A vibrating wire sensor anti-interference circuit and device

Abstract

The application relates to the technical field of sensor signal processing, in particular to a vibrating string sensor anti-interference circuit and device, which comprises an interference suppression circuit, a differential amplification circuit, a clamping circuit, a low-pass filter circuit, a zero-crossing detection circuit and a processing module; an input end of the interference suppression circuit is used for connecting a vibrating string sensor; an output end of the interference suppression circuit is connected to an input end of the differential amplification circuit; an output end of the differential amplification circuit is connected to an input end of the clamping circuit; an output end of the clamping circuit is connected to an input end of the low-pass filter circuit; an output end of the low-pass filter circuit is connected to an input end of the zero-crossing detection circuit; and an output end of the zero-crossing detection circuit is connected to the processing module. The application has the effect of removing interference signals to obtain accurate to-be-measured signals.

Description

TECHNICAL FIELD

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

[0002] With the development of electronic technology, various sensors are designed, and vibrating string sensors as one of the sensors are applied in hydropower stations for detecting dams.

[0003] In actual use, the to-be-measured signal detected and output by the vibrating string sensor may jump, that is, the to-be-measured signal is mixed with an interference signal, so that the final obtained signal is inaccurate, thereby resulting in inaccurate detection results. Therefore, how to process the signal to obtain an accurate to-be-measured signal becomes a problem to be solved. SUMMARY

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

[0005] In a first aspect, the vibrating string sensor anti-interference circuit provided by the present application adopts the following technical scheme:

[0006] The vibrating string sensor anti-interference circuit comprises an interference suppression circuit, a differential amplification circuit, a clamping circuit, a low-pass filter circuit, a zero-crossing detection circuit and a processing module; an input end of the interference suppression circuit is used for connecting a vibrating string sensor, an output end of the interference suppression circuit is connected to an input end of the differential amplification circuit, an output end of the differential amplification circuit is connected to an input end of the clamping circuit, an output end of the clamping circuit is connected to an input end of the low-pass filter circuit, an output end of the low-pass filter circuit is connected to an input end of the zero-crossing detection circuit, and an output end of the zero-crossing detection circuit is connected to the processing module.

[0007] By adopting the technical scheme, the interference suppression circuit receives the to-be-tested signal transmitted by the vibrating string sensor, can protect the subsequent circuit when encountering a surge current generated by a lightning stroke, can avoid the influence of different vibrating string sensor connection cable lengths, different input capacitor capacitances and line imbalance on the working characteristics of the circuit, can filter out high-frequency noise, attenuate common-mode signal amplitude, and can also prevent signal tailing; the differential amplification 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 saturation of the subsequent circuit; the low-pass filter circuit is used to extract a low-frequency signal, attenuate a high-frequency signal, and adjust the to-be-tested signal to a suitable detection amplitude; and the zero-crossing detection circuit is used to convert the to-be-tested signal of a bipolar sine wave into a unipolar square wave signal that can be recognized by the processing module. The interference signal in the to-be-tested signal is filtered out, so that a more accurate to-be-tested signal is obtained, and the detection result is more accurate.

[0008] Optionally, the interference suppression circuit comprises a first filter circuit and a suppression circuit, the first filter circuit is connected to an input end of the interference suppression circuit, the first filter circuit is further connected to the suppression circuit, and the suppression circuit is further connected to an output end of the interference suppression circuit.

[0009] Optionally, the first filter circuit 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 end A and an output end B, the input end of the interference suppression circuit comprises an input end V1 and an input end V2, the input end V1 is connected to the resistor R16, the other end of the resistor R16 is connected to the output end A, the input end V2 is connected to the resistor R26, the other end of the resistor R26 is connected to the output end B, one end of the capacitor C16 is connected to the input end 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 input end V2, one end of the capacitor C7 is connected to the output end 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 end B, one end of the resistor R11 is connected to the output end 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 end B, the connection point X1 of the capacitor C16 and the capacitor C17 is short-circuited with the connection point X2 of the capacitor C7 and the capacitor C12, the connection point X3 of 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 a ground end.

[0010] By adopting the technical scheme, the components in the first filter circuit form a pi-type filter circuit, which can solve the influence of different lengths of the connecting cable of the vibrating string sensor, different capacitances of the input capacitor and line imbalance on the working characteristics of the circuit, that is, the interference signal in the to-be-measured signal can be reduced; by arranging the resistor R17, the ground current can be limited when the vibrating string sensor encounters a lightning surge current, thereby protecting the subsequent circuit.

[0011] Optionally, the suppression circuit includes a resistor R8, a resistor R24, a capacitor C5, a capacitor C14 and a common-mode inductor L1, an output end of the interference suppression circuit includes an output end W1 and an output end W2, a 1 pin of the common-mode inductor L1 is connected to the output end A, a 2 pin of the common-mode inductor L2 is connected to the output end B, one end of the resistor R8 is connected to a ground end, the other end of the resistor R8 is connected to a 4 pin 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 a 3 pin of the common-mode inductor L1, the capacitor C14 is connected in parallel with the resistor R24, the 4 pin of the common-mode inductor L1 is connected to the output end W1, and the 3 pin of the common-mode inductor L1 is connected to the output end W2.

[0012] By adopting the technical scheme, the suppression circuit composed of the common-mode inductor L1 and the capacitor and the resistor can filter out high-frequency noise, attenuate the amplitude of the common-mode signal, and prevent the amplitude of the common-mode signal from being too large and prevent the generation of signal tailing.

[0013] Optionally, the differential amplification circuit comprises resistor R14, resistor R3, resistor R20, resistor R25, capacitor C4, capacitor C10 and operational amplifier U2, one end of the resistor R14 is used for connecting the input end of the differential amplification 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 with 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 ground end, one end of the resistor R20 is used for connecting the input end of the differential amplification circuit, 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 with the power supply end AVCC-, one end of the capacitor C10 is connected to the ground end, 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 for connecting the output end of the differential amplification circuit.

[0014] Optionally, the clamping circuit comprises resistor R12, resistor R18, resistor R5, resistor R22, capacitor C15, transistor Q1, transistor Q3 and operational amplifier U1, one end of the resistor R12 is used for connecting 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 for connecting 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, the other end of the capacitor C15 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 for connecting the output end of the clamping circuit.

[0015] By adopting the technical scheme, the resistor R12 can provide a large bias working current for the triode, the resistor R18 can match the impedances of the two input ends of the operational amplifier U1, meanwhile, the resistor R18, the resistor R22 and the capacitor form a low-pass filter to extract low-frequency signals and attenuate high-frequency signals; the resistor R22 improves the phase of the low-frequency signals and reduces the signal delay. The clamping circuit can clamp high-frequency signals with large amplitude to prevent saturation of the subsequent circuit.

[0016] Optionally, the low-pass filter circuit 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 for connecting an input end of the low-pass filter circuit, the other end of the resistor R15 is connected to an inverting input end of the operational amplifier U3, one end of the resistor R9 is used for connecting 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 a non-inverting input end of the operational amplifier U3, one end of the capacitor C6 is connected to a connection point of the resistor R9 and the resistor R10, the other end of the capacitor C6 is connected to a ground end, one end of the resistor R1 is also connected to the connection point of the resistor R9 and the resistor R10, the other end of the resistor R1 is connected to an 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, a positive electrode end of the operational amplifier U3 is connected to a power supply end AVCC, one end of the capacitor C3 is connected to the power supply end AVCC, a negative electrode end of the operational amplifier U3 is connected to a 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 for connecting an output end of the low-pass filter circuit.

[0017] Optionally, the zero-crossing detection circuit comprises resistor R2, resistor R7, resistor R6, resistor R4, resistor R13, resistor R19, capacitor C2, capacitor C8, capacitor C9, capacitor C11, MOS tube Q2 and comparator U4, one end of the resistor R7 is used for connecting 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 for connecting the input end of the zero-crossing detection circuit, the other end of the resistor R13 is connected to the inverting 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, the positive end of the comparator U4 is connected with 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 with the power supply end AVCC-, one end of the capacitor C8 is connected to the power supply end 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 with the power supply end DVCC, and the drain of the MOS tube Q2 is also used for connecting the output end of the zero-crossing detection circuit.

[0018] By adopting the above technical scheme, the resistor R7 and the resistor R2 are used for setting the hysteresis of the comparator U4, so as to eliminate the case that 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, so as to eliminate the sharp pulse generated in the instant 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 which can be recognized by the processing module.

[0019] In the second aspect, the anti-interference device for the vibrating string sensor adopts the technical scheme as follows:

[0020] The anti-interference device for the vibrating string sensor comprises the anti-interference circuit for the vibrating string sensor as described in the first aspect.

[0021] To sum up, the present application includes at least one of the following beneficial technical effects:

[0022] 1. The interference suppression circuit receives the to-be-tested signal transmitted by the vibrating string sensor, can protect the subsequent circuit when encountering a surge current generated by a lightning strike, can avoid the influence of different lengths of vibrating string sensor connection cables, different input capacitances, and line imbalance on the working characteristics of the circuit, can filter out high-frequency noise and attenuate the common-mode signal amplitude, and can also prevent signal tailing; the differential amplification circuit is used to amplify the differential-mode signal and avoid the attenuation of the common-mode signal into a differential-mode signal; the clamping circuit is used to clamp the high-frequency signal with a large amplitude to prevent the saturation of the subsequent circuit; the low-pass filter circuit is used to extract low-frequency signals, attenuate high-frequency signals, and adjust the to-be-tested signal to an appropriate detection amplitude; and the zero-crossing detection circuit is used to convert the to-be-tested signal of a bipolar sine wave into a unipolar square wave signal that can be recognized by the processing module. The interference signal in the to-be-tested signal is filtered out, thereby obtaining a more accurate to-be-tested signal and a more accurate detection result.

[0023] 2. The components in the first filter circuit form a π-type filter circuit, which can solve the influence of different lengths of vibrating string sensor connection cables, different input capacitances, and line imbalance on the working characteristics of the circuit, i.e., can reduce the interference signal in the to-be-tested signal; by setting the resistor R17, the ground current can be limited when the vibrating string sensor encounters a surge current generated by a lightning strike, thereby protecting the subsequent circuit. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a connection block diagram showing the whole of the embodiment.

[0025] Figure 2 is a circuit principle diagram showing the interference suppression circuit of the embodiment.

[0026] Figure 3 is a circuit principle diagram showing the differential amplification circuit of the embodiment.

[0027] Figure 4 is a circuit principle diagram showing the clamping circuit of the embodiment.

[0028] Figure 5 is a circuit principle diagram showing the low-pass filter circuit of the embodiment.

[0029] Figure 6 is a circuit principle diagram showing the zero-crossing detection circuit of the embodiment.

[0030] BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0031] The application will be further described below in conjunction with the accompanying drawings. Figures 1-6 The application will be further described below in conjunction with the accompanying drawings.

[0032] The application discloses a vibrating string sensor anti-interference circuit. Referring to Figure 1 The vibrating string sensor anti-interference circuit comprises an interference suppression circuit 1, a differential amplification circuit 2, a clamping 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 for connecting the vibrating string sensor, the output end of the interference suppression circuit 1 is connected to the input end of the differential amplification circuit 2, the output end of the differential amplification circuit 2 is connected to the input end of the clamping circuit 3, the output end of the clamping 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.

[0033] Referring to Figure 2 The interference suppression circuit 1 comprises a first filter circuit 11 and a suppression circuit 12. The first filter circuit 11 is connected to the input end of the interference suppression circuit 1 and 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.

[0034] Specifically, the first filter 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 end A and an output end B. The input end of the interference suppression circuit 1 comprises an input end V1 and an input end V2. The input end V1 is connected to the resistor R16, and the other end of the resistor R16 is connected to the output end A. The input end V2 is connected to the resistor R26, and the other end of the resistor R26 is connected to the output end B. One end of the capacitor C16 is connected to the input end 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 end V2. One end of the capacitor C7 is connected to the output end A, and 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 end B. One end of the resistor R11 is connected to the output end A, and 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 end B. The connection point X1 of the capacitor C16 and the capacitor C17 is short-circuited with the connection point X2 of the capacitor C7 and the capacitor C12. The connection point X3 of 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 end.

[0035] The components of the first filter circuit 11 form a π-type filter circuit, which is used to solve the influence of different lengths of the connecting cable of the external vibrating string sensor, different input capacitances and line imbalance on the operation of the circuit, i.e. to improve the accuracy of the signal. Moreover, by setting the resistor R17, the size of the ground current can be limited when the vibrating string sensor encounters a surge current caused by lightning, thereby achieving the effect of protecting the subsequent circuit.

[0036] The interference 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, the 1 pin of the common mode inductor L1 is connected to the output end A, the 2 pin 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 the 4 pin 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 the 3 pin of the common mode inductor L1, the capacitor C14 is connected in parallel with the resistor R24, the 4 pin of the common mode inductor L1 is connected to the output end W1, and the 3 pin of the common mode inductor L1 is connected to the output end W2.

[0037] The common mode inductor L1, the resistor and the capacitor form the interference suppression circuit 12, which is used to filter high-frequency noise in the circuit, can attenuate the amplitude of the common mode signal, reduce the possibility that the amplitude of the common mode signal exceeds the maximum common mode voltage allowed by the subsequent circuit, and can also avoid the phenomenon of signal tailing.

[0038] With reference to Figure 3 The differential amplification 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 amplification circuit 2, i.e. 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 end 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 ground end, one end of the resistor R20 is used to connect the input end of the differential amplification circuit 2, i.e. connected to the output end W2, the other end of the resistor R20 is connected to the inverting input end of the operational amplifier U2, the negative terminal end of the operational amplifier U2 is connected to the power supply end AVCC-, one end of the capacitor C10 is connected to the ground end, 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 amplification circuit 2.

[0039] The differential amplification circuit 2 can suppress the attenuated common mode signal and amplify the differential mode signal. The operational amplifier U2 can avoid the interference narrow pulse from being broadened, thereby improving the possibility of the subsequent circuit to filter out the interference narrow pulse. The differential amplification circuit 2 can also avoid the attenuated common mode signal from being converted into the differential mode signal. The resistor in the differential amplification circuit 2 is not less than the resistor with the precision of one thousandth.

[0040] With reference to Figure 4 The clamping circuit 3 comprises the resistor R12, the resistor R18, the resistor R5, the resistor R22, the capacitor C15, the transistor Q1, the transistor Q3 and the operational amplifier U1. One end of the resistor R12 is used to connect the input end of the clamping circuit 3, i.e. 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 clamping circuit 3, i.e. 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. The other end of the resistor R22 is connected to the non-inverting input end of the operational amplifier U1. The other end of the capacitor C15 is connected to the ground. 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 shorted. 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 shorted. The output end of the operational amplifier U1 is used to connect the output end of the clamping circuit 3.

[0041] The transistors Q1 and Q3 are both PNP type and made of germanium.

[0042] In the inverting input terminal of the operational amplifier U1 in series resistor R12, the transistor can provide a larger bias current, so as to improve the speed of the transistor on-off; in the non-inverting input terminal of the operational amplifier U1 in series resistor R18, the input impedance of the operational amplifier U1 can be matched, so that the operational amplifier U1 works in a more ideal condition. At the same time, resistor R18, resistor R22 and capacitor C15 constitute a low-pass filter, which can extract low-frequency signals and attenuate high-frequency signals. The signal difference between the non-inverting input terminal signal and the inverting input terminal signal of the operational amplifier U1 can eliminate the influence of low-frequency signals on the measured signal. Resistor R22 can improve the phase of low-frequency signals and reduce signal delay. When the measured signal is at a high frequency of 5000 Hz, the delay will not affect the measurement of the signal. The signal difference between the non-inverting input terminal signal and the inverting input terminal signal of the operational amplifier U1 is amplified and then clamped by the transistor to the high-frequency signal with a larger amplitude, preventing the operational amplifier in the subsequent circuit from being saturated.

[0043] Wherein, the signal to be measured is the signal detected by the vibrating string sensor, that is, the required signal.

[0044] Referring to Figure 5The low-pass filter circuit 4 comprises resistor R1, resistor R9, resistor R10, resistor R15, resistor R21, capacitor C1, capacitor C3, capacitor C6, capacitor C9, capacitor C13 and operational amplifier U3. One end of resistor R15 is connected to the input of the low-pass filter circuit 4, i.e. to the output of operational amplifier U1. The other end of resistor R15 is connected to the non-inverting input of operational amplifier U3. One end of resistor R9 is connected to the input of the low-pass filter circuit 4, i.e. to the output of operational amplifier U1. The other end of resistor R9 is connected to resistor R10. The other end of resistor R10 is connected to the inverting input of operational amplifier U3. One end of capacitor C6 is connected to the connection point of resistor R9 and resistor R10. The other end of capacitor C6 is connected to the ground. One end of resistor R1 is also connected to the connection point of resistor R9 and resistor R10. The other end of resistor R1 is connected to the output of operational amplifier U3. One end of capacitor C1 is connected to the inverting input of operational amplifier U3. The other end of capacitor C1 is connected to the output of operational amplifier U3. One end of resistor R21 is connected to the non-inverting input 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. The positive terminal of operational amplifier U3 is connected to the power supply terminal AVCC. One end of capacitor C9 is connected to the power supply terminal AVCC. The other end of capacitor C9 is connected to the ground. The negative terminal of operational amplifier U3 is connected to the power supply terminal AVCC-. One end of capacitor C3 is connected to the power supply terminal AVCC-. The other end of capacitor C3 is connected to the ground. The output of operational amplifier U3 is connected to the output of the low-pass filter circuit 4.

[0045] Resistor R15, resistor R21 and capacitor C13 constitute a low-pass filter, which extracts low-frequency signals and attenuates high-frequency signals. Resistor R21 can improve the phase of low-frequency signals and reduce signal delay. When the to-be-measured signal is at a high frequency of 5000 Hz, the delay will not affect the signal measurement. Resistor R10 is correspondingly arranged to achieve impedance matching at the input of operational amplifier U3. The signal difference between the non-inverting input signal and the inverting input signal of operational amplifier U3 is adjusted to an appropriate amplitude for detection through a multi-stage feedback low-pass filter.

[0046] In the figure, the power supply terminal of operational amplifier U1 is not connected to the power supply because operational amplifier U1 and operational amplifier U3 are both integrated, i.e. two operational amplifiers are included in the same IC package module, and operational amplifier U1 is also powered when operational amplifier U3 is powered.

[0047] Reference Figure 6The zero-crossing detection circuit 5 comprises resistor R2, resistor R7, resistor R6, resistor R4, resistor R13, resistor R19, capacitor C2, capacitor C8, capacitor C9, capacitor C11, MOS tube Q2 and comparator U4, one end of the resistor R7 is used for connecting the input end of the zero-crossing detection circuit 5, i.e. 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 for connecting the input end of the zero-crossing detection circuit 5, i.e. connected to the output end of the operational amplifier U3, the other end of the resistor R13 is connected to the inverting 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, the positive end of the comparator U4 is connected with 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 with the power supply end AVCC-, one end of the capacitor C8 is connected to the power supply end 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 with the power supply end DVCC, and the drain of the MOS tube Q2 is also used for connecting the output end of the zero-crossing detection circuit 5, i.e. connected to the processing module 6.

[0048] wherein, Figure 6 The gate and the source of the MOS tube Q2 are short-circuited with a transient suppression diode, the transient suppression diode belongs to the MOS tube Q2, i.e. the transient suppression diode is integrated in the MOS tube Q2.

[0049] The resistor R13, the resistor R19 and the capacitor C11 in the zero-crossing detection circuit 5 constitute a low-pass filter for attenuating high-frequency signals in the to-be-detected signal and taking the low-frequency signals in the to-be-detected signal as a comparator reference signal which changes in real time following the low-frequency signals in the to-be-detected signal. The resistor R7 and the resistor R2 are used to set the hysteresis of the comparator U4 to eliminate abnormal flip signals of the comparator U4 caused by 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 in the opening moment of the MOS tube Q2, so as to realize conversion of the to-be-detected signal of the bipolar sine wave into a unipolar square wave signal. The transient suppression diode in the MOS tube Q2 is used to avoid breakdown of components caused by static electricity, thereby playing a protection role.

[0050] The converted square wave signal, i.e., the to-be-detected signal, is transmitted to the processing module 6. The processing module 6 receives all signals, sorts the received signals based on the pulse period from small to large, then calculates the first average value of the middle period of the to-be-detected signal, sets the threshold value as ten percent to twenty percent of the first average value, filters out all periods exceeding the threshold value, and then calculates the second average value of the remaining periods of the to-be-detected signal, i.e., obtains the high-precision measurement value of the to-be-detected signal.

[0051] Based on the above circuit, the high-pass filtering effect is realized through three-stage low-pass filtering subtraction operation, and the 50Hz interference signal can be attenuated by 40db.

[0052] Through the circuit combination of the embodiment, the interference signal in the to-be-detected signal can be filtered to a greater extent, new interference signals can be reduced, and the to-be-detected signal is more consistent with the detection range. Finally, a more accurate detection result can be obtained.

[0053] The embodiment of the application further discloses a vibrating string sensor anti-interference device, and the vibrating string sensor anti-interference device comprises the vibrating string sensor anti-interference circuit.

[0054] The above are preferred embodiments of the application, and do not limit the protection scope of the application, so that: equivalent changes made according to the structure, shape, principle of the application should be covered in the protection scope of the application.

Claims

1. A vibrating wire sensor anti-interference circuit, characterized in that: The interference suppression circuit (1), the differential amplifier circuit (2), the clamping circuit (3), the low-pass filter circuit (4), the zero-crossing detection circuit (5) and the processing module (6); the input end of the interference suppression circuit (1) is used for connecting 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 clamping circuit (3), the output end of the clamping 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), the output end of the zero-crossing detection circuit (5) is connected to the processing module (6); the interference suppression circuit (1) comprises a first filter circuit (11) and a suppression circuit (12), the first filter circuit (11) is connected to the input end of the interference suppression circuit (1), the first filter circuit (11) is also connected to the suppression circuit (12), and the suppression circuit (12) is also connected to the output end of the interference suppression circuit (1); the first filter 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 end A and an output end B, the input end of the interference suppression circuit (1) comprises an input end V1 and an input end V2, the input end V1 is connected to the resistor R16, the other end of the resistor R16 is connected to the output end A, the input end V2 is connected to the resistor R26, the other end of the resistor R26 is connected to the output end B, one end of the capacitor C16 is connected to the input end 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 input end V2, one end of the capacitor C7 is connected to the output end 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 end B, one end of the resistor R11 is connected to the output end 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 end B, the connection point X1 of the capacitor C16 and the capacitor C17 is short-circuited with the connection point X2 of the capacitor C7 and the capacitor C12, the connection point X3 of 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, the other end of the resistor R17 is connected to the ground end, and the resistor R17 is used for limiting the ground current when the vibrating string sensor encounters lightning surge current, so as to protect the circuit; wherein each component in the first filter circuit forms a π-type filter circuit.The clamping circuit (3) comprises resistor R12, resistor R18, resistor R5, resistor R22, capacitor C15, triode Q1, triode Q3 and operational amplifier U1, one end of the resistor R12 is used for connecting the input end of the clamping 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 for connecting the input end of the clamping 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, the other end of the capacitor C15 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 triode Q3 is connected to the inverting input end of the operational amplifier U1, the collector and the base of the triode Q3 are short-circuited, the emitter of the triode Q3 is connected to the output end of the operational amplifier U1, the emitter of the triode Q1 is connected to the inverting input end of the operational amplifier U1, the collector of the triode Q1 is connected to the output end of the operational amplifier U1, the base and the collector of the triode Q1 are short-circuited, and the output end of the operational amplifier U1 is used for connecting the output end of the clamping circuit (3).The low-pass filter circuit (4) comprises resistor R1, resistor R9, resistor R10, resistor R15, resistor R21, capacitor C1, capacitor C3, capacitor C6, capacitor C9, capacitor C13 and operational amplifier U3, one end of the resistor R15 is used for connecting 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 for connecting 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 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 connection point of the resistor R9 and the resistor R10, 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 terminal of the operational amplifier U3 is connected with 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 terminal of the operational amplifier U3 is connected with 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 for connecting the output end of the low-pass filter circuit (4).The zero-crossing detection circuit (5) comprises resistor R2, resistor R7, resistor R6, resistor R4, resistor R13, resistor R19, capacitor C2, capacitor C8, capacitor C9, capacitor C11, MOS tube Q2 and comparator U4, one end of the resistor R7 is used for connecting 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 for connecting the input end of the zero-crossing detection circuit (5), the other end of the resistor R13 is connected to the inverting 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, the positive electrode end of the comparator U4 is connected with 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 electrode end of the comparator U4 is connected with the power supply end AVCC-, one end of the capacitor C8 is connected to the power supply end 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 with the power supply end DVCC, and the drain of the MOS tube Q2 is also used for connecting the output end of the zero-crossing detection circuit (5); the resistor R13, the resistor R19 and the capacitor C11 in the zero-crossing detection circuit constitute a low-pass filter, which is used for attenuating high-frequency signals in the to-be-detected signal and taking the high-frequency signals as a comparator reference signal, wherein the comparator reference signal changes in real time following the low-frequency signals of the to-be-detected signal; the resistor R7 and the resistor R2 are used for setting the hysteresis of the comparator U4, so as to eliminate abnormal flip signals of the comparator U4 caused by the jitter of the comparison signal; the capacitor C9 is used for increasing the junction capacitance between the gate and the source of the MOS tube Q2, so as to eliminate the spike pulse generated in the instant when the MOS tube Q2 is turned on, realize the conversion of the to-be-detected signal of the bipolar sine wave into a unipolar square wave signal, take the square wave signal as the to-be-detected signal, and transmit the square wave signal to the processing module (6), and the transient suppression diode in the MOS tube Q2 is used for avoiding the breakdown of the components caused by static electricity.The processing module (6) receives all signals, sorts the received signals from small to large based on pulse period, calculates the first average value of the middle period of the to-be-measured signal, sets the threshold value to 10% to 20% of the first average value, filters out all periods exceeding the threshold value, and calculates the second average value of the remaining to-be-measured signal periods, that is, the high-precision measurement value of the to-be-measured signal.

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

3. The anti-interference circuit of a vibrating wire sensor according to claim 1, characterized in that: The differential amplification circuit (2) includes resistor R14, resistor R3, resistor R20, resistor R25, capacitor C4, capacitor C10 and operational amplifier U2, one end of the resistor R14 is used for connecting the input end of the differential amplification 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 electrode end of the operational amplifier U2 is connected with 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 ground end, one end of the resistor R20 is used for connecting the input end of the differential amplification circuit (2), the other end of the resistor R20 is connected to the inverting input end of the operational amplifier U2, the negative electrode end of the operational amplifier U2 is connected with the power supply end AVCC-, one end of the capacitor C10 is connected to the ground end, 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 for connecting the output end of the differential amplification circuit (2).

4. An anti-interference device for a vibrating wire sensor, characterized in that: The vibration sensor anti-interference circuit comprises a vibration sensor anti-interference circuit as claimed in any one of claims 1 to 3.

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