An absolute inductive displacement sensor and a signal processing method thereof

Abstract

This invention provides an absolute inductive displacement sensor and its signal processing method. The sensor includes a stator and a mover. The stator includes a sensing element and a circuit board. The sensing element has an excitation coil, a first induction coil, and a second induction coil. The two induction coils share the same excitation coil. The circuit board includes: a signal processing module for processing the signals output by the two induction coils; an analog switch for selectively activating one of the channels of the two induction coils; and a main control chip configured to: control the analog switch to select the channel in a time-division multiplexing manner; calculate the first position information based on the signal processing result obtained when the first induction coil channel is activated; calculate the second position information based on the signal processing result obtained when the second induction coil channel is activated; and determine and output the absolute position information based on the first and second position information. This invention solves the problems of circuit complexity and electromagnetic crosstalk that exist in existing absolute sensors using a dual-channel design.

Description

Technical Field

[0001] This invention relates to the field of precision displacement measurement technology, and in particular to an absolute inductive displacement sensor and its signal processing method. Background Technology

[0002] Displacement sensors are key components in modern industrial measurement and control. Their core function is to convert mechanical displacement into measurable electrical or digital signals. Among them, inductive displacement sensors are widely used in harsh industrial environments and aerospace electromechanical systems due to their advantages such as non-contact measurement, resistance to contamination and wear, long lifespan, and insensitivity to strong magnetic fields.

[0003] The basic working principle of an inductive displacement sensor is based on electromagnetic induction. Specifically, a high-frequency current is passed through the excitation coil on the stator to generate an alternating magnetic field, which acts on the metal pattern on the surface of the mover and generates eddy currents and a reverse magnetic field. When the mover rotates or moves linearly, its relative position with the stator induction coil changes, causing the voltage signal output by the induction coil to change. The precise position of the mover can be obtained by calculating this signal.

[0004] Based on the nature of the output signal, displacement sensors are mainly divided into incremental and absolute types. Incremental sensors output periodic pulses and obtain relative displacement by accumulating counts. However, the position information is lost after power failure and there is a risk of cumulative error. In contrast, absolute sensors can directly output a code that uniquely corresponds to each position. The information is not lost after power failure, there is no need to return to zero, and there is no cumulative error. Therefore, absolute sensors have become the main development direction in high-precision fields such as CNC machine tools, robots, and medical devices.

[0005] To achieve absolute measurement, traditional absolute sensors often employ a dual-channel design, meaning they acquire signals through two sets of induction coils (e.g., coarse and fine measurement channels), and then jointly calculate the absolute position. Figure 1 As shown. This design is intended to address the inherent poor fault tolerance of single-track schemes: when using a single-track design, all position information depends on a single track. If the conductor on the track is partially damaged, contaminated, or subjected to strong electromagnetic interference, it will lead to abnormal induction signals, making it impossible to accurately acquire position data and severely affecting the stability and accuracy of the measurement.

[0006] However, the dual-channel design has obvious drawbacks: First, it increases the number of circuit board components and size, which is not conducive to the miniaturization and integration of the sensor; second, the two sets of coils are usually arranged in close space, and the two high-frequency signal processing modules work in parallel, which can easily lead to electromagnetic crosstalk between channels, causing noise from one signal to couple to the other. Especially when the mover is moving at high speed, it will cause signal distortion, interfere with subsequent calculations, and in severe cases, even lead to miscounting or position jumps. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an absolute inductive displacement sensor and its signal processing method. It solves the problems of existing absolute sensors, which, when using a dual-channel design, increase sensor size, hindering miniaturization and integration, and are prone to electromagnetic crosstalk during parallel operation of dual channels, leading to signal distortion and measurement errors.

[0008] According to an embodiment of the present invention, an absolute inductive displacement sensor includes a stator and a mover. The stator includes a sensing plate and a circuit board. The sensing plate is provided with an excitation coil, a first induction coil, and a second induction coil. The first induction coil and the second induction coil share the same excitation coil. The circuit board is provided with:

[0009] The signal processing module is used to process the signals output by the first induction coil and the second induction coil to obtain the corresponding signal processing results;

[0010] An analog switch is used to selectively activate the channel outputs of the first induction coil and the second induction coil;

[0011] The main control chip is configured to: control the analog switch to select the position in a time-division multiplexing manner; calculate the first position information for determining the position interval based on the signal processing result obtained when the first induction coil channel is selected; calculate the second position information for precise correction within the position interval based on the signal processing result obtained when the second induction coil channel is selected; and determine and output the absolute position information based on the first position information and the second position information.

[0012] On the other hand, according to embodiments of the present invention, a signal processing method for an absolute inductive displacement sensor is also provided, the method comprising the following steps:

[0013] Under the control of the main control chip, the channels of the first induction coil and the second induction coil are selected in a time-division manner through analog switches;

[0014] The signal output from the gating channel is processed to obtain the corresponding signal processing result;

[0015] Based on the signal processing results obtained when the first induction coil channel is selected, first position information for determining the position range is calculated; based on the signal processing results obtained when the second induction coil channel is selected, second position information for precise correction within the position range is calculated.

[0016] Based on the first location information and the second location information, the absolute location information is determined and output.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] By introducing the analog switch into the sensor and having the main control chip control the analog switch to perform time-division multiplexing, the output signal of only the first induction coil channel or the second induction coil channel is output at any given time. This completely cuts off the possible direct electrical coupling path between the two induction channels, solves the problem that electromagnetic crosstalk is easily generated in the parallel operation of dual channels of existing absolute sensors, leading to signal distortion and measurement errors, and ensures the purity of signal transmission.

[0019] Although the dual-track design solves the absolute positioning problem, its accompanying dual-parallel processing circuit brings high cost and high power consumption. The absolute inductive displacement sensor of the present invention, by setting the analog switch on the circuit board, fundamentally reduces the types of components, greatly reduces system complexity and power consumption, and improves sensor reliability. Attached Figure Description

[0020] Figure 1 The control principle diagram for an existing absolute sensor using a dual-code channel design.

[0021] Figure 2 This is a control principle diagram of an absolute inductive displacement sensor according to Embodiment 1 of the present invention.

[0022] Figure 3 This is a control principle diagram of an absolute inductive displacement sensor according to Embodiment 1 of the present invention, in which the analog switch is placed at the input of the signal processing module.

[0023] Figure 4 This is a detailed circuit diagram of the signal amplification circuit in Embodiment 2 of the present invention.

[0024] Figure 5 This is a flowchart illustrating the signal output between the analog switch, signal processing module, and main control chip of an absolute inductive displacement sensor according to Embodiment 2 of the present invention.

[0025] Figure 6 This is a detailed circuit diagram of the signal amplification circuit in Embodiment 3 of the present invention.

[0026] Figure 7 This is a flowchart illustrating the signal processing method of an absolute inductive displacement sensor according to Embodiment 4 of the present invention.

[0027] In the above figures: 1. Stator; 2. Mover; 3. Signal processing module; 4. Analog switch; 5. Main control chip; 11. Excitation coil; 12. First induction coil; 13. Second induction coil; 31. Demodulation circuit; 32. Signal amplification circuit; 33. Low-pass filter circuit; 34. Analog-to-digital conversion circuit. Detailed Implementation

[0028] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Example 1

[0030] like Figure 2 As shown, this embodiment of the invention proposes an absolute inductive displacement sensor, including a stator 1 and a mover 2. The stator 1 includes a sensing plate and a circuit board. The sensing plate is provided with an excitation coil 11, a first induction coil 12, and a second induction coil 13. The first induction coil 12 and the second induction coil 13 share the same excitation coil 11. The circuit board is provided with:

[0031] Signal processing module 3 is used to process the signals output by the first induction coil 12 and the second induction coil 13 to obtain corresponding signal processing results;

[0032] Analog switch 4 is used to selectively turn on the channel output of the first induction coil 12 and the second induction coil 13;

[0033] The main control chip 5 is configured to: control the analog switch 4 to select the position in a time-division manner; calculate the first position information for determining the position interval based on the signal processing result obtained when the first induction coil 12 channel is selected; calculate the second position information for precise correction within the position interval based on the signal processing result obtained when the second induction coil 13 channel is selected; and determine and output the absolute position information based on the first position information and the second position information.

[0034] Specifically, although the dual-track design solves the absolute positioning problem, its accompanying dual-parallel processing circuit brings high cost and high power consumption. The absolute inductive displacement sensor of the present invention (the sensing sheet and the circuit board can be integrated or designed separately and soldered together) fundamentally reduces the types of components by setting the analog switch 4 on the circuit board, which greatly reduces the system complexity and power consumption and improves the reliability of the sensor.

[0035] The analog switch 4 has at least one common terminal, and each common terminal has at least two selection terminals, enabling the analog switch 4 to select different induction coils as needed. By introducing the analog switch 4 into the sensor and having the main control chip 5 control the analog switch 4 to perform time-division multiplexing, only one output signal of the first induction coil 12 channel or the second induction coil 13 channel is output at any given time. This completely cuts off any possible direct electrical coupling path between the two induction channels, avoids electromagnetic crosstalk caused by the parallel operation of the two channels, and ensures the purity of signal transmission.

[0036] Preferably, the first induction coil 12 is a coarse pole coil and the second induction coil 13 is a fine pole coil. When the sensor is initially powered on, the coarse pole coil channel is selected to calculate the coarse value of the absolute initial position, and then the fine pole coil channel is selected to calculate the fine value of the absolute position. The absolute position information is calculated by fusing the coarse value of the absolute initial position and the fine value of the absolute position, so that the sensor can achieve absolute positioning with reduced hardware complexity.

[0037] More preferably, the absolute position information of the displacement sensor is calculated using the principle of coprime pole numbers between the outer and inner rings of the sensor. For example, the specific calculation process for the absolute position information is as follows: Assume the first induction coil 12 and the second induction coil 13 are respectively located on the inner and outer rings of the stator 1. The number of poles in the fine measurement section of the outer ring is N, and the number of poles in the coarse measurement section of the inner ring is M, and N and M are coprime. The absolute angular displacement to be measured is... ‎.

[0038] 1. First, calculate the coarse value of the absolute initial position. The steps for calculating the coarse value of the absolute initial position are as follows:

[0039] (1) Obtaining displacement values: Measure the displacement values ​​of the output induced signals of the first induction coil 12 and the second induction coil 13 respectively, and set the displacement value of the first induction coil 12 as... Its value is between 0 and (2 ( / M) periodic variation within the arc range), the displacement value of the second induction coil 13 is set to Its value is between 0 and (2 / N) radians, or equivalent periodic variations within the range of 0 to 360 / N degrees.

[0040] (2) Calculate the difference between the two displacement values: .

[0041] (3) Normalization: If ,but ;like ,but (Since N and M are coprime,) With absolute angular displacement (It has a linear one-to-one mapping relationship over the entire period).

[0042] (4) Determine the coarse value of the absolute initial position: through calculation The number of the current sensor cycle segment (i.e., an integer k) is initially determined. This number of cycle segments corresponds to an angle interval covering the entire cycle, which is the coarse value of the absolute initial position.

[0043] 2. Next, calculate the absolute position precision. The steps for calculating the absolute position precision are as follows: directly extract the subdivision angle value within one pole (i.e., one complete measurement cycle) from the sensor's output signal. , This is the absolute position precision value (range limited to 0 to 360 / N degrees).

[0044] 3. Finally, the absolute position information is obtained through fusion calculation. The steps for calculating the absolute position information are as follows:

[0045] (1) Calculate the number of integer cycles based on the phase difference: The angular displacement to be measured can be directly calculated by measuring the combination of coprime N and M. The largest integer number of cycles contained within the outer ring (precision measurement). The specific formula is as follows:

[0046]

[0047] (2) Calculate the absolute position: Based on the above principle, the absolute angular displacement This can be expressed as the following formula:

[0048]

[0049] in, It is the whole-cycle angle value obtained by combining the results of fine and coarse measurements and the calculation, that is, the coarse value of the absolute initial position; The remaining angle value at high resolution, i.e., the incremental position precision value, is provided by the precision measurement section; the absolute position coarse value is combined with the high-resolution, high-precision precision measurement incremental position value to obtain the accurate absolute position value.

[0050] Furthermore, the signal processing module 3 includes a demodulation circuit 31, a signal amplification circuit 32, a low-pass filter circuit 33, and an analog-to-digital conversion circuit 34 cascaded in sequence, wherein:

[0051] The demodulation circuit 31 is used to demodulate the amplitude of the induced electromotive force in order to extract the induced signal containing position information.

[0052] The signal amplification circuit 32 is used to amplify the amplitude of the induced signal;

[0053] The low-pass filter circuit 33 is used to filter out the high-frequency carrier and environmental noise of the amplified induced signal;

[0054] The analog-to-digital converter circuit 34 is used to convert the filtered analog signal into a digital signal and transmit it to the main control chip 5 for subsequent displacement calculation.

[0055] Specifically, the induction coil of the absolute inductive displacement sensor outputs an AC signal (induced electromotive force) whose amplitude changes with displacement. Its carrier frequency is determined by the excitation coil 11. The induced electromotive force is demodulated by the demodulation circuit 31 to extract a low-frequency or DC signal component proportional to the displacement. Since the demodulated signal is usually very weak, it needs to be amplified to a level suitable for subsequent circuit processing by the signal amplification circuit 32. Then, the low-pass filter circuit 33 filters out the high-frequency carrier component remaining in the demodulated signal and various high-frequency noises from the environment, retaining only the low-frequency effective signal reflecting the displacement change, thereby outputting a smooth and stable DC or low-frequency analog voltage. Finally, the analog-to-digital converter circuit 34 converts the amplified and filtered pure analog voltage signal into digital code for the main control chip 5 to read and process. This systematically solves the problem of converting the original sensor signal into digital position information, ensuring signal integrity, high signal-to-noise ratio, and anti-interference capability.

[0056] Preferably, the low-pass filter circuit 33 is an active low-pass filter circuit 33, which can not only filter out noise more cleanly, but also provide better circuit isolation and driving capability.

[0057] Furthermore, the analog switch 4 is configured to selectively connect to any of the different functional nodes of the signal processing module 3 to change the signal flow path in the signal processing module 3 as needed;

[0058] The different functional nodes of the signal processing module 3 include at least: before the input terminal of the demodulation circuit 31, between the output terminal of the demodulation circuit 31 and the input terminal of the signal amplification circuit 32, between the output terminal of the signal amplification circuit 32 and the input terminal of the low-pass filter circuit 33, between the output terminal of the low-pass filter circuit 33 and the input terminal of the analog-to-digital converter circuit 34, and after the output terminal of the analog-to-digital converter circuit 34.

[0059] Specifically, the analog switch 4 is highly adjustable and can be placed at any node of the signal processing module 3 for flexible deployment according to design objectives.

[0060] Preferably, such as Figure 3As shown, before the analog switch 4 is connected to the input terminal of the demodulation circuit 31, the selected original induction signal is directly sent from the output terminal of the analog switch 4 to the subsequent demodulation circuit 31 through the analog switch 4. This allows the entire subsequent signal processing link (demodulation, amplification, filtering, analog-to-digital conversion) to be completely shared by the two induction signals. The systematic gain error, offset error, or phase error introduced by the signal link will exist in the two signals in the same proportion or magnitude. After signal processing, when the processing results are fused, the systematic gain error, offset error, or phase error will be naturally differentially canceled or eliminated as a common reference, thereby eliminating the systematic errors caused by parameters and drift in the dual-channel design.

[0061] Meanwhile, since the analog switch 4 is placed at the very beginning of the processing link, although it processes weak raw signals, the output impedance of the induction coil is usually high. At this time, as long as the on-resistance (Ron) of the analog switch 4 is within a reasonable range (e.g., tens of ohms), the voltage division effect it generates has little impact on the demodulation circuit 31 with high input impedance. Therefore, the performance requirements of the analog switch 4 are relatively relaxed.

[0062] The detailed working process of this embodiment is as follows:

[0063] The main control chip 5 generates a high-frequency excitation signal and applies it to the excitation coil 11 of the stator 1, causing the excitation coil 11 to generate an alternating magnetic field. This magnetic field acts on the metal pattern on the surface of the mover 2, generating an alternating magnetic field in the opposite direction (the stator 1 and the mover 2 remain parallel with a small gap). When the mover 2 rotates or undergoes linear displacement, the relative position between the metal pattern on the surface of the mover 2 and the first induction coil 12 or the second induction coil 13 of the stator 1 changes. This change directly affects the induced electromotive force picked up by the first induction coil 12 or the second induction coil 13, ultimately causing corresponding changes in the voltage signals (i.e., coarse and fine pole signals) output by the first induction coil 12 or the second induction coil 13. Afterwards, the main control chip 5 controls the analog switch 4 to... Upon initial power-on, the first induction coil 12 channel is selected, causing the coarse polarity signal output by the first induction coil 12 to be transmitted to the signal processing module 3 for demodulation, amplification, filtering, and analog-to-digital conversion processing to obtain a first signal processing result. Then, based on the first signal processing result, an absolute initial position coarse value for determining the position range is calculated. Subsequently, the main control chip 5 controls the analog switch 4 to select the second induction coil 13 channel, causing the fine polarity signal output by the second induction coil 13 to be transmitted to the signal processing module 3 for demodulation, amplification, filtering, and analog-to-digital conversion processing to obtain a second signal processing result. Then, based on the second signal processing result, an absolute position fine value for precise correction within the position range is calculated. Finally, the absolute initial position coarse value and the absolute position fine value are combined to calculate the absolute position information, thus realizing absolute position measurement.

[0064] Example 2

[0065] like Figure 4 and Figure 5 As shown, based on Embodiment 1, the signal amplification circuit 32 proposed in this embodiment of the invention includes a first amplification unit and a second amplification unit;

[0066] The inverting input terminal of the second amplification unit is coupled to the inverting input terminal of the first amplification unit through an impedance network, so that the first amplification unit and the second amplification unit work together to form a differential amplification architecture for suppressing common-mode interference and amplifying differential-mode signals.

[0067] In this embodiment, as Figure 4As shown, the non-inverting input terminal of the first amplification unit receives a first input signal, and the non-inverting input terminal of the second amplification unit receives a second input signal. The second input signal and the first input signal are two inverted signals. The output terminal of the first amplification unit outputs a first output signal and is connected to the inverting input terminal of the first amplification unit through a resistor R1. The output terminal of the second amplification unit outputs a second output signal and is connected to the inverting input terminal of the second amplification unit through a resistor R3. The inverting input terminal of the second amplification unit is coupled to the inverting input terminal of the first amplification unit through a resistor R2, so that the signal amplification circuit 32 achieves the purpose of amplifying differential-mode signals and suppressing common-mode signals.

[0068] Example 3

[0069] like Figure 6 As shown, based on Embodiment 1, the signal amplification circuit 32 proposed in this embodiment of the invention includes a first amplification unit, a second amplification unit, and a gain selection unit;

[0070] The gain selection unit has a common terminal and at least two selection terminals to switch between different gain configurations;

[0071] The inverting input terminal of the first amplification unit is connected to its output terminal through a first feedback network, and the inverting input terminal of the second amplification unit is connected to its output terminal through a second feedback network. The inverting input terminal of the first amplification unit is selectively connected to the inverting input terminal of the second amplification unit through the gain selection unit, so that the overall gain of the signal amplification circuit 32 can be changed according to the switching state of the gain selection unit.

[0072] In this embodiment, as Figure 6 As shown, the non-inverting input of the first amplification unit receives a first input signal, and the non-inverting input of the second amplification unit receives a second input signal. The second input signal and the first input signal are two inverted signals. The output of the first amplification unit outputs a first output signal and is connected to the inverting input of the first amplification unit through a resistor R1. The output of the second amplification unit outputs a second output signal and is connected to the inverting input of the second amplification unit through a resistor R3. The inverting input of the first amplification unit is selectively connected to the inverting input of the second amplification unit through the gain selection unit. The gain selection unit has one common terminal and two selection terminals. The common terminal is connected to the inverting input of the second amplification unit, and the two selection terminals are connected to the inverting input of the first amplification unit through resistors R2 and R4, respectively. This allows for gain adjustment while maintaining a high common-mode rejection ratio (CMRR), ensuring that the amplitudes of coarse and fine measurements remain consistent.

[0073] Example 4

[0074] On the other hand, such as Figure 7 As shown in the figure, this embodiment of the invention also provides a signal processing method for an absolute inductive displacement sensor, the method comprising the following steps:

[0075] S1. Under the control of the main control chip 5, the channels of the first induction coil 12 and the second induction coil 13 are selected and output through the analog switch 4 in a time-division manner;

[0076] S2. Process the signal output from the gating channel to obtain the corresponding signal processing result;

[0077] S3. Based on the signal processing results obtained when the first induction coil 12 channel is selected, the first position information for determining the position interval is calculated; based on the signal processing results obtained when the second induction coil 13 channel is selected, the second position information for precise correction within the position interval is calculated.

[0078] S4. Based on the first location information and the second location information, determine and output the absolute location information.

[0079] In this embodiment, the coarse pole signal generated and output by the first induction coil 12 and the fine pole signal generated and output by the second induction coil 13 are demodulated, amplified, filtered and converted from analog to digital in sequence to obtain the first signal processing result and the second signal processing result, respectively. Then, the coarse value of the absolute initial position used to determine the position interval is calculated based on the first signal processing result. The fine value of the absolute position used to make precise correction within the position interval is calculated based on the second signal processing result. Finally, the absolute position information is calculated by combining the coarse value of the absolute initial position and the fine value of the absolute position, that is, the absolute position measurement is realized.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An absolute inductive displacement sensor, comprising a stator and a mover, characterized in that, The stator includes a sensing plate and a circuit board. The sensing plate is provided with an excitation coil, a first induction coil, and a second induction coil. The first induction coil and the second induction coil share the same excitation coil. The circuit board is provided with: The signal processing module is used to process the signals output by the first induction coil and the second induction coil to obtain the corresponding signal processing results; An analog switch is used to selectively activate the channel outputs of the first induction coil and the second induction coil; The main control chip is configured to: control the analog switch to select the position in a time-division multiplexing manner; and calculate the first position information for determining the position range based on the signal processing result obtained when the first induction coil channel is selected. Based on the signal processing results obtained when the second induction coil channel is selected, second position information for precise correction within the position range is calculated; based on the first position information and the second position information, absolute position information is determined and output.

2. The absolute inductive displacement sensor as described in claim 1, characterized in that, The signal processing module includes a demodulation circuit, a signal amplification circuit, a low-pass filter circuit, and an analog-to-digital converter circuit cascaded in sequence, wherein: The demodulation circuit is used to demodulate the amplitude of the induced electromotive force in order to extract the induced signal containing position information. The signal amplification circuit is used to amplify the amplitude of the induced signal; The low-pass filter circuit is used to filter out the high-frequency carrier wave and environmental noise of the amplified induced signal; The analog-to-digital converter circuit is used to convert the filtered analog signal into a digital signal and transmit it to the main control chip for subsequent displacement calculation.

3. An absolute inductive displacement sensor as described in claim 2, characterized in that, The analog switch is configured to be selectively connected to any of the different functional nodes of the signal processing module to change the signal flow path in the signal processing module as needed. The different functional nodes of the signal processing module include at least: before the input terminal of the demodulation circuit, between the output terminal of the demodulation circuit and the input terminal of the signal amplification circuit, between the output terminal of the signal amplification circuit and the input terminal of the low-pass filter circuit, between the output terminal of the low-pass filter circuit and the input terminal of the analog-to-digital conversion circuit, and after the output terminal of the analog-to-digital conversion circuit.

4. An absolute inductive displacement sensor as described in claim 3, characterized in that, The analog switch is connected before the input terminal of the demodulation circuit.

5. An absolute inductive displacement sensor as described in claim 2, characterized in that, The signal amplification circuit includes a first amplification unit and a second amplification unit; The inverting input terminal of the second amplification unit is coupled to the inverting input terminal of the first amplification unit through an impedance network, so that the first amplification unit and the second amplification unit work together to form a differential amplification architecture for suppressing common-mode interference and amplifying differential-mode signals.

6. An absolute inductive displacement sensor as described in claim 2, characterized in that, The signal amplification circuit includes a first amplification unit, a second amplification unit, and a gain selection unit; The gain selection unit has a common terminal and at least two selection terminals to switch between different gain configurations; The inverting input terminal of the first amplification unit is connected to its output terminal through a first feedback network, and the inverting input terminal of the second amplification unit is connected to its output terminal through a second feedback network. The inverting input terminal of the first amplification unit is selectively connected to the inverting input terminal of the second amplification unit through the gain selection unit, so that the overall gain of the signal amplification circuit can be changed according to the switching state of the gain selection unit.

7. An absolute inductive displacement sensor as described in claim 2, characterized in that, The low-pass filter circuit is an active low-pass filter circuit.

8. A signal processing method for an absolute inductive displacement sensor, applied to an absolute inductive displacement sensor according to any one of claims 1-7, characterized in that, The method includes the following steps: Under the control of the main control chip, the channels of the first induction coil and the second induction coil are selected in a time-division manner through analog switches; The signal output from the gating channel is processed to obtain the corresponding signal processing result; Based on the signal processing results obtained when the first induction coil channel is selected, first position information for determining the position range is calculated; based on the signal processing results obtained when the second induction coil channel is selected, second position information for precise correction within the position range is calculated. Based on the first location information and the second location information, the absolute location information is determined and output.

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