Dual-parameter synchronous sensing eddy current sensor detection circuit and method

Abstract

The application discloses an eddy current sensor detection circuit and method for realizing double-parameter synchronous sensing, and provides a signal processing algorithm and a detection circuit for an eddy current sensor device, so that synchronous and rapid detection of double physical quantities, i.e., micron-level displacement-temperature or nanometer-level metal film thickness-temperature, can be realized. The detection circuit specifically comprises: an excitation module which provides a stable sinusoidal excitation signal for a signal conversion module and a characteristic component decoupling module. The signal conversion module converts an impedance change of a sensitive element of the eddy current sensor into a detection voltage signal under the action of the sinusoidal excitation signal and outputs the detection voltage signal. The characteristic component decoupling module decouples the output signal of the signal conversion module and amplifies and outputs the output signal through an output module. Meanwhile, a signal processing algorithm is further provided based on the detection circuit.

Description

Technical Field

[0001] This invention relates to the field of micro-nano detection technology, specifically to an eddy current sensor detection circuit and method for realizing simultaneous sensing of two parameters. Background Technology

[0002] In the field of micro-nano detection technology, and specifically for eddy current detection methods, there is currently no sensor design scheme that can simultaneously detect two physical quantities: micron-level displacement and ambient temperature, or nano-level metal thin film thickness and ambient temperature.

[0003] For detecting the lubricating oil film condition (thickness and ambient temperature, etc.) of friction pairs under complex operating conditions, simultaneous detection of multiple parameters requires the integration of various sensors, each typically capable of detecting only a single physical quantity. However, due to limitations in actual operating conditions, integrating multiple sensitive elements within a confined space is difficult. Furthermore, interference exists between devices at close range.

[0004] Furthermore, the impact of ambient temperature changes on sensor detection accuracy is unavoidable. Existing research on the influence of ambient temperature largely focuses on how to suppress its impact on the detection accuracy of eddy current sensors. For example, this involves using dedicated temperature sensors for ambient temperature detection or designing related algorithms for temperature compensation. These methods rely on large amounts of experimental data, increasing the cost and complexity of the measurement system.

[0005] Therefore, there is currently no convenient measurement solution using a single sensing element for multi-parameter detection, especially for the simultaneous detection of two physical quantities. Summary of the Invention

[0006] In view of this, the present invention provides an eddy current sensor detection circuit and method for realizing synchronous sensing of two parameters. For eddy current sensor devices, it provides a signal processing algorithm and its detection circuit, which can realize synchronous and rapid detection of two physical quantities—micrometer-level displacement-temperature or nanometer-level metal thin film thickness-temperature.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: an eddy current sensor detection circuit for realizing synchronous detection of dual parameters, including an excitation module, a signal conversion module, a feature component decoupling and output module, and a power supply module.

[0008] The excitation module provides a stable sinusoidal excitation signal and a reference signal to the signal conversion module and the feature component decoupling module, respectively.

[0009] Under the action of the sinusoidal excitation signal, the signal conversion module converts the impedance change of the sensitive element of the eddy current sensor into a voltage signal and outputs it.

[0010] The characteristic component decoupling module decouples the output signal of the signal conversion module.

[0011] The output module is used to amplify the input signal, improve detection sensitivity, and output the signal.

[0012] The power supply module provides a stable DC power supply for the excitation module, signal conversion module, feature component decoupling and output module in the detection circuit.

[0013] Furthermore, the excitation module includes a signal generator and a voltage follower; the signal generator outputs a stable sinusoidal excitation signal; the voltage follower is used to isolate the signal generator and the signal conversion module, eliminating the influence between the two.

[0014] Furthermore, the signal conversion module adopts an AC bridge configuration, which includes a reference coil, a detection coil, and two sampling resistors.

[0015] An AC bridge consists of four arms connected in sequence: a reference coil, a detection coil, and two sampling resistors, each on one arm. The reference coil and the detection coil are adjacent to each other, as are the two sampling resistors. The detection coil has an output port d connected to its adjacent sampling resistor, and the reference coil has an output port b connected to its adjacent sampling resistor. The voltage between b and d is the output voltage of the signal conversion module.

[0016] Furthermore, the characteristic component decoupling module includes a differential amplifier, an equal-amplitude phase-shifting circuit, a first multiplier, a second multiplier, a first low-pass filter, a second low-pass filter, and an output module;

[0017] The differential amplifier takes the output voltage signal of the signal conversion module as its input, and the output of the differential amplifier serves as one input to the first multiplier and also as one input to the second multiplier.

[0018] The constant-amplitude phase-shifting circuit takes the sinusoidal excitation signal as input, shifts the sinusoidal excitation signal by 90°, and uses it as the reference signal input for the first multiplier. Simultaneously, the sinusoidal excitation signal serves as the reference signal input for the second multiplier.

[0019] The first multiplier, the first low-pass filter, and the output module are connected in sequence.

[0020] The second multiplier, the second low-pass filter, and the output module are connected in sequence.

[0021] Furthermore, the output module includes two power amplifiers;

[0022] The first low-pass filter is connected to the first post-amplifier of the output module;

[0023] The second low-pass filter is connected to the second post-amplifier of the output module;

[0024] The outputs of the first and second stage amplifiers are the real and imaginary parts of the decoupled signal, respectively.

[0025] Another embodiment of the present invention provides a method for implementing a dual-parameter synchronous detection circuit for an eddy current sensor. The method uses the aforementioned dual-parameter synchronous detection circuit to detect both the measured parameter and the ambient temperature on the sensitive element of the eddy current sensor. The specific method is as follows:

[0026] The coil of the eddy current sensor is used as the detection coil and added to the AC bridge.

[0027] The resistance and inductance of the detection coil satisfy the following linear relationship within a certain range:

[0028]

[0029] Where Δx represents the change in the measured parameter; ΔT represents the change in ambient temperature; R0 represents the initial resistance of the detection coil; L0 represents the initial inductance of the detection coil; k a k b k c k d R(x,T) represents the function relating the resistance of the detection coil to the measured parameter x and the ambient temperature T, and L(x,T) represents the function relating the inductance of the detection coil to the measured parameter x and the ambient temperature T.

[0030] When the impedance of the detection coil satisfies the conditions ΔR << Rp + R and ΔL << L, where ΔR represents the change in resistance of the detection coil during the detection process, R represents the resistance value of the detection coil (3) during the detection process, Rp represents the resistance value of the sampling resistor, and L represents the inductance value of the detection coil (3) during the detection process; ΔL represents the change in inductance of the detection coil during the detection process. After processing by the above detection circuit, the relationship between the output voltage and the coil impedance is obtained:

[0031]

[0032] Where e(t) is the sinusoidal excitation signal, U Re U represents the real part of the voltage signal after decoupling. Im This represents the imaginary part of the voltage signal after decoupling. Except for e(t), a, b, c, and d are all constants, determined by the parameters of the signal conversion module.

[0033] Further, the measured parameter and the real and imaginary parts U of the ambient temperature and voltage are obtained. Re U Im The relationship between them:

[0034]

[0035] Where k1, k2, k3, and k4 are constant coefficients that can be obtained through subsequent experimental calibration, x0 is the initial value of the measured parameter, and T0 is the initial value of the measured ambient temperature. Except for the sinusoidal excitation signal e(t), all other coefficients are constants.

[0036] Therefore, based on the linear relationship between the real and imaginary parts of the voltage output by the eddy current sensor detection circuit that realizes simultaneous detection of dual parameters and the ambient temperature and the measured parameter, the ambient temperature and the measured parameter can be calculated simultaneously.

[0037] Furthermore, the measured parameter is a micrometer-level displacement or a nanometer-level metal thin film thickness.

[0038] Beneficial effects:

[0039] This invention provides a detection circuit and method for eddy current sensors to achieve simultaneous sensing of two parameters. Specifically for eddy current sensors, it provides signal processing algorithms and detection circuits, enabling convenient and simultaneous detection of two physical quantities—micrometer-level displacement and temperature, or nanometer-level metal thin film thickness and temperature. This invention improves the detection accuracy of eddy current sensors, addresses micro-nano detection needs, enables simultaneous detection of two parameters, and reduces the design complexity of multi-parameter simultaneous measurement systems. Attached Figure Description

[0040] Figure 1 This is a block diagram of the detection circuit of the eddy current sensor with dual-parameter synchronous sensing provided in an embodiment of the present invention.

[0041] Figure 2 A schematic diagram illustrating the basic principle of the eddy current sensor detection circuit for simultaneous dual-parameter sensing provided in an embodiment of the present invention.

[0042] Figure 3 This is a schematic diagram of the signal conversion module in the dual-parameter synchronous sensing eddy current sensor detection circuit provided in an embodiment of the present invention. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] This invention provides a detection circuit for an eddy current sensor that enables simultaneous sensing of two parameters. A feature component coupling algorithm and its detection circuit are designed for the sensitive element of the eddy current sensor, enabling simultaneous detection of two physical quantities. In the embodiments of this invention, the two physical quantities include micrometer-level displacement-ambient temperature or nanometer-level metal thin film thickness-ambient temperature.

[0045] in Figure 1 and Figure 2The diagram shows the block diagram and basic principle diagram of the dual-parameter synchronous sensing eddy current sensor detection circuit provided by the embodiment of the present invention. The detection circuit includes an excitation module, a signal conversion module, a feature component decoupling and output module, and a power supply module.

[0046] The excitation module provides a stable sinusoidal excitation signal and a reference signal to the signal conversion module and the characteristic component decoupling module. The voltage signal output by the signal conversion module contains the impedance information of the sensitive element (detection coil) of the eddy current sensor. Within the measurement range, the coil impedance component exhibits a certain linearity with the measured displacement and ambient temperature, or the measured metal film thickness and ambient temperature. Based on this, the characteristic component decoupling module extracts the coil impedance information by decoupling the real and imaginary parts of the output voltage from the signal conversion module to achieve synchronous detection of displacement / thickness and ambient temperature.

[0047] The excitation module includes a signal generator and a voltage follower. The signal generator outputs a stable sinusoidal excitation signal e(t), and the voltage follower is used to isolate the signal generator and the signal conversion module, eliminating the influence between them.

[0048] The signal conversion module can be in the form of an AC bridge, which includes a detection coil, a reference coil, and two precision cryogenic sampling resistors, such as... Figure 3 As shown in the diagram, this module converts the change in the impedance of the detection coil into a corresponding output voltage signal. Figure 3 The AC bridge consists of a reference coil 2, a detection coil 3, and two sampling resistors 4 (each with a resistance of Rp). Each of these components forms one arm of the AC bridge. The reference coil 2 and detection coil 3 are adjacent to each other, as are the two sampling resistors 4. An output port b is connected between the reference coil 2 and its adjacent sampling resistor, and an output port d is connected between the detection coil 3 and its adjacent sampling resistor. The voltage between b and d is the output voltage of the signal conversion module.

[0049] The characteristic component decoupling module includes a differential amplifier, an equal-amplitude phase-shifting circuit, a first multiplier, a second multiplier, a first low-pass filter, and a second low-pass filter.

[0050] The differential amplifier takes the output signal of the signal conversion module as its input, and its output serves as one input to the first multiplier and also as one input to the second multiplier.

[0051] The constant amplitude phase-shifting circuit takes the sinusoidal excitation signal as input, shifts the sinusoidal excitation signal by 90° and uses it as the reference signal input for the first multiplier. At the same time, the sinusoidal excitation signal is used as the reference signal input for the second multiplier.

[0052] The first multiplier, the first low-pass filter, and the first subsequent amplifier are connected in sequence.

[0053] The second multiplier, the second low-pass filter, and the second subsequent amplifier are connected in sequence.

[0054] The outputs of the first and second stage amplifiers are the real and imaginary parts of the decoupled signal, respectively.

[0055] The power module uses a low-dropout linear regulator to achieve power voltage conversion, providing a stable DC power supply for the normal operation of the detection circuit.

[0056] Another embodiment of the present invention provides a characteristic component decoupling method for the eddy current sensor detection circuit that realizes simultaneous detection of dual parameters, as detailed below:

[0057] In the current bridge, the resistance and inductance of the detection coil 3 satisfy the following linear relationship within a certain range:

[0058]

[0059] In formula (1), Δx represents the change in displacement / thickness, which in this embodiment is displacement or metal film thickness; ΔT represents the change in ambient temperature; R0 represents the initial resistance of the detection coil; L0 represents the initial inductance of the detection coil; k a k b k c k d The constant coefficients are: R(x,T) represents the function relating the resistance of the detection coil to the displacement / thickness of the measured object and the ambient temperature, and L(x,T) represents the function relating the inductance of the detection coil to the displacement / thickness of the measured object and the ambient temperature.

[0060] When the impedance of the detection coil satisfies the conditions ΔR << Rp + R and ΔL << L, where ΔR represents the change in resistance of detection coil 3 during the detection process, R represents the resistance value of detection coil 3 during the detection process, and L represents the inductance value of detection coil 3 during the detection process; ΔL represents the change in inductance of detection coil 3 during the detection process, the relationship between the output voltage and the coil impedance is obtained after passing through the detection circuit:

[0061]

[0062] In formula (2), e(t) is the excitation signal, U Re U represents the real part of the voltage. Im The imaginary part of the voltage is represented by e(t). A, b, c, and d are constants, determined by the electrical parameters of the detection circuit. Further, the relationship between displacement / thickness and ambient temperature, as well as the real and imaginary parts of the voltage, is obtained:

[0063]

[0064] In formula (3), k1, k2, k3, and k4 are calibration coefficients, which can be obtained through subsequent calibration experiments. That is, data on displacement / thickness, ambient temperature, and the real and imaginary parts of voltage are collected under a standard test environment and solved according to equation (3); x0 is the initial value of the measured displacement / thickness; T0 is the initial value of the measured ambient temperature; except for the sinusoidal excitation signal e(t), all other coefficients are constants. Thus, the ambient temperature and displacement / thickness can be calculated simultaneously based on the linear relationship between the real and imaginary parts of voltage and ambient temperature and displacement / thickness.

[0065] 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 method for realizing the synchronous detection of dual parameters using an eddy current sensor detection circuit, characterized in that, An eddy current sensor detection circuit that enables simultaneous detection of two parameters is used to detect both the measured parameter and the ambient temperature. The eddy current sensor detection circuit for realizing synchronous sensing of dual parameters is characterized in that it includes: an excitation module, a signal conversion module, a feature component decoupling and output module, and a power supply module. The excitation module provides a stable sinusoidal excitation signal to the signal conversion module and the feature component decoupling module; The signal conversion module converts the impedance change of the sensitive element of the eddy current sensor into a voltage signal and outputs it under the action of the sinusoidal excitation signal. The signal conversion module adopts an AC bridge form, which includes a reference coil (2), a detection coil (3) and two sampling resistors (4). The AC bridge is composed of four bridge arms connected in sequence. The reference coil (2), the detection coil (3) and the two sampling resistors (4) are each on one bridge arm. The reference coil (2) and the detection coil (3) are adjacent to each other, and the two sampling resistors (4) are adjacent to each other. The detection coil (3) and its adjacent sampling resistor (4) have an output port d, and the reference coil (2) and its adjacent sampling resistor (4) have an output port b. The voltage between b and d is the output voltage of the signal conversion module. The feature component decoupling module decouples the output signal of the signal conversion module; The output module is used to amplify the decoupled signal and output it. The power supply module provides a stable DC power supply for the excitation module, signal conversion module, feature component decoupling and output module in the detection circuit. The specific method is as follows: The coil of the eddy current sensor is used as the detection coil (3) and added to the AC bridge; The resistance and inductance of the detection coil (3) satisfy the following linear relationship within a certain range: (1) in, Δx This indicates the change in the measured parameter; ΔT Indicates the change in ambient temperature; R 0 indicates the initial resistance of the detection coil; L 0 indicates the initial inductance of the detection coil; k a , k b ，k c , k d The coefficient is constant. R ( x,T This indicates that the resistance of the detection coil varies with the measured parameter. x and ambient temperature T The function relating the changes in the relationship between the two, L ( x,T This indicates that the inductance of the detection coil varies with the measured parameter. x and ambient temperature T The function relating the changes in the relationship between the two; When the impedance of the detection coil (3) satisfies ΔR Rp+R , ΔL L Under certain conditions, ΔR This indicates the change in resistance of the detection coil (3) during the detection process. R This indicates the resistance value of the detection coil (3) during the detection process. Rp Indicates the resistance value of the sampling resistor. L This indicates the inductance value of the detection coil (3) during the detection process; ΔL The change in inductance of the detection coil (3) during the detection process is represented by the following relationship between the output voltage and the coil impedance after processing by the above detection circuit: (2) in e ( t ) is the sinusoidal excitation signal, U Re This represents the real part of the decoupled and amplified output voltage. U Im This represents the imaginary part of the decoupled and amplified output voltage, except... e ( t In addition to, a, b, c, d All of these are constants, determined by the electrical parameters of the detection circuit; Therefore, the real and imaginary parts of the measured parameter and the ambient temperature and voltage can be further obtained. U Re , U Im The relationship between them: (3) in k 1, k 2 ，k 3, k 4 is the calibration coefficient, obtained through subsequent experimental calibration. x 0 represents the initial value of the measured parameter. T 0 represents the initial value of the ambient temperature being measured, excluding the sinusoidal excitation signal. e ( t Except for ), all other coefficients are constants; Based on the linear relationship between the real and imaginary parts of the voltage output by the eddy current sensor detection circuit that realizes synchronous detection of dual parameters and the ambient temperature and the measured parameter, the ambient temperature and the measured parameter are calculated synchronously.

2. The eddy current sensor detection method for realizing simultaneous sensing of dual parameters as described in claim 1, characterized in that, The measured parameter is either micrometer-level displacement or nanometer-level metal thin film thickness.

3. The eddy current sensor detection method for achieving simultaneous sensing of dual parameters as described in claim 1, characterized in that, The excitation module includes a signal generator and a voltage follower; The signal generator outputs a stable sinusoidal excitation signal; The voltage follower is used to isolate the signal generator and the signal conversion module, eliminating the influence between them.

4. The eddy current sensor detection method for achieving simultaneous sensing of dual parameters as described in claims 1-3, characterized in that, The characteristic component decoupling module includes a differential amplifier, an equal-amplitude phase-shifting circuit, a first multiplier, a second multiplier, a first low-pass filter, and a second low-pass filter; The differential amplifier takes the output signal of the signal conversion module as its input, and the output of the differential amplifier serves as one input of the first multiplier and also as one input of the second multiplier. The constant amplitude phase-shifting circuit takes the sinusoidal excitation signal as input, shifts the sinusoidal excitation signal by 90° and uses it as the reference signal input for the first multiplier; at the same time, the sinusoidal excitation signal is used as the reference signal input for the second multiplier; the first multiplier is connected to the first low-pass filter; the second multiplier is connected to the second low-pass filter.

5. The eddy current sensor detection method for realizing simultaneous sensing of dual parameters as described in claim 4, characterized in that, The output module includes a first power amplifier and a second power amplifier; The output module takes the output signal of the feature component decoupling module as input, that is, the first low-pass filter is connected to the first post-amplifier; the second low-pass filter is connected to the second post-amplifier; the outputs of the first post-amplifier and the second post-amplifier are the real part and the imaginary part of the decoupled and amplified signal, respectively.

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