An eddy current displacement sensor linearization method based on exponential carrier pulse width modulation

Abstract

This invention discloses a linearization method for eddy current displacement sensors based on exponential carrier pulse width modulation (PWM). This method addresses the problem of limited linear measurement range of the output voltage of eddy current displacement sensors. First, the displacement-voltage characteristic curve of the eddy current displacement sensor is measured. Then, a linearization circuit based on exponential carrier PWM is constructed, and the circuit parameters are adjusted so that the shape of the exponential carrier is identical to the displacement-voltage characteristic curve of the eddy current displacement sensor. The output voltage of the eddy current displacement sensor to be linearized and the exponential carrier are pulse-width modulated (PWM). A standard PWM waveform is obtained by passing it through a double inverter, then filtered in a low-pass filter, and finally the linearized voltage of the eddy current displacement sensor is output. This invention effectively improves the linearity of eddy current displacement sensors, enabling them to have a wider linear measurement range within a given measurement range.

Description

Technical Field

[0001] This invention relates to the field of eddy current displacement measurement technology, specifically to a linearization method for eddy current displacement sensors based on exponential carrier pulse width modulation. Background Technology

[0002] Eddy current displacement sensors are devices that use the principle of eddy currents to perform non-contact measurement of the displacement of metallic materials. They have advantages such as high sensitivity, good frequency response characteristics, simple structure, and are not affected by non-metallic materials. They have been widely used in electromechanical equipment, aerospace, shipbuilding and other fields.

[0003] The output voltage of an eddy current displacement sensor varies with the distance between the object being measured and the probe. Within a certain distance range, the sensor's output voltage changes linearly with distance. However, when the distance exceeds a certain range, the output voltage no longer changes linearly; this characteristic is called the nonlinearity of the eddy current displacement sensor. The linear measurement range of an eddy current displacement sensor is related to the outer diameter of the probe coil, typically ranging from 1 / 3 to 1 / 5 of the outer diameter. In many fields, it is desirable to expand the linear measurement range of the sensor without increasing the probe's outer diameter, or to improve the sensor's linearity within a specific measurement range. Therefore, it is necessary to linearize the output of the eddy current displacement sensor.

[0004] To extend the linear measurement range of eddy current displacement sensors, several methods are currently employed. First, once the eddy current displacement sensor enters the nonlinear region, the amplitude of the high-frequency excitation source is adjusted accordingly to compensate for the nonlinearity as the measurement distance changes. Second, a digital method is used, with linearization processing performed in a digital signal processor. Third, a linearization circuit is connected in series at the sensor output, such as a multi-stage correction circuit based on diode voltage-current characteristics or an exponential compensation circuit based on transistors. The first method is difficult to implement because it's challenging to establish the relationship between real-time voltage amplitude and output nonlinearity in analog circuits. The second method requires simultaneous design of analog and digital circuits, significantly increasing sensor cost due to the use of processor chips. The third method is commonly used, but most current methods rely on complex high-order power corrections or include numerous temperature-sensitive nonlinear components such as diodes and transistors, still exhibiting many shortcomings. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a linearization method for eddy current displacement sensors based on exponential carrier pulse width modulation, which improves the linearity of the displacement-voltage characteristic curve of the eddy current displacement sensor and expands the linear measurement range of the sensor.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation, the method comprising the following steps:

[0008] (1) Based on the input-output characteristics of the eddy current displacement sensor, the displacement-voltage characteristic curve of the eddy current displacement sensor is measured, and the curve is subjected to exponential fitting to obtain the exponential characteristic curve of the eddy current displacement sensor.

[0009] (2) Construct a linearization circuit based on exponential carrier pulse width modulation. Specifically, use an exponential carrier generator to obtain a carrier signal, and then perform pulse width modulation on the modulated wave signal to obtain a linearization circuit based on exponential carrier pulse width modulation.

[0010] (3) The voltage signal that needs to be linearized is compared with the carrier signal of the linearization circuit based on exponential carrier pulse width modulation to obtain the PWM signal. The standard PWM wave is obtained through a double inverter, then filtered in a low-pass filter, and finally the voltage of the linearized eddy current displacement sensor is output.

[0011] Further, step (1) specifically involves: measuring the displacement d–voltage U characteristic curve U=f(d) of the eddy current displacement sensor, and determining the starting point d0 and interval length Δd of the linear measurement interval of the sensor based on the technical requirements of the eddy current displacement sensor and the curve of U=f(d).

[0012] Further, step (2) specifically involves: constructing a linearization circuit based on exponential carrier pulse width modulation, wherein the generated carrier must meet the following conditions: the shape of the curve of the rising region of the carrier within one period should coincide as much as possible with the shape of the displacement-voltage characteristic curve of the eddy current displacement sensor to be linearized within the linearization interval; design an exponential carrier generation circuit based on the displacement-voltage exponential characteristic curve of the eddy current displacement sensor obtained in step (1), and adjust the parameters of the circuit to make the carrier shape meet the aforementioned conditions.

[0013] Further, step (3) specifically involves using a comparator to linearize the voltage signal U that needs to be linearized. d and the carrier signal U based on the linearization circuit of exponential carrier pulse width modulation k When comparing, when U d >U k When U is high, the comparator outputs a high level; when U is high, the comparator outputs a high level. d k When the comparator outputs a low level, the comparator outputs a PWM waveform with alternating high and low levels, which is then filtered by a low-pass filter and finally outputs the linearized voltage of the eddy current displacement sensor.

[0014] ​Furthermore, a carrier wave is generated using an exponential carrier wave generator circuit, which consists of an inverting hysteresis comparator A, a carrier capacitor C, voltage divider resistors R1 and R2, a charging resistor R3, a discharging resistor R4, Schottky diodes D1 and D2, a current-limiting resistor R0, and a reverse series Zener diode D. z The circuit consists of a charging resistor R3, a discharging resistor R4, and Schottky diodes D1 and D2 forming the charging and discharging circuit for the carrier capacitor C. The inverting input of the inverting hysteresis comparator A is connected to the carrier capacitor C, and the non-inverting input is connected to a voltage divider circuit composed of voltage divider resistors R1 and R2. The output of A is connected to the charging and discharging circuit of the carrier capacitor C, the voltage divider circuit, and the reverse series Zener diode D through a current-limiting resistor R0. z .

[0015] Furthermore, the operating principle of the exponential carrier generation circuit is as follows: when the circuit is powered on, due to the presence of noise, assuming the non-inverting input of the inverting hysteresis comparator A is a positive voltage, since the voltage at the non-inverting input is higher than that at the inverting input, the inverting hysteresis comparator A outputs a positive high level; through the voltage divider circuit, the voltage at the non-inverting input is the positive threshold voltage; the carrier capacitor C is charged through the Schottky diode D1 and the charging resistor R3, increasing the voltage of the carrier capacitor C, and consequently increasing the voltage at the inverting input; when the voltage at the inverting input rises to a level higher than that at the non-inverting input, i.e., the positive threshold voltage... When the voltage is high, the inverting hysteresis comparator A outputs a negative low level. Through the voltage divider circuit composed of two resistors, the voltage at the non-inverting input is the negative threshold voltage. Subsequently, the carrier capacitor C discharges through the discharge resistor R4 and the Schottky diode D2, and the voltage of the carrier capacitor C decreases, as does the voltage at the inverting input. When the voltage at the inverting input is lower than the voltage at the non-inverting input, i.e., the negative threshold voltage, the inverting hysteresis comparator A outputs a positive high level. This cycle repeats continuously. Since the voltage of the capacitor charging and discharging follows an exponential law, the voltage of the carrier capacitor C is a periodic exponential waveform.

[0016] Furthermore, the shape of the exponential carrier is changed by altering the ratio of the voltage divider resistors R1 and R2, and the values ​​of the charging resistor R3 and the discharging resistor R4. In order to make the most of the exponential carrier waveform in the charging interval, the discharging resistor R4 is much smaller than the charging resistor R3. The shape of the exponential carrier in the rising interval is changed by altering the ratio of the voltage divider resistors R1 and R2, so that the shape of the exponential carrier coincides as closely as possible with the exponential characteristic curve of the eddy current displacement sensor obtained in step (1).

[0017] Furthermore, in step (3), the pulse modulation wave obtained by the comparator passes through a double inverter and outputs a full-amplitude PWM signal with the same amplitude as the power supply. Then, a third-order RC series filter is used for low-pass filtering to finally obtain the linearized voltage output.

[0018] Furthermore, changing the ratio of the voltage divider R1 and R2 not only alters the shape of the exponential carrier but also its frequency. Under the condition of satisfying the linearization requirement, increasing the ratio of R1 and R2 can increase the frequency of the exponential carrier, which can reduce the output noise after low-pass filtering.

[0019] Furthermore, the following preamplifier circuit is used as the eddy current displacement sensor. This preamplifier circuit consists of a signal generator, a probe resonant circuit, a phase-sensitive detector, a micro-signal amplifier, and a bias circuit. The signal generator generates an excitation wave for the eddy current displacement sensor. The voltage waveform obtained by inputting the excitation wave into the probe resonant circuit passes through a phase-sensitive detector composed of an inverter and a high-speed analog switch. After detection, noise with a frequency different from that of the original circuit is filtered out. Then, through the micro-signal amplifier and the bias circuit, the output voltage of the unlinearized eddy current displacement sensor is obtained.

[0020] The beneficial effects of the present invention are: the present invention can effectively improve the linearity of the eddy current displacement sensor, so that the eddy current displacement sensor has a wider linear measurement range within a given measurement range. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of the linearization circuit for the eddy current displacement sensor based on exponential carrier pulse width modulation of the present invention.

[0022] Figure 2 This is a structural diagram of the exponential carrier generation circuit of the present invention.

[0023] Figure 3 Schematic diagram of the voltage waveform of carrier capacitor C

[0024] Figure 4 This is a circuit diagram of the preamplifier for an eddy current displacement sensor using the exponential carrier pulse width modulation linearization method of this invention.

[0025] Figure 5 The figure shows the displacement-output voltage characteristic of an eddy current displacement sensor without linearization.

[0026] Figure 6 This is a schematic diagram comparing the exponential carrier shape of an eddy current displacement sensor with the unlinearized voltage characteristics.

[0027] Figure 7 The figure shows the displacement-output voltage characteristic of an eddy current displacement sensor after linearization. Detailed Implementation

[0028] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] This invention provides a linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation, the specific steps of which are as follows:

[0030] Step (1): Based on the input-output characteristics of the eddy current displacement sensor, measure the displacement-voltage characteristic curve of the eddy current displacement sensor, and perform exponential fitting on the curve to obtain the exponential characteristic curve of the eddy current displacement sensor; specifically, measure the displacement d-voltage U characteristic curve U=f(d) of the eddy current displacement sensor, and determine the starting point d0 and the interval length △d of the linear measurement interval of the displacement-voltage characteristic curve according to the technical requirements of the eddy current displacement sensor and the curve of U=f(d).

[0031] Step (2): Construct a linearization circuit based on exponential carrier pulse width modulation; this circuit uses an exponential carrier generator to obtain a carrier signal, and then performs pulse width modulation on the modulated wave signal to obtain a linearization circuit based on exponential carrier pulse width modulation; specifically, construct a linearization circuit based on exponential carrier pulse width modulation, and the generated carrier must meet the condition that the curve shape of the rising region of the carrier in one period coincides as much as possible with the shape of the displacement-voltage characteristic curve of the eddy current displacement sensor in the linearization interval. Based on the exponential characteristic curve of the eddy current displacement sensor obtained in step (1), design the exponential carrier generation circuit, and adjust the circuit parameters to make the carrier shape meet the aforementioned conditions.

[0032] Step (3): Compare the voltage signal to be linearized with the carrier signal of the linearization circuit based on exponential carrier pulse width modulation to obtain the pulse width modulation (PWM) signal. This PWM signal is then filtered by a low-pass filter, and finally, the linearized voltage of the eddy current displacement sensor is output. Specifically, a comparator is used to convert the voltage signal U to be linearized... d and the carrier signal U based on the linearization circuit of exponential carrier pulse width modulation k When comparing, when U d >U k When U is high, the comparator outputs a high level; when U is high, the comparator outputs a high level. d k When the comparator outputs a low level, the comparator outputs a PWM waveform with alternating high and low levels. This waveform is then filtered by a low-pass filter, and finally outputs the linearized voltage of the eddy current displacement sensor.

[0033] like Figure 1 As shown, this invention provides a linearization circuit for an eddy current displacement sensor based on exponential carrier pulse width modulation. The circuit consists of an exponential carrier generator, PWM modulation, and a low-pass filter. Specifically, it comprises the following three steps:

[0034] Step (1): Input the voltage modulation wave of the eddy current displacement sensor into the linearization circuit. ​

[0035] Step (2): Pulse-modulate the PWM wave generated by the exponential carrier generator with the voltage modulation wave. Use a comparator to convert the voltage signal U that needs to be linearized. d and the carrier signal U based on the linearization circuit of exponential carrier pulse width modulation k When comparing, when U d >U k When U is high, the comparator outputs a high level; when U is high, the comparator outputs a high level. d k When the comparator outputs a low level, the comparator outputs a PWM waveform with alternating high and low levels.

[0036] Step (3): The modulated PWM wave is passed through a double inverter to obtain a standard PWM waveform with the power supply voltage. Then, it is filtered in a low-pass filter, and finally the linearized voltage of the eddy current displacement sensor is output. The filter cutoff frequency is determined by the dynamic characteristics required by the eddy current displacement sensor.

[0037] like Figure 2 As shown, the exponential carrier generation circuit of the present invention consists of an inverting hysteresis comparator A, a carrier capacitor C, voltage divider resistors R1 and R2, a charging resistor R3, a discharging resistor R4, Schottky diodes D1 and D2, a current-limiting resistor R0, and a reverse series Zener diode D1. z Composition. ±Vz represents the positive and negative regulated voltages of Dz.

[0038] The structure of the exponential carrier generator circuit is as follows: the inverting input of the inverting hysteresis comparator A is connected to the carrier capacitor C; the non-inverting input of A is connected to a voltage divider circuit consisting of voltage divider resistors R1 and R2; and the output of A is connected to the charging and discharging circuit of the carrier capacitor C, the voltage divider circuit, and the reverse series Zener diode D through the current-limiting resistor R0. z The charging resistor R3, the discharging resistor R4, and the Schottky diodes D1 and D2 constitute the charging and discharging circuit for the carrier capacitor C.

[0039] ​The principle of the exponential carrier generation circuit of this invention is as follows: When the circuit is powered on, due to the presence of noise, it is assumed that the non-inverting input of the inverting hysteresis comparator A is at a positive voltage. Since the voltage at the non-inverting input is higher than that at the inverting input, the inverting hysteresis comparator A outputs a positive high level. Through a voltage divider circuit, the voltage at the non-inverting input is the positive threshold voltage. The carrier capacitor C is charged through Schottky diode D1 and charging resistor R3, increasing the voltage of the carrier capacitor C and consequently increasing the voltage at the inverting input. When the voltage at the inverting input rises above the voltage at the non-inverting input, i.e., the positive threshold voltage, the inverting hysteresis comparator A outputs a negative low level. Through a voltage divider circuit composed of two resistors, the voltage at the non-inverting input is the negative threshold voltage. Subsequently, the carrier capacitor C is discharged through discharge resistor R4 and Schottky diode D2, decreasing the voltage of the carrier capacitor C and consequently decreasing the voltage at the inverting input. When the voltage at the inverting input is lower than the voltage at the non-inverting input, i.e., the negative threshold voltage, the inverting hysteresis comparator A outputs a positive high level. This cycle repeats itself continuously. Because the voltage of the capacitor charges and discharges according to an exponential law, the voltage of the carrier capacitor C exhibits a periodic exponential waveform. For example... Figure 3 The figure shows the voltage waveform of the carrier capacitor C. TH and V TL T represents the positive and negative threshold voltages of the carrier capacitor C. H and T L These are the charging and discharging times of the carrier capacitor C, respectively.

[0040] like Figure 4 As shown, this invention provides a preamplifier circuit using a linearization method based on exponential carrier pulse width modulation as an implementation of an eddy current displacement sensor. This preamplifier circuit consists of a signal generator, a probe resonant circuit, a phase-sensitive detector, a micro-signal amplifier and bias circuit, an exponential carrier generator, PWM modulation, a low-pass filter, and an output section. First, the signal generator generates an excitation wave for the eddy current displacement sensor. The voltage waveform obtained by inputting the excitation wave to the probe resonant circuit passes through a phase-sensitive detector composed of an inverter and a high-speed analog switch, filtering out noise with frequencies different from the original circuit. Then, through the micro-signal amplifier and bias circuit, the output voltage of the unlinearized eddy current displacement sensor is obtained. Next, an exponential carrier is generated by the exponential carrier generator and PWM modulated with the unlinearized output voltage. Finally, the modulated waveform is low-pass filtered to obtain the final linearized output voltage of the eddy current displacement sensor.

[0041] Since the amplitude of the comparator's output PWM waveform is not necessarily constant, a double inverter is used to adjust the modulated PWM waveform to a standard PWM waveform with the full power supply voltage amplitude output.

[0042] The displacement-output voltage characteristic of an eddy current displacement sensor without linearization is as follows: Figure 5 As shown, when without linearization, the output voltage characteristic basically shows exponential change with the increase of distance, with poor linearity, small linear measurement range, and unable to meet the requirements of linear measurement.

[0043] As Figure 6 shown, in the present invention, the voltage division resistance parameters of the exponential carrier generator should be adjusted, aiming to adjust the threshold voltage so that the waveform of the exponential carrier has a similar shape to the voltage characteristic of the non-linearized eddy current displacement sensor.

[0044] Changing the ratio of the voltage division resistors R1 and R2 not only changes the shape of the exponential carrier but also changes the frequency of the exponential carrier. Under the condition of meeting the linearization requirements, increasing the ratio of R1 and R2 can increase the frequency of the exponential carrier, and the output noise can be reduced after low-pass filtering. By adjusting the small-signal amplifier and the bias circuit of the preamplifier circuit, at the minimum measured distance and the maximum measured distance of the eddy current displacement sensor, the duty cycle of PWM should be close to 0% and 100% respectively.

[0045] The displacement–output voltage characteristic of a certain eddy current displacement sensor after linearization is as Figure 7 shown. After using the linearization method of the present invention, the sensor has good linearity in the range of 0.3 < d < 1.3 mm.

[0046] When conducting the actual circuit design, the threshold voltages V TH and V TL for capacitor charging and discharging are adjusted by connecting a potentiometer and a resistor in series to adapt to different probes and different magnetic permeability characteristics of the measured metal. During debugging, each adjustment requires measuring the voltage–displacement characteristic curve of the eddy current displacement sensor, and appropriately adjusting the potentiometer according to the bending direction and degree of the curve to complete the calibration of the current probe and the current measured metal material.

[0047] The above examples are used to explain and illustrate the present invention rather than limit the present invention. Any modification and change made within the spirit and protection scope of the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation, characterized in that: (1) Based on the input-output characteristics of the eddy current displacement sensor, the displacement-voltage characteristic curve of the eddy current displacement sensor is measured, and the curve is subjected to exponential fitting to obtain the exponential characteristic curve of the eddy current displacement sensor. (2) Construct a linearization circuit based on exponential carrier pulse width modulation. Specifically, use an exponential carrier generator to obtain a carrier signal, and then perform pulse width modulation on the modulated wave signal to obtain a linearization circuit based on exponential carrier pulse width modulation. The generated carrier must meet the following conditions: the curve shape of the rising region of the carrier in one period should coincide as much as possible with the shape of the displacement-voltage characteristic curve of the eddy current displacement sensor to be linearized in the linearization interval. Design an exponential carrier generation circuit based on the displacement-voltage exponential characteristic curve of the eddy current displacement sensor obtained in step (1), and adjust the parameters of the circuit to make the carrier shape meet the aforementioned conditions. (3) The voltage signal that needs to be linearized is compared with the carrier signal of the linearization circuit based on exponential carrier pulse width modulation to obtain the PWM signal. The standard PWM wave is obtained through a double inverter, then filtered in a low-pass filter, and finally the voltage of the linearized eddy current displacement sensor is output.

2. The linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation according to claim 1, characterized in that: Step (1) specifically involves measuring the displacement d–voltage U characteristic curve U=f(d) of the eddy current displacement sensor, and determining the starting point d0 and interval length Δd of the linear measurement interval of the sensor based on the technical requirements of the eddy current displacement sensor and the curve of U=f(d).

3. The linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation according to claim 1, characterized in that: Step (3) specifically involves using a comparator to linearize the voltage signal U that needs to be linearized. d and the carrier signal U based on the linearization circuit of exponential carrier pulse width modulation k When comparing, when U d >U k When U is high, the comparator outputs a high level; when U is high, the comparator outputs a high level. d k When the comparator outputs a low level, the comparator outputs a PWM waveform with alternating high and low levels, which is then filtered by a low-pass filter and finally outputs the linearized voltage of the eddy current displacement sensor.​ 4. The linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation according to claim 1, characterized in that: The carrier wave is generated by an exponential carrier wave generator circuit, which consists of an inverting hysteresis comparator A, a carrier capacitor C, voltage divider resistors R1 and R2, a charging resistor R3, a discharging resistor R4, Schottky diodes D1 and D2, a current-limiting resistor R0, and a reverse series Zener diode D. z The circuit consists of a charging resistor R3, a discharging resistor R4, and Schottky diodes D1 and D2 forming the charging and discharging circuit for the carrier capacitor C. The inverting input of the inverting hysteresis comparator A is connected to the carrier capacitor C, and the non-inverting input is connected to a voltage divider circuit composed of voltage divider resistors R1 and R2. The output of A is connected to the charging and discharging circuit of the carrier capacitor C, the voltage divider circuit, and the reverse series Zener diode D through a current-limiting resistor R0. z .

5. The linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation according to claim 4, characterized in that: The exponential carrier generation circuit works as follows: When the circuit is powered on, due to the presence of noise, assuming the non-inverting input of the inverting hysteresis comparator A is at a positive voltage, since the voltage at the non-inverting input is higher than that at the inverting input, the inverting hysteresis comparator A outputs a positive high level. Through the voltage divider circuit, the voltage at the non-inverting input is the positive threshold voltage. The carrier capacitor C is charged through the Schottky diode D1 and the charging resistor R3, increasing the voltage of the carrier capacitor C and thus increasing the voltage at the inverting input. When the voltage at the inverting input rises to a level higher than that at the non-inverting input, i.e., the positive threshold voltage, the inverting hysteresis comparator A outputs a negative low level. Through the voltage divider circuit composed of two resistors, the voltage at the non-inverting input is the negative threshold voltage. Subsequently, the carrier capacitor C is discharged through the discharge resistor R4 and the Schottky diode D2, decreasing the voltage of the carrier capacitor C and thus decreasing the voltage at the inverting input. When the voltage at the inverting input is lower than the voltage at the non-inverting input, i.e., the negative threshold voltage, the inverting hysteresis comparator A outputs a positive high level; this cycle repeats continuously. Since the voltage of the capacitor charging and discharging follows an exponential law, the voltage of the carrier capacitor C is a periodic exponential waveform.

6. The linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation according to claim 4, characterized in that: The shape of the exponential carrier is changed by altering the ratio of the voltage divider resistors R1 and R2, and the values ​​of the charging resistor R3 and the discharging resistor R4. To make the best use of the exponential carrier waveform in the charging interval, the discharging resistor R4 is much smaller than the charging resistor R3. The shape of the exponential carrier in the rising interval is changed by altering the ratio of the voltage divider resistors R1 and R2, so that the shape of the exponential carrier coincides as closely as possible with the exponential characteristic curve of the eddy current displacement sensor obtained in step (1).

7. The linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation according to claim 1, characterized in that: In step (3), the pulse modulation wave obtained by the comparator passes through a double inverter and outputs a full-amplitude PWM signal with the same amplitude as the power supply. Then, a third-order RC series filter is used for low-pass filtering to finally obtain the linearized voltage output.

8. The linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation according to claim 1, characterized in that: Changing the ratio of the voltage divider R1 and R2 not only alters the shape of the exponential carrier but also its frequency. Under the condition of meeting the linearization requirements, increasing the ratio of R1 and R2 can increase the frequency of the exponential carrier, which can reduce the output noise after low-pass filtering.

9. The linearization method for an eddy current displacement sensor based on exponential carrier pulse width modulation according to claim 1, characterized in that: The following preamplifier circuit is used as the eddy current displacement sensor. The preamplifier circuit consists of a signal generator, a probe resonant circuit, a phase-sensitive detector, a micro-signal amplifier, and a bias circuit. The signal generator generates the excitation wave of the eddy current displacement sensor. The voltage waveform obtained by inputting the excitation wave into the probe resonant circuit passes through the phase-sensitive detector, which is composed of an inverter and a high-speed analog switch. After detection, noise with a frequency different from that of the original circuit is filtered out. Then, through the micro-signal amplifier and the bias circuit, the output voltage of the eddy current displacement sensor without linearization is obtained.

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