. The drain of the MOS tube Q2 is also used to connect the output end of the zero-crossing detection circuit (5).

9. A vibrating wire sensor anti-interference device, characterized in that: The invention comprises an anti-interference circuit for a vibrating-wire sensor as claimed in any one of claims 1 to 8.

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