Pulse width detection circuit and inductive displacement sensor

Abstract

The application discloses a pulse width detection circuit and an inductive displacement sensor, and comprises an oscillation circuit, a coil resonance circuit and a modulation circuit; the output end of the oscillation circuit is connected with the input end of the coil resonance circuit, and the output end of the coil resonance circuit is connected with the modulation circuit; the oscillation circuit is used for generating a driving square wave signal and outputting the driving square wave signal to the coil resonance circuit; the coil resonance circuit is used for generating a sine wave signal with the same frequency as the driving square wave signal and outputting the sine wave signal to the modulation circuit; and the modulation circuit is used for converting the sine wave signal into a pulse width modulation signal with a pulse width being proportional to a measured displacement. The application converts the amplitude variation of a probe sine wave into a pulse width modulation wave to improve the signal-to-noise ratio and the anti-interference capability of the inductive displacement sensor detection, and only an RC integral smoothing circuit and a normalization circuit are needed to regulate the required signal of a user.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of manufacturing of inductive displacement sensors, in particular to a pulse width detection circuit and an inductive displacement sensor. BACKGROUND

[0002] The existing inductive displacement sensors on the market adopt two detection methods of diode envelope detection and synchronous lock-in amplifier synchronous detection, both of which are amplitude detection methods, and the signal-to-noise ratio is not very high, and it is difficult to achieve 0.1um resolution.

[0003] The diode envelope detection method has poor anti-electromagnetic interference ability, small sensitivity, and needs subsequent conditioning circuit to amplify the weak detected signal, and the signal-to-noise ratio is relatively low.

[0004] The synchronous lock-in amplifier synchronous detection method can detect the signal with the same frequency as the working frequency of the probe in the weak signal, and discard other noise signals, and the anti-interference ability is obviously stronger than that of the diode envelope detection method, but since the detected signal is relatively weak, it needs to rely on subsequent circuit for high-gain amplification, and in the amplification process, it is difficult to avoid amplifying noise signals together, thereby reducing the signal-to-noise ratio.

[0005] Therefore, the low signal-to-noise ratio and poor anti-interference ability of the existing inductive displacement sensor detection method have become a technical problem to be solved by those skilled in the art. SUMMARY

[0006] The present application provides a pulse width detection circuit and an inductive displacement sensor, which solves the technical problem of low signal-to-noise ratio and poor anti-interference ability of the existing inductive displacement sensor detection method.

[0007] To solve the above technical problems, the technical solution provided by the present application is:

[0008] A pulse width detection circuit for an inductive displacement sensor, comprising an oscillation circuit, a coil resonance circuit and a modulation circuit; the output end of the oscillation circuit is connected with the input end of the coil resonance circuit, and the output end of the coil resonance circuit is connected with the modulation circuit;

[0009] The oscillation circuit is used for generating a driving square wave signal and outputting the driving square wave signal to the coil resonance circuit;

[0010] The coil resonance circuit is used for generating a sinusoidal signal with the same frequency as the driving square wave signal and outputting the sinusoidal signal to the modulation circuit;

[0011] The modulation circuit is used for converting the sinusoidal signal into a pulse width modulation signal with a pulse width proportional to the measured displacement.

[0012] Preferably, the oscillation circuit comprises a crystal oscillator CY1 and a quadrature phase shifter IC1; an output terminal of the crystal oscillator CY1 is connected with an input terminal of the quadrature phase shifter IC1; the quadrature phase shifter IC1 comprises a first output terminal and a second output terminal, the first output terminal is connected with an input terminal of the coil resonance circuit, and the second output terminal is connected with the modulation circuit;

[0013] The crystal oscillator CY1 is used to output a square wave pulse to the quadrature phase shifter IC1; the quadrature phase shifter IC1 is used to convert the square wave pulse into a first square wave signal and a second square wave signal which are in phase quadrature, and output the first square wave signal as a driving square wave signal to the coil resonance circuit and output the second square wave signal to the modulation circuit.

[0014] Preferably, the coil resonance circuit comprises a probe coil L1 and a resonance capacitor C1, the probe coil L1 and the resonance capacitor C1 constitute a parallel resonance circuit, a first terminal of the parallel resonance circuit is connected with the first output terminal of the quadrature phase shifter IC1 and a first input terminal of the modulation circuit respectively, and a second terminal of the parallel resonance circuit is grounded; the parallel resonance circuit is used to generate a sinusoidal signal with the same frequency as the driving square wave signal at two ends of the probe coil L1 and output the sinusoidal signal to the modulation circuit.

[0015] Preferably, the modulation circuit comprises an inverter IC2, an XOR gate IC3 and an isolation capacitor C2; a first terminal of the isolation capacitor C2 is connected with the first terminal of the parallel resonance circuit, a second terminal of the isolation capacitor is connected with an input terminal of the inverter IC2, an output terminal of the inverter IC2 is connected with a first input terminal of the XOR gate IC3, and a second input terminal of the XOR gate IC3 is connected with the second terminal of the quadrature phase shifter IC1.

[0016] The isolation capacitor is used to isolate a direct current component in the sinusoidal signal and output the isolated sinusoidal signal to the inverter IC2.

[0017] The inverter IC2 is used to perform inversion processing on the isolated sinusoidal signal and output the inversion-processed sinusoidal signal to the XOR gate IC3; the XOR gate IC3 is used to perform XOR processing on the inversion-processed sinusoidal signal and the second square wave signal to obtain a pulse width modulation signal whose pulse width is proportional to the measured displacement.

[0018] Preferably, the square wave pulse output by the crystal oscillator CY1 has a frequency of 300 KHz to 1 MHz, the first square wave signal output by the first output terminal of the quadrature phase shifter IC1 has a phase of 90 degrees, and the second square wave signal output by the second output terminal of the quadrature phase shifter IC1 has a phase of 0 degrees.

[0019] An inductive displacement sensor comprises:

[0020] The above-mentioned pulse width detection circuit and a signal conditioning circuit connected with the pulse width detection circuit.

[0021] The signal conditioning circuit is used for converting the pulse width modulation signal outputted by the pulse width detection circuit and proportional to the displacement into a voltage signal proportional to the displacement.

[0022] Preferably, the signal conditioning circuit comprises a smoothing filter circuit and a normalization circuit, the input end of the smoothing filter circuit is connected with the output end of the pulse width detection circuit, and the output end of the smoothing filter circuit is connected with the input end of the normalization circuit.

[0023] The smoothing filter circuit is used for smoothing filtering the pulse width modulation signal outputted by the pulse width detection circuit and proportional to the displacement, removing the pulsating component, and obtaining a direct current voltage value proportional to the displacement.

[0024] The normalization circuit is used for amplifying and shifting the direct current voltage value and normalizing it into a preset output mode.

[0025] Preferably, the smoothing filter circuit comprises an integral resistance R1 and an integral capacitance C3, the first end of the integral resistance R1 is connected with the output end of the pulse width detection circuit, the second end is connected with the first end of the integral capacitance C3, and the second end of the integral capacitance C3 is grounded.

[0026] Preferably, the normalization circuit comprises a gain resistance R2, a gain resistance R3 and a normalization conditioning circuit IC4, the first input end of the normalization conditioning circuit IC4 is connected with the first end of the integral capacitance C3, the second input end of the normalization conditioning circuit IC4 is respectively connected with the first end of the gain resistance R2 and the gain resistance R3, the second end of the gain resistance R2 is grounded, and the second end of the gain resistance R3 is connected with the output end of the normalization conditioning circuit IC4.

[0027] Preferably, the normalization conditioning circuit IC4 is an operational amplifier.

[0028] The present application has the following beneficial effects:

[0029] 1. The pulse width detection circuit and the inductive displacement sensor in the application, comprising an oscillation circuit, a coil resonance circuit and a modulation circuit; the output end of the oscillation circuit is connected with the input end of the coil resonance circuit, and the output end of the coil resonance circuit is connected with the modulation circuit; the oscillation circuit is used for generating a driving square wave signal and outputting the driving square wave signal to the coil resonance circuit; the coil resonance circuit is used for generating a sine wave signal with the same frequency as the driving square wave signal and outputting the sine wave signal to the modulation circuit; and the modulation circuit is used for converting the sine wave signal into a pulse width modulation signal with the pulse width being proportional to the measured displacement. Compared with the prior art, the application converts the amplitude change of the probe sine wave into a pulse width modulation wave for detection, so that the signal-to-noise ratio and the anti-interference capability of the inductive displacement sensor detection can be improved. Only an RC integral smoothing circuit and a normalization circuit are needed to process the signal required by the user.

[0030] In addition to the objects, features and advantages described above, the application has other objects, features and advantages. The application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the application, and the illustrative embodiments of the application and their description serve to explain the application. The accompanying drawings do not constitute an inappropriate limitation on the application. In the drawings:

[0032] Figure 1 is an inductive displacement sensor in the preferred embodiment of the application;

[0033] Figure 2 is a crystal oscillator waveform diagram in the preferred embodiment of the application;

[0034] Figure 3 is a quadrature square wave diagram in the preferred embodiment of the application;

[0035] Figure 4 is a probe coil resonance waveform diagram in the preferred embodiment of the application;

[0036] Figure 5 is a probe coil sine wave reverse operation waveform diagram in the preferred embodiment of the application;

[0037] Figure 6 is a pulse width modulation wave PWM1 waveform diagram after the sine wave reverse operation in the preferred embodiment of the application;

[0038] Figure 7 is a pulse width modulation wave PWM2 waveform diagram after the exclusive OR operation in the preferred embodiment of the application;

[0039] Figure 8 is an RC integral smoothing filtered waveform diagram in the preferred embodiment of the application;

[0040] Figure 9 is the waveform diagram of the probe coil sine wave after the XOR operation in the preferred embodiment of the present application with the amplitude of ±5V;

[0041] Figure 10 is the waveform diagram of the probe coil sine wave after the XOR operation in the preferred embodiment of the present application with the amplitude of ±5V;

[0042] Figure 11 is the waveform diagram of the probe coil sine wave after the XOR operation in the preferred embodiment of the present application with the amplitude of ±5V;

[0043] Figure 12 is the waveform diagram of the probe coil sine wave after the XOR operation in the preferred embodiment of the present application with the amplitude of ±5V;

[0044] Figure 13 is the pulse width comparison diagram after the XOR operation of the sine wave with the amplitude of ±5V and ±3V in the preferred embodiment of the present application;

[0045] Figure 14 is the pulse width comparison diagram after the XOR operation of the sine wave with the amplitude of ±5V and ±3V in the preferred embodiment of the present application;

[0046] Figure 15 is the simulation diagram of the sine wave with the peak amplitude of 5V in the preferred embodiment of the present application;

[0047] Figure 16 is the simulation diagram of the sine wave with the peak amplitude of 3V in the preferred embodiment of the present application;

[0048] Figure 17 is the simulation diagram of the sine wave with the peak amplitude of 2V in the preferred embodiment of the present application. DETAILED DESCRIPTION

[0049] The embodiments of the present application are described in detail below with reference to the accompanying drawings, but the present application can be implemented in various different ways as limited and covered by the claims.

[0050] Embodiment one:

[0051] In this embodiment, a pulse width detection circuit is disclosed, which is used in an inductive displacement sensor and includes an oscillation circuit, a coil resonance circuit and a modulation circuit; the output end of the oscillation circuit is connected with the input end of the coil resonance circuit, and the output end of the coil resonance circuit is connected with the modulation circuit;

[0052] The oscillation circuit is used to generate a driving square wave signal and output the driving square wave signal to the coil resonance circuit;

[0053] The coil resonance circuit is used to generate a sine wave signal with the same frequency as the driving square wave signal and output the sine wave signal to the modulation circuit;

[0054] The modulation circuit is used for converting the sine wave signal into a pulse width modulation signal whose pulse width is proportional to the measured displacement.

[0055] In addition, in the embodiment, an inductive displacement sensor is also disclosed, comprising:

[0056] The pulse width detection circuit and the signal conditioning circuit connected with the pulse width detection circuit;

[0057] The signal conditioning circuit is used for converting the pulse width modulation signal output by the pulse width detection circuit and proportional to the measured displacement into a voltage signal whose size is proportional to the measured displacement.

[0058] The pulse width detection circuit and the inductive displacement sensor in the application comprise an oscillation circuit, a coil resonance circuit and a modulation circuit; the output end of the oscillation circuit is connected with the input end of the coil resonance circuit, and the output end of the coil resonance circuit is connected with the modulation circuit; the oscillation circuit is used for generating a driving square wave signal and outputting the driving square wave signal to the coil resonance circuit; the coil resonance circuit is used for generating a sine wave signal with the same frequency as the driving square wave signal and outputting the sine wave signal to the modulation circuit; and the modulation circuit is used for converting the sine wave signal into a pulse width modulation signal whose pulse width is proportional to the measured displacement. Compared with the prior art, the application adopts the mode of converting the amplitude change of the probe sine wave into a pulse width modulation wave for detection, which can improve the signal-to-noise ratio and the anti-interference ability of the inductive displacement sensor detection. Only an RC integration smoothing circuit and a normalization circuit are needed to condition the signal required by the user.

[0059] Embodiment two:

[0060] Embodiment two is a preferred embodiment of embodiment one, which is different from embodiment one in that the specific structure of the inductive displacement sensor and the pulse width detection circuit thereof is introduced, and specifically comprises the following contents:

[0061] In the embodiment, as shown in Figure 1 An inductive displacement sensor is disclosed, comprising: a pulse width detection circuit and a signal conditioning circuit;

[0062] The pulse width detection circuit comprises: an oscillation circuit composed of a crystal oscillator CY1 and a quadrature phase shifter IC1, a coil resonance circuit composed of a probe coil L1 and a resonance capacitor C1, and a modulation circuit composed of an inverter IC2, an XOR gate IC3 and an isolation capacitor C2; the signal conditioning circuit comprises: a smoothing filter circuit composed of an integration resistor R1 and an integration capacitor C3, and a normalization circuit composed of a gain resistor R2, a gain resistor R3 and a normalization conditioning circuit IC4;

[0063] The output terminal of the crystal oscillator CY1 is connected with the input terminal of the quadrature phase shifter IC1; the quadrature phase shifter IC1 comprises a first output terminal and a second output terminal, and the first output terminal is connected with the input terminal of the coil resonance circuit; the probe coil L1 and the resonance capacitor C1 construct a parallel resonance circuit, and the first end of the parallel resonance circuit is connected with the first output terminal of the phase shifter IC1 and the first input terminal of the modulation circuit respectively, and the second end of the parallel resonance circuit is grounded; the first end of the isolation capacitor C2 is connected with the first end of the parallel resonance circuit, the second end of the isolation capacitor is connected with the input terminal of the inverter IC2, the output terminal of the inverter IC2 is connected with the first input terminal of the exclusive-OR gate IC3, and the second input terminal of the exclusive-OR gate IC3 is connected with the second end of the quadrature phase shifter IC1; the first end of the integration resistor R1 is connected with the output terminal of the exclusive-OR gate IC3, the second end is connected with the first end of the integration capacitor C3, and the second end of the integration capacitor C3 is grounded. The first input terminal of the normalization conditioning circuit IC4 is connected with the first end of the integration capacitor C3, the second input terminal of the normalization conditioning circuit IC4 is connected with the first end of the gain resistor R2 and the first end of the gain resistor R3 respectively, the second end of the gain resistor R2 is grounded, and the second end of the gain resistor R3 is connected with the output terminal of the normalization conditioning circuit IC4.

[0064] In the embodiment, the working process of the inductive displacement sensor is as follows:

[0065] Step 1: a square wave pulse of 300 KHz to 1 MHz is provided by the crystal oscillator CY1 into the square wave 90° phase shifter IC1, wherein the square wave pattern output by the crystal oscillator is as shown in Figure 2 .

[0066] Step 2: the square wave 90° phase shifter IC1 converts the square wave pulse into two-way orthogonal square wave signals with a phase of 90°, the square wave signal with a phase of 90° drives the probe coil and the resonance capacitor C1 connected in parallel with the probe coil L1, and the signal with a phase of 0° is input to one input terminal of the exclusive-OR gate IC3; wherein the two-way orthogonal square wave signals with a phase of 90° output by the phase shifter IC1 are as shown in Figure 3 .

[0067] Step 3: since the probe coil L1 and the resonance capacitor C1 jointly act on the resonance frequency which is the same as the frequency of the square wave signal, a sinusoidal signal with the same frequency as the square wave signal is output at both ends of the probe coil L1; and the amplitude of the sinusoidal signal is proportional to the gap between the probe coil L1 and the measured target object, that is, the larger the gap between the probe coil L1 and the measured target object, the larger the amplitude of the sinusoidal signal, and the smaller the gap between the probe coil L1 and the measured target object, the smaller the amplitude of the sinusoidal signal. Wherein the sinusoidal resonance waveform at both ends of the probe coil L1 is as shown in Figure 4 .

[0068] Step 4, the sine wave signal is sent to the inverter IC2 after being isolated from the direct current signal by the direct current isolation capacitor C2 to perform the inverting operation as shown in the figure Figure 5 , and output a pulse width modulation signal PWM1 with a pulse width inversely proportional to the amplitude of the sine wave, and the waveform of the pulse width modulation signal PWM1 is shown in the figure Figure 6 ; wherein the direct current isolation capacitor C2 is used to isolate the direct current component in the sine wave generated by the LC sine wave resonance circuit composed of the probe coil L1 and the resonance capacitor C1; the inverter IC2 performs threshold level comparison and inversion on the sine wave signal output by the direct current isolation capacitor C2, and outputs a low level when the amplitude of the sine wave signal is greater than the threshold level, and outputs a high level when the amplitude of the sine wave signal is less than the threshold level. The signal output by the inverter IC2 has a pulse width inversely proportional to the amplitude of the sine signal, which is a pulse width modulation signal PWM1. Correspondingly, the pulse width is inversely proportional to the gap between the probe coil L1 and the measured target object, that is, the greater the gap between the probe coil L1 and the measured target object, the greater the amplitude of the sine wave and the smaller the pulse width, and the smaller the gap between the probe coil L1 and the measured target object, the smaller the amplitude of the sine wave and the greater the pulse width. Wherein, the inverting operation of the probe sine wave signals with different amplitudes is shown in Figure 9 and Figure 11 ; the pulse width comparison of the inverting operation of the probe sine wave signals with different amplitudes is shown in Figure 13 ;

[0069] In order to more intuitively verify the technical scheme, the present application uses mulitisim software for simulation debugging, as shown in Figure 15 , Figure 16 , Figure 17 ; wherein in the three figures, the square wave on the left is the square wave with a phase of 0° output by the 90° phase shifter IC1, and the sine wave is the sine wave generated when the probe L1 resonates. The square wave on the right is the square wave with a phase of 0° output by the 90° phase shifter IC1. The middle modulation wave represents the pulse width modulation waveform PWM1 obtained after the inverter IC2 performs inverting operation on the sine wave of the probe coil L1.

[0070] Due to the diversity of technical routes, the circuit for realizing the pulse width modulation waveform can also be realized by using an operational amplifier, a special comparator, and other circuits, and the way of realizing the same pulse width modulation square wave by using other circuits should be protected.

[0071] Step 5, the pulse width modulation waveform PWM1 and another 0° phase signal output by the square wave 90° phase shifter IC1 are input to the exclusive OR operation circuit IC3 to perform the operation as shown in the figure Figure 7The XOR operation shown generates another pulse width modulation signal PWM2 whose pulse width is proportional to the amplitude of the sine wave; that is, the greater the gap between the probe coil L1 and the measured target object, the greater the amplitude of the sine wave and the greater the pulse width, and the smaller the gap between the probe coil L1 and the measured target object, the smaller the amplitude of the sine wave and the smaller the pulse width. Among them,

[0072] The XOR operation of the probe sine wave signals with different amplitudes is as shown in Figure 10 、 Figure 12 ; and the pulse width after the XOR operation of the probe sine wave signals with different amplitudes is as shown in Figure 14 .

[0073] In order to more intuitively verify the technical scheme, the present application uses mulitisim software for simulation debugging, as shown in Figure 15 、 Figure 16 、 Figure 17 ; among the three figures, the lower modulation wave represents the pulse width modulation waveform PWM2 obtained by XOR operation on the square wave with a phase of 0° output by the 90° phase shifter IC1 and the pulse width modulation waveform PWM1 obtained by inverting operation of the inverter IC2;

[0074] Step 6, the pulse width modulation signal after the XOR operation is output after being smoothed by the integral circuit of R1 and C1, and a voltage signal proportional to the gap between the probe coil L1 and the measured target object is obtained. That is, the integral resistor R1 and the integral capacitor C3 together constitute an RC integral smoothing filter circuit, which smoothes the pulse width modulation signal PWM2, removes the pulsating component, and outputs a direct current voltage value proportional to the gap between the probe coil L1 and the measured target object. That is, the greater the gap between the probe coil L1 and the measured target object, the greater the amplitude of the sine wave and the greater the direct current voltage, and the smaller the gap between the probe coil L1 and the measured target object, the smaller the amplitude of the sine wave and the smaller the direct current voltage. Among them, the RC integral smoothing waveform is as shown in Figure 8 ;

[0075] Step 7, the voltage signal is output by the normalization adjustment circuit IC4 in the output mode required by the user for the user to use. The normalization conditioning circuit IC4, R2 and R3 amplify and shift the direct current signal after the integral smoothing filter, and normalize it into the output mode required by the user.

[0076] In summary, the pulse width detection circuit and the inductive displacement sensor include an oscillation circuit, a coil resonance circuit and a modulation circuit; the output end of the oscillation circuit is connected with the input end of the coil resonance circuit, and the output end of the coil resonance circuit is connected with the modulation circuit; the oscillation circuit is used for generating a driving square wave signal and outputting the driving square wave signal to the coil resonance circuit; the coil resonance circuit is used for generating a sine wave signal with the same frequency as the driving square wave signal and outputting the sine wave signal to the modulation circuit; and the modulation circuit is used for converting the sine wave signal into a pulse width modulation signal with the pulse width being proportional to the measured displacement. Compared with the prior art, the present application converts the amplitude change of the probe sine wave into a pulse width modulation wave for detection, which can improve the signal-to-noise ratio and anti-interference capability of the inductive displacement sensor detection, so that the resolution can reach nanometers or even angstroms. Only an RC integration smoothing circuit and a normalization circuit are needed to condition the signal required by the user, and in addition, the present application also has the characteristics of clear principle, simple circuit and simple debugging.

[0077] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A pulse width detection circuit for use in an inductive displacement sensor, characterized by, The oscillation circuit, the coil resonance circuit and the modulation circuit are included; the output end of the oscillation circuit is connected with the input end of the coil resonance circuit, and the output end of the coil resonance circuit is connected with the modulation circuit; The oscillation circuit is used for generating a driving square wave signal and outputting the driving square wave signal to the coil resonance circuit; The coil resonance circuit is used for generating a sine wave signal with the same frequency as the driving square wave signal and outputting the sine wave signal to the modulation circuit; The modulation circuit is used for converting the sine wave signal into a pulse width modulation signal with the pulse width being proportional to the measured displacement; the oscillation circuit includes a crystal oscillator CY1 and a quadrature phase shifter IC1; the output end of the crystal oscillator CY1 is connected with the input end of the quadrature phase shifter IC1; the quadrature phase shifter IC1 includes a first output end and a second output end, the first output end of the quadrature phase shifter IC1 is connected with the input end of the coil resonance circuit, and the second output end of the quadrature phase shifter IC1 is connected with the modulation circuit; The crystal oscillator CY1 is used for outputting a square wave pulse to the quadrature phase shifter IC1; the quadrature phase shifter IC1 is used for converting the square wave pulse into a first square wave signal and a second square wave signal with the phases being orthogonal, outputting the first square wave signal as a driving square wave signal to the coil resonance circuit, and outputting the second square wave signal to the modulation circuit; the coil resonance circuit includes a probe coil L1 and a resonance capacitor C1, and the probe coil L1 and the resonance capacitor C1 constitute a parallel resonance circuit; the first end of the parallel resonance circuit is connected with the first output end of the quadrature phase shifter IC1 and the first input end of the modulation circuit respectively, and the second end of the parallel resonance circuit is grounded; the parallel resonance circuit is used for generating a sine wave signal with the same frequency as the driving square wave signal at the two ends of the probe coil L1 and outputting the sine wave signal to the modulation circuit; the modulation circuit includes an inverter IC2, an exclusive OR gate IC3 and an isolation capacitor C2; the first end of the isolation capacitor C2 is connected with the first end of the parallel resonance circuit, the second end of the isolation capacitor C2 is connected with the input end of the inverter IC2, the output end of the inverter IC2 is connected with the first input end of the exclusive OR gate IC3, and the second input end of the exclusive OR gate IC3 is connected with the second output end of the quadrature phase shifter IC1; The isolation capacitor C2 is used for isolating the direct current component in the sine wave signal and outputting the isolated sine wave signal to the inverter IC2; The inverter IC2 is used for performing inversion processing on the isolated sine wave signal and outputting the inversion-processed sine wave signal to the exclusive OR gate IC3; the exclusive OR gate IC3 is used for performing exclusive OR processing on the inversion-processed sine wave signal and the second square wave signal to obtain a pulse width modulation signal with the pulse width being proportional to the measured displacement; The square wave pulse frequency output by the crystal oscillator CY1 is 300KHz-1MHz, the phase of the first square wave signal output by the first output end of the quadrature phase shifter IC1 is 90 degrees, and the phase of the second square wave signal output by the second output end of the quadrature phase shifter IC1 is 0 degrees.

2. An inductive displacement sensor, characterized by Comprise: The pulse width detection circuit of claim 1 and a signal conditioning circuit connected with the pulse width detection circuit; The signal conditioning circuit is used for converting the pulse width modulation signal output by the pulse width detection circuit, whose pulse width is proportional to the measured displacement, into a voltage signal whose size is proportional to the measured displacement.

3. An inductive displacement sensor according to claim 2, characterised in that, The signal conditioning circuit comprises a smoothing filter circuit and a normalization circuit, the input end of the smoothing filter circuit is connected with the output end of the pulse width detection circuit, and the output end of the smoothing filter circuit is connected with the input end of the normalization circuit; The smoothing filter circuit is used for smoothing filtering the pulse width modulation signal output by the pulse width detection circuit, whose pulse width is proportional to the measured displacement, to remove the pulsating component and obtain a direct current voltage value whose size is proportional to the measured displacement; The normalization circuit is used for amplifying and shifting the direct current voltage value to normalize it into a preset output mode.

4. An inductive displacement sensor according to claim 3, characterised in that, The smoothing filter circuit comprises an integral resistor R1 and an integral capacitor C3, the first end of the integral resistor R1 is connected with the output end of the pulse width detection circuit, the second end of the integral resistor R1 is connected with the first end of the integral capacitor C3, and the second end of the integral capacitor C3 is grounded.

5. An inductive displacement sensor according to claim 4, characterised in that, The normalization circuit comprises a gain resistor R2, a gain resistor R3 and a normalization conditioning circuit IC4, the first input end of the normalization conditioning circuit IC4 is connected with the first end of the integral capacitor C3, the second input end of the normalization conditioning circuit IC4 is respectively connected with the first end of the gain resistor R2 and the gain resistor R3, the second end of the gain resistor R2 is grounded, and the second end of the gain resistor R3 is connected with the output end of the normalization conditioning circuit IC4.

6. An inductive displacement sensor according to claim 5, characterised in that, The normalization conditioning circuit IC4 is an operational amplifier.

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