Digital eddy current sensor detection circuit and signal decoupling method

Abstract

This invention discloses a digital eddy current sensor detection circuit and signal decoupling method, relating to the field of micro-nano detection technology, and can be used to measure parameters such as the thickness of micro-nano metal thin films or minute gaps. The circuit includes a digital-to-analog conversion module, a signal conversion module, a front-end signal conditioning module, an analog-to-digital conversion module, and a digital signal processing module. This invention can generate excitation signals of different frequencies and amplitudes and can simultaneously process input signals of different frequencies, facilitating the adjustment and control of the excitation signal. Furthermore, this invention utilizes digital signals to improve the sensor's anti-interference capability, which is beneficial for extracting minute signals.

Description

Technical Field

[0001] This invention relates to the field of micro-nano detection technology, specifically to a digital eddy current sensor detection circuit and signal decoupling method. Background Technology

[0002] For measurements requiring nanoscale metal thin film thickness and micrometer-level displacement, eddy current sensors suffer from minute changes in their internal characteristic signals. Furthermore, in practical engineering applications, they are susceptible to external interference, such as ambient temperature and noise, which negatively impacts the stability of high-precision measurements. Designing a digital eddy current sensor significantly improves its anti-interference capabilities and enhances the operability of frequency control, avoiding the hardware limitations of adjusting the excitation frequency using conventional analog circuits, thereby reducing costs. Additionally, designing a decoupling module for the detection circuit can suppress the influence of ambient temperature variations on the output signal, improving sensor detection accuracy. Summary of the Invention

[0003] In view of this, the present invention provides a digital eddy current sensor circuit and signal decoupling method, which can generate excitation signals of different frequencies and process input signals of different frequencies by modifying the internal reference signal lookup table, thereby achieving frequency conversion detection and obtaining more effective detection information.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: a digital eddy current sensor detection circuit, including a digital-to-analog conversion module, a signal conversion module, a front-end signal conditioning module, an analog-to-digital conversion module, and a digital signal processing module.

[0005] The digital-to-analog conversion module is controlled by the DAC control module in the digital signal processing module. It is responsible for converting digital signals into analog signals and generating stable sinusoidal excitation signals. The sinusoidal excitation signals are filtered and amplified before being applied to the signal conversion module to excite the detection coil therein. At the same time, the amplitude and frequency of the output sinusoidal excitation signal are controlled by the DAC control module inside the digital signal processing module, which can realize the generation of sinusoidal excitation signals with different amplitudes and frequencies.

[0006] The signal conversion module uses an LC parallel resonant circuit or an AC bridge circuit to convert the impedance change of the detection coil into a voltage signal for output; the detection coil in the LC parallel resonant circuit and the AC bridge circuit is the sensitive element in the digital eddy current sensor.

[0007] The front-end signal conditioning module uses a fully differential operational amplifier. The output voltage signal of the signal conversion module serves as the input of the front-end signal conditioning module, amplifying the input signal while matching the interface voltage range and interface type of the analog-to-digital conversion module. The output of the front-end signal conditioning module is an analog signal.

[0008] The analog-to-digital converter module converts the analog signal output from the front-end signal conditioning module into a digital signal and outputs it to the digital signal processing module.

[0009] The digital signal processing module uses a field-programmable gate array (FPGA). This digital signal processing module includes a DAC control module and a decoupling module. The DAC control module is used to control the amplitude and frequency of the sinusoidal excitation signal output by the digital-to-analog converter module. The digital decoupling module is used to decouple the input digital signal, calculate the measurement results of the eddy current sensor, and output them.

[0010] Furthermore, the signal conversion module employs an LC parallel resonant circuit or an AC bridge circuit to convert the impedance change of the detection coil into a voltage signal for output, specifically:

[0011] If the signal conversion module uses an LC parallel resonant circuit, the LC parallel resonant circuit includes a series voltage divider resistor, a parallel capacitor, and a detection coil; the signal conversion module converts the impedance change of the detection coil into a corresponding output voltage signal; wherein the resistance of the series voltage divider resistor is Rp, and the capacitance of the parallel capacitor is C = 1 / 4π 2 f 2 L, where L is the initial inductance of the detection coil; f is the frequency of the sinusoidal excitation signal; the parallel capacitor is connected in parallel with the detection coil, and the voltage between the intersection points a and b is the output signal of the signal conversion module, which reflects the impedance change of the detection coil.

[0012] If the signal conversion module uses an AC bridge circuit, the AC bridge circuit includes a reference coil, a detection coil, and two sampling resistors with a resistance value of Rs. The AC bridge circuit consists of four arms connected together, with the reference coil, detection coil, and two sampling resistors each occupying one arm. The reference coil and detection coil are adjacent, and the two sampling resistors are adjacent. The intersection point between the reference coil and its adjacent sampling resistor is d, and the intersection point between the detection coil and its adjacent sampling resistor is h. The voltage between intersection points d and h is the output signal of the signal conversion module, which reflects the impedance change of the detection coil.

[0013] Furthermore, the conversion process of the analog-to-digital converter is as follows: the output signal of the front-end signal conditioning module is x(t) = Asin(2πft + ψ), which becomes x(n) = Asin(2πn / N + ψ) after passing through the digital-to-analog converter, where n represents the discrete point sequence after conditioning, n = 0, 1…N-1, A is the signal amplitude, ψ is the phase, and N = f s / f, fs represents the sampling frequency of the analog-to-digital converter module, and N represents the number of sampling points in each cycle.

[0014] Furthermore, the decoupling module includes two reference signal lookup tables, a first digital multiplier, a second digital multiplier, a first digital filter, a second digital filter, and a communication output module.

[0015] Two reference signal lookup tables, namely the sine reference signal lookup table and the cosine reference signal lookup table, are used to achieve an accurate 90° phase shift. At the same time, by modifying the two reference signal lookup tables, input signals of different frequencies can be processed.

[0016] The first digital multiplier is used to perform digital multiplication of the input digital signal and the sinusoidal reference signal, and the output of the first digital multiplier is sent to the first digital filter.

[0017] The second digital multiplier is used to perform digital multiplication on the input digital signal and the cosine reference signal, and the output of the second digital multiplier is sent to the second digital filter.

[0018] The first digital filter and the second digital filter have the same structure, and the outputs of both the first digital filter and the second digital filter are sent to the output module for output.

[0019] The output module is responsible for outputting two DC signals to calculate the measured quantity.

[0020] Another embodiment of the present invention provides a signal decoupling method for a digital eddy current sensor detection circuit, comprising the following steps:

[0021] Step 1: Use the digital-to-analog converter module to generate a stable sinusoidal excitation signal, filter and amplify it, and use it as the excitation signal for the LC parallel resonant circuit or AC bridge circuit to act on the detection coil.

[0022] Step 2: The LC parallel resonant circuit or AC bridge circuit converts the impedance change of the detection coil into a voltage signal for output; the detection coil in the LC parallel resonant circuit and AC bridge circuit is the sensitive element in the digital eddy current sensor.

[0023] Step 3: Use a fully differential operational amplifier to process the voltage signal output from the LC parallel resonant circuit or AC bridge circuit, and output an analog signal.

[0024] Step 4: Use an analog-to-digital converter to convert the analog signal output from the fully differential operational amplifier into a digital signal.

[0025] Step 5: Decouple the digital signal output by the analog-to-digital converter module, calculate and output the measurement results of the eddy current sensor.

[0026] Furthermore, step four includes the following specific processes:

[0027] The output signal of the front-end signal conditioning module is x(t)=Asin(2πft+ψ), which becomes x(n)=Asin(2πn / N+ψ) after passing through the digital-to-analog converter module. Here, n represents the conditioned point sequence, n=0,1…N-1, A is the signal amplitude, ψ is the phase, N=fs / f, fs represents the sampling frequency of the analog-to-digital converter module, f is the excitation signal frequency, and N represents the number of sampling points in each cycle.

[0028] Furthermore, step five includes the following specific steps:

[0029] Step 501: Set up two reference signal lookup tables, namely a sine reference signal lookup table and a cosine reference signal lookup table, to realize sine and cosine reference signals with the same frequency and a 90° phase difference. By modifying the two reference signal lookup tables, input signals of different frequencies can be processed.

[0030] Step 502: Perform digital multiplication operations on the input digital signal with the sine reference signal and the cosine reference signal respectively, and send the results of the two digital multiplication operations into the digital filter.

[0031] Step 503: The digital filter filters the results of the two digital multiplication operations to obtain the DC components of each path, and sends them to the output module for output calculation and calculation of the measurement results of the eddy current sensor.

[0032] Further, step 502 specifically includes:

[0033] r1(n)=Asin(2πn / N+ψ)·Bsin(2πn / N)

[0034] =-0.5AB[cos(4πn / N+ψ)-cos(ψ)]

[0035] r2(n)=Asin(2πn / N+ψ)·Bcos(2πn / N)

[0036] =0.5AB[sin(4πn / N+ψ)+sin(ψ)]

[0037] Where r1(n) and r2(n) are the results of two digital multiplication operations; Bsin(2πn / N) is the sine reference signal; Bcos(2πn / N) is the cosine reference signal; and B is the amplitude of the reference signal.

[0038] Furthermore, the two DC components in step 503 are respectively: r 10 (n) = 0.5ABcos(ψ), r 20 (n) = 0.5ABsin(ψ), from r 10 r 20 It can calculate the measurement results of the eddy current sensor.

[0039] Beneficial effects:

[0040] 1. This invention provides a digital eddy current sensor circuit and signal decoupling method, which can generate and process excitation signals of different frequencies to achieve frequency conversion detection and obtain more effective detection information. This invention is geared towards micro-nano detection, providing a digital detection circuit design method and detection algorithm design, which can extract minute signals under significant external interference and has the ability to process input signals of different frequencies.

[0041] 2. This invention can improve the detection accuracy and anti-interference capability of eddy current sensors, meet the needs of micro-nano detection, realize frequency conversion detection, and improve system reliability and flexibility. Attached Figure Description

[0042] Figure 1 This is a block diagram of the digital eddy current sensor detection circuit provided in an embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of a digital eddy current sensor signal conversion circuit provided in an embodiment of the present invention;

[0044] Figure 3 This is a flowchart illustrating the decoupling module in the digital signal processing module of the digital eddy current sensor provided in an embodiment of the present invention. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] This invention provides a digital eddy current sensor detection circuit and its digital signal processing algorithm. Figure 1 The block diagram of the digital eddy current sensor detection circuit provided in the embodiment of the present invention is shown. The detection circuit includes a digital-to-analog conversion module, a signal conversion module, an analog-to-digital conversion module, a front-end signal conditioning module, and a digital signal processing module.

[0047] The digital-to-analog conversion module is controlled by the DAC control module in the digital signal processing module. It is responsible for converting digital signals into analog signals and generating stable sinusoidal excitation signals. The sinusoidal excitation signals are filtered, amplified, and then applied to the signal conversion module to excite the detection coil. At the same time, the amplitude and frequency of the output sinusoidal excitation signal are controlled by the DAC control module inside the digital signal processing module, which can realize the generation of sinusoidal excitation signals with different amplitudes and frequencies.

[0048] The signal conversion module can employ an LC parallel resonant circuit or an AC bridge circuit to convert the impedance change of the sensitive element into a voltage signal for output. The detection coil in the LC parallel resonant circuit and the AC bridge circuit is the sensitive element in a digital eddy current sensor. In this embodiment of the invention, the LC parallel resonant circuit includes a series voltage divider resistor 1, a parallel capacitor 2, and a detection coil 3, as shown below. Figure 2 As shown. The value C of the parallel capacitor is selected based on the inductance of the detection coil and the frequency of the excitation signal; C = 1 / 4π 2 f 2 L, where f is the excitation signal frequency and L is the initial inductance of the detection coil. This module converts the change in impedance information of the detection coil into a change in voltage. The detection coil is connected in parallel with a parallel capacitor, and the voltage between the intersection points a and b is the output signal of the signal conversion module. In another embodiment of the present invention, the AC bridge circuit consists of a reference coil 4, a detection coil 5, and two sampling resistors 6 (with a resistance value of Rs). The AC bridge circuit is composed of four bridge arms connected together, with the reference coil 4, the detection coil 5, and the two sampling resistors 6 each located on one bridge arm. The reference coil 4 and the detection coil 5 are adjacent, and the two sampling resistors 6 are adjacent. The intersection point between the reference coil 4 and its adjacent sampling resistor 6 is d, and the intersection point between the detection coil 5 and its adjacent sampling resistor 6 is h. The voltage between intersection points d and h is the output signal of the signal conversion module, which reflects the amount of impedance change of the detection coil.

[0049] The front-end signal conditioning module uses a fully differential operational amplifier. The output voltage signal of the signal conversion module serves as the input of the front-end signal conditioning module, amplifying the input signal while matching the interface voltage range and interface type of the analog-to-digital conversion module. The output of the front-end signal conditioning module is an analog signal.

[0050] The analog-to-digital converter (ADC) converts the analog signal output from the front-end signal conditioning module into a digital signal, which is then sent to the digital signal processing module. In this embodiment of the invention, the output signal of the front-end signal conditioning module is x(t) = Asin(2πft + ψ), which becomes x(n) = Asin(2πn / N + ψ) after high-speed ADC conversion, where n represents the conditioned point sequence, n = 0, 1…N-1, A is the signal amplitude, ψ is the phase, N = fs / f, fs represents the sampling frequency, and N represents the number of sampling points in each cycle.

[0051] The digital signal processing module employs a Field-Programmable Gate Array (FPGA). This module includes a DAC control module and a decoupling module. The DAC control module controls the amplitude and frequency of the sinusoidal excitation signal from the digital-to-analog converter (DAC). Simultaneously, the decoupling module decouples the input digital signal to obtain and output the measurement results from the eddy current sensor. In this embodiment, the digital signal processing module uses an FPGA and includes a DAC control module and a decoupling module. The decoupling module includes two reference signal lookup tables, two digital multipliers, two digital filters, and an output module, as shown below. Figure 3 As shown in the diagram. This module processes the digital signal output from the analog-to-digital converter to obtain a DC signal containing coil impedance information. The specific implementation process is as follows: First, sine and cosine reference signal lookup tables are generated to obtain sine and cosine reference signals with the same frequency but a 90° phase difference. By modifying the two reference signal lookup tables, input signals of different frequencies can be processed. Then, the digital signal to be measured is multiplied digitally with the sine and cosine reference signals, and then enters the digital filtering module. After filtering out the AC signal, the digital filtering module obtains the DC components containing coil impedance information for each path. The calculation process of the digital signal processing module is as follows:

[0052] First, multiply the signal to be measured by the reference signal, and output two digital signals:

[0053] r1(n)=Asin(2πn / N+ψ)·Bsin(2πn / N)=-0.5AB[cos(4πn / N+ψ)-cos(ψ)]

[0054] r2(n)=Asin(2πn / N+ψ)·Bcos(2πn / N)=0.5AB[sin(4πn / N+ψ)+sin(ψ)]

[0055] After passing through two digital filtering modules, two DC components are obtained:

[0056] r 10 (n) = 0.5ABcos(ψ), r 20 (n) = 0.5ABsin(ψ)

[0057] The output module transmits two DC digital signals to the host computer, which is then controlled by r. 10 r 20 It can calculate the measured value.

[0058] A signal decoupling method for a digital eddy current sensor detection circuit, characterized by comprising the following steps:

[0059] Step 1: Use the digital-to-analog converter module to generate a stable sinusoidal excitation signal, and after filtering and amplification, use it as the excitation signal for the LC parallel resonant circuit or AC bridge circuit;

[0060] Step 2: The LC parallel resonant circuit or AC bridge circuit converts the impedance change of the detection coil into a voltage signal for output; the detection coil in the LC parallel resonant circuit and AC bridge circuit is the sensitive element in the eddy current sensor.

[0061] Step 3: Use a fully differential operational amplifier to process the output voltage signal of the LC parallel resonant circuit or AC bridge circuit, and output an analog signal;

[0062] Step 4: The analog signal output by the fully differential operational amplifier is converted into a digital signal using an analog-to-digital converter (ADC). In this embodiment, the output signal of the front-end signal conditioning module is x(t) = Asin(2πft + ψ), which is converted into x(n) = Asin(2πn / N + ψ) after passing through the ADC, where n represents the conditioned point sequence, n = 0, 1…N-1, A is the signal amplitude, ψ is the phase, and N = f s / f, f s The sampling frequency of the analog-to-digital converter module is represented by f, where f is the excitation signal frequency, and N represents the number of sampling points in each cycle.

[0063] Step 5: Decouple the digital signal to obtain and output the measurement results from the eddy current sensor. In this embodiment of the invention, step 5 includes the following specific steps:

[0064] Step 501: Set up two reference signal lookup tables, namely a sine reference signal lookup table and a cosine reference signal lookup table, to realize sine reference signals and cosine reference signals with the same frequency and a 90° phase difference. Process input signals of different frequencies by modifying the two reference signal lookup tables.

[0065] Step 502: Perform digital multiplication operations on the input digital signal with the sine reference signal and the cosine reference signal respectively, and send the results of both digital multiplication operations to the digital filter; in this embodiment of the invention, the specific results of the two digital multiplication operations are as follows:

[0066] r1(n)=Asin(2πn / N+ψ)·Bsin(2πn / N)

[0067] =-0.5AB[cos(4πn / N+ψ)-cos(ψ)]

[0068] r2(n)=Asin(2πn / N+ψ)·Bcos(2πn / N)

[0069] =0.5AB[sin(4πn / N+ψ)+sin(ψ)]

[0070] Where r1(n) and r2(n) are the results of two digital multiplication operations; Bsin(2πn / N) is the sine reference signal; Bcos(2πn / N) is the cosine reference signal; and B is the amplitude of the reference signal.

[0071] Step 503: The digital filter filters the results of the two digital multiplication operations respectively, and the DC component results of each path are sent to the output module for output. In this embodiment of the invention, the two DC components are: r 10 (n)=0.5Acos(ψ), r 20 (n) = 0.5Asin(ψ). From r 10 r 20 It can calculate the measured value.

[0072] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A digital eddy current sensor detection circuit, characterized in that, The detection circuit includes a digital-to-analog conversion module, a signal conversion module, a front-end signal conditioning module, an analog-to-digital conversion module, and a digital signal processing module; The digital-to-analog conversion module converts digital signals into analog signals. The DAC control module in the digital signal processing module controls the generation of a stable sinusoidal excitation signal. The sinusoidal excitation signal is filtered, amplified, and then applied to the signal conversion module to excite the detection coil therein. At the same time, the DAC control module inside the digital signal processing module controls the amplitude and frequency of the output sinusoidal excitation signal to generate sinusoidal excitation signals with different amplitudes and frequencies. The signal conversion module uses an LC parallel resonant circuit or an AC bridge circuit to convert the impedance change of the detection coil into a voltage signal for output; the detection coil in the LC parallel resonant circuit and the AC bridge circuit is the sensitive element in the digital eddy current sensor. The front-end signal conditioning module uses a fully differential operational amplifier. The output voltage signal of the signal conversion module is used as the input of the front-end signal conditioning module. While amplifying the input signal, it matches the interface voltage range and interface type of the analog-to-digital conversion module. The output of the front-end signal conditioning module is an analog signal. The analog-to-digital conversion module converts the analog signal output from the front-end signal conditioning module into a digital signal and outputs it to the digital signal processing module. The digital signal processing module employs a field-programmable gate array (FPGA). This module includes a DAC control module and a decoupling module. The DAC control module controls the amplitude and frequency of the sinusoidal excitation signal of the digital-to-analog converter. The decoupling module decouples the input digital signal, calculates the measurement results of the eddy current sensor, and outputs them.

2. The digital eddy current sensor detection circuit as described in claim 1, characterized in that, The signal conversion module employs an LC parallel resonant circuit or an AC bridge circuit to convert the impedance change of the detection coil into a voltage signal for output. Specifically: If the signal conversion module adopts an LC parallel resonant circuit, the LC parallel resonant circuit includes a series voltage divider resistor (1), a parallel capacitor (2), and a detection coil (3); wherein the resistance of the series voltage divider resistor is Rp, and the capacitance of the parallel capacitor is C = 1 / 4π. 2 f 2 L, where L is the initial inductance value of the detection coil; f is the frequency of the sinusoidal excitation signal; the parallel capacitor (2) is connected in parallel with the detection coil (3), and the voltage between the intersection points a and b is the output signal of the signal conversion module, which reflects the impedance change of the detection coil; If the signal conversion module adopts an AC bridge circuit, the AC bridge circuit includes a reference coil (4), a detection coil (5) and two sampling resistors (6). The resistance value of the sampling resistor is Rs. The AC bridge circuit is composed of four bridge arms connected together. The reference coil (4), the detection coil (5) and the two sampling resistors (6) are each on one bridge arm. The reference coil (4) and the detection coil (5) are adjacent, and the two sampling resistors (6) are adjacent. The intersection point between the reference coil (4) and its adjacent sampling resistor (6) is d, and the intersection point between the detection coil (5) and its adjacent sampling resistor (6) is h. The voltage between the intersection point d and h is the output signal of the signal conversion module, which reflects the impedance change of the detection coil.

3. The digital eddy current sensor detection circuit as described in claim 1, characterized in that, The conversion process of the analog-to-digital conversion module is as follows: The output signal of the front-end signal conditioning module is x(t) = Asin(2πft + ψ), which becomes x(n) = Asin(2πn / N + ψ) after passing through the digital-to-analog converter module, where n represents the discrete point sequence after conditioning, n = 0, 1, ..., N-1, A is the signal amplitude, ψ is the phase, and N = f s / f, f s This represents the sampling frequency of the analog-to-digital conversion module, and N represents the number of sampling points in each cycle.

4. The digital eddy current sensor detection circuit as described in claim 1, characterized in that, The decoupling module includes two reference signal lookup tables, a first digital multiplier, a second digital multiplier, a first digital filter, a second digital filter, and an output module; The two reference signal lookup tables, namely the sine reference signal lookup table and the cosine reference signal lookup table, are used to achieve an accurate 90° phase shift. By modifying the two reference signal lookup tables, input signals of different frequencies can be processed. The first digital multiplier is used to perform digital multiplication on the input digital signal and the sinusoidal reference signal, and the output of the first digital multiplier is the input of the first digital filter; The second digital multiplier is used to perform digital multiplication on the input digital signal and the cosine reference signal, and the output of the second digital multiplier is the input of the second digital filter; The first digital filter and the second digital filter have the same structure. The outputs of the first digital filter and the second digital filter are both sent to the output module for output, filtering out AC signals and obtaining DC components. The output module is responsible for outputting two DC signals to calculate the measurement results of the eddy current sensor.

5. A signal decoupling method for a digital eddy current sensor detection circuit, characterized in that, Includes the following steps: Step 1: Use the digital-to-analog converter module to generate a stable sinusoidal excitation signal, and after filtering and amplification, use it as the excitation signal for the LC parallel resonant circuit or AC bridge circuit; Step 2: The LC parallel resonant circuit or AC bridge circuit converts the impedance change of the detection coil into a voltage signal for output; the detection coil in the LC parallel resonant circuit and AC bridge circuit is the sensitive element of the eddy current sensor. Step 3: Use a fully differential operational amplifier to process the voltage signal output from the LC parallel resonant circuit or AC bridge circuit, and output an analog signal; Step 4: Use an analog-to-digital converter to convert the analog signal output by the fully differential operational amplifier into a digital signal; Step 5: Decouple the digital signal output by the analog-to-digital converter module, calculate and output the measurement result of the eddy current sensor.

6. The signal decoupling method for the digital eddy current sensor detection circuit as described in claim 5, characterized in that, Step four includes the following specific process: The output signal of the front-end signal conditioning module is x(t) = Asin(2πft + ψ), which, after passing through the analog-to-digital converter module, becomes x(n) = Asin(2πn / N + ψ), where n represents the discrete point order, n = 0, 1, ..., N-1, A is the signal amplitude, ψ is the phase, and N = f s / f, f s The sampling frequency of the analog-to-digital converter module is represented by f, where f is the excitation signal frequency, and N represents the number of sampling points in each cycle.

7. The signal decoupling method for the digital eddy current sensor detection circuit as described in claim 6, characterized in that, Step five includes the following specific steps: Step 501: Set up two reference signal lookup tables, namely a sine reference signal lookup table and a cosine reference signal lookup table, so that two reference signals with the same amplitude and frequency but a phase difference of 90° can process input signals of different frequencies by modifying the two reference signal lookup tables; Step 502: Perform digital multiplication operations on the input digital signal with the generated sine reference signal and cosine reference signal respectively, and then send the results of the two digital multiplication operations into the digital filter; Step 503: The digital filter filters the results of the two digital multiplication operations respectively to obtain the DC components of each path, and sends them to the output module for output and calculation of the measurement results of the eddy current sensor.

8. The signal decoupling method for the digital eddy current sensor detection circuit as described in claim 7, characterized in that, Step 502 specifically includes: r1(n)=Asin(2πn / N+ψ)·Bsin(2πn / N) =-0.5AB[cos(4πn / N+ψ)-cos(ψ)] r2(n)=Asin(2πn / N+ψ)·Bcos(2πn / N) =0.5AB[sin(4πn / N+ψ)+sin(ψ)] Where r1(n) and r2(n) are the results of two digital multiplication operations; Bsin(2πn / N) is the sine reference signal; Bcos(2πn / N) is the cosine reference signal; and B is the amplitude of the reference signal.

9. The signal decoupling method for a digital eddy current sensor detection circuit as described in claim 8, characterized in that, The two DC components in step 503 are: r 10 (n) = 0.5ABcos(ψ), r 20 (n) = 0.5ABsin(ψ), from r 10 r 20 Calculate the measurement results of the eddy current sensor.

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