Conditioning circuit of eddy current induced signal and eddy current sensor

Abstract

The embodiment of the application provides a kind of eddy current sensing signal conditioning circuit and eddy current sensor, circuit includes: oscillator module, for sending excitation signal to the sensing module of eddy current sensor, excitation signal is used to trigger the oscillating electromagnetic field generated inside sensing module;Demodulation module is used for the sensing signal of sensing module output based on excitation signal and is demodulated to handle, obtains the demodulation signal of displacement information of measured object carried;Sensing signal is used to indicate the displacement of measured object detected under oscillating electromagnetic field;Output module is used for the amplification processing of demodulation signal, and the amplified demodulation signal is output.The demodulation of sensing signal is realized by the conditioning circuit provided in the application embodiment, the circuit structure is simple, without using signal conditioning chip, can effectively reduce the complexity of sensor production process, reduce cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, and particularly relates to a vortex-induced signal conditioning circuit and a vortex flow sensor. BACKGROUND

[0002] The vortex flow sensor has strong competitiveness in rotation speed measurement and displacement measurement due to its high sensitivity, high response speed, strong anti-interference capability and the like. For example, an existing rotation speed measurement vortex flow sensor mainly comprises a rotor, an induction coil, an excitation coil and a signal conditioning chip. The signal conditioning chip provides an excitation signal for the excitation coil, and the excitation coil generates a high-frequency alternating electromagnetic field after LC oscillation with a matching capacitor. In the rotation process of the rotor, a corresponding changing electromotive force is generated on the induction coil. Under the joint action of the high-frequency alternating magnetic field generated by the excitation coil and the induction electromotive force generated by the rotor, the induction coil outputs an induction signal, which is a signal modulated by a high-frequency carrier signal. The signal conditioning chip receives the induction signal output by the induction coil and demodulates the induction signal, thereby completing the rotor angle analysis.

[0003] In the demodulation process of the induction signal, the signal conditioning chip usually needs to be preprogrammed to specify the amplitude, bias and the like of the output signal after demodulation or the signal output type. The preprogramming of the signal conditioning chip is performed in the production process of the signal conditioning chip, and the introduction of the preprogramming process greatly increases the complexity of the production process and improves the production cost. SUMMARY

[0004] The vortex-induced signal conditioning circuit and the vortex flow sensor provided by the embodiments of the present application can achieve the effect of demodulating the induction signal.

[0005] In a first aspect, the embodiments of the present application provide a vortex-induced signal conditioning circuit, which is applied to a vortex flow sensor and comprises:

[0006] An oscillator module, configured to send an excitation signal to an induction module of the vortex flow sensor, the excitation signal being used to trigger the induction module to generate an oscillating electromagnetic field;

[0007] A demodulation module, configured to demodulate an induction signal output by the induction module based on the excitation signal, to obtain a demodulation signal carrying displacement information of a measured object; the induction signal being used to indicate the displacement of the measured object detected under the oscillating electromagnetic field;

[0008] An output module, configured to amplify the demodulation signal and output the amplified demodulation signal.

[0009] In a possible implementation, the demodulation module comprises:

[0010] The first processing sub-circuit is configured to generate an envelope signal corresponding to the induction signal based on the induction signal and the excitation signal.

[0011] The second processing sub-circuit is configured to detect a low-frequency component in the envelope signal to obtain a demodulation signal.

[0012] In a possible implementation, the first processing sub-circuit includes:

[0013] The addition unit is configured to superimpose the voltage of the induction signal and the excitation signal to obtain the envelope signal corresponding to the induction signal.

[0014] In a possible implementation, the addition unit includes:

[0015] The first resistor has a first end connected to an induction signal output end of the induction module.

[0016] The second resistor has a first end connected to an excitation signal output end of the oscillator module, a second end connected to a second end of the first resistor, and outputs the envelope signal corresponding to the induction signal.

[0017] In a possible implementation, the second processing sub-circuit includes:

[0018] The amplification unit is configured to amplify the envelope signal corresponding to the induction signal and output the amplified envelope signal.

[0019] The detection unit is configured to detect a low-frequency component in the amplified envelope signal to obtain the demodulation signal.

[0020] In a possible implementation, the amplification unit includes:

[0021] The first operational amplifier.

[0022] The third resistor has a first end connected to an output end of the first processing sub-circuit and a second end connected to a non-inverting input end of the first operational amplifier.

[0023] The fourth resistor has a first end connected to a ground and a second end connected to an inverting input end of the first operational amplifier.

[0024] The fifth resistor has a first end connected to an output end of the first operational amplifier and a second end connected to the inverting input end of the first operational amplifier.

[0025] In a possible implementation, the detection unit includes:

[0026] The diode has a positive electrode connected to the output end of the amplification unit and a negative electrode outputting the demodulation signal.

[0027] The first end of the first capacitor is connected with the negative electrode of the diode, and the second end of the first capacitor is grounded.

[0028] The first end of the sixth resistor is connected with the negative electrode of the diode, and the second end of the sixth resistor is grounded.

[0029] In a possible implementation, the induction signals output by the induction module are a group of differential induction signals; the demodulation module further includes a first conversion sub-circuit;

[0030] The first conversion sub-circuit is configured to combine the group of differential induction signals to obtain a single-ended induction signal.

[0031] The first processing sub-circuit is specifically configured to generate an envelope signal corresponding to the induction signal based on the single-ended induction signal and the excitation signal.

[0032] In a possible implementation, the first conversion sub-circuit includes:

[0033] The second operational amplifier;

[0034] The first end of the seventh resistor inputs a first differential signal in the group of differential induction signals, and the second end of the seventh resistor is connected with the non-inverting input end of the second operational amplifier;

[0035] The first end of the eighth resistor inputs a second differential signal in the group of differential induction signals, and the second end of the eighth resistor is connected with the inverting input end of the second operational amplifier;

[0036] The first end of the ninth resistor is connected with the output end of the second operational amplifier, and the second end of the ninth resistor is connected with the inverting input end of the second operational amplifier;

[0037] The first end of the tenth resistor is connected with the non-inverting input end of the second operational amplifier, and the second end of the tenth resistor is grounded.

[0038] In a possible implementation, the first conversion sub-circuit further includes:

[0039] The first end of the second capacitor is connected with the positive power supply end of the second operational amplifier, and the second end of the second capacitor is grounded;

[0040] The first end of the third capacitor is connected with the negative power supply end of the second operational amplifier, and the second end of the third capacitor is grounded.

[0041] In a possible implementation, the output module includes:

[0042] The second conversion sub-circuit is configured to amplify the demodulation signal and convert the amplified signal into a first target sub-signal;

[0043] The third conversion sub-circuit is configured to amplify the demodulation signal and convert the adjusted signal into a second target sub-signal, the first target sub-signal and the second target sub-signal being a group of differential signals.

[0044] In a possible implementation, the second conversion sub-circuit comprises:

[0045] The first adjustment unit is configured to adjust a direct current bias of the demodulation signal and output an adjusted demodulation signal.

[0046] The second adjustment unit is configured to amplify the adjusted demodulation signal and output the first target sub-signal.

[0047] In a possible implementation, the first adjustment unit comprises:

[0048] The eleventh resistor has a first end connected to a reference voltage.

[0049] The twelfth resistor has a first end connected to a second end of the eleventh resistor and a second end grounded.

[0050] The fourth capacitor has a first end connected to an output end of the demodulation module and a second end connected to the second end of the eleventh resistor, the first end of the twelfth resistor, and an input end of the second adjustment unit.

[0051] In a possible implementation, the second adjustment unit comprises:

[0052] The third operational amplifier has a non-inverting input end connected to the output end of the first adjustment unit.

[0053] The thirteenth resistor has a first end connected to an output end of the third operational amplifier and a second end connected to an inverting input end of the third operational amplifier.

[0054] The fourteenth resistor has a first end connected to the inverting input end of the third operational amplifier and the second end of the thirteenth resistor.

[0055] The fifth capacitor has a first end connected to the second end of the fourteenth resistor and a second end grounded.

[0056] In a possible implementation, the second adjustment unit further comprises:

[0057] The sixth capacitor has a first end connected to a positive power supply end of the third operational amplifier and a second end grounded.

[0058] The seventh capacitor has a first end connected to the output end of the third operational amplifier and a second end grounded.

[0059] In a possible implementation, the third conversion sub-circuit comprises:

[0060] a fourth operational amplifier;

[0061] a fifteenth resistor, a first end of the fifteenth resistor inputting the demodulation signal, and a second end connected to an inverting input terminal of the fourth operational amplifier;

[0062] a sixteenth resistor, a first end of the sixteenth resistor connected to a reference voltage, and a second end connected to a non-inverting input terminal of the fourth operational amplifier;

[0063] a seventeenth resistor, a first end of the seventeenth resistor connected to the non-inverting input terminal of the fourth operational amplifier, and a second end grounded;

[0064] an eighteenth resistor, a first end of the eighteenth resistor connected to an output terminal of the fourth operational amplifier, and a second end connected to the inverting input terminal of the fourth operational amplifier.

[0065] In a possible implementation, the third conversion sub-circuit further comprises at least one of an eighth capacitor and a ninth capacitor;

[0066] a first end of the eighth capacitor connected to an output terminal of the demodulation module, and a second end connected to the first end of the fifteenth resistor;

[0067] a second end of the fifteenth resistor connected to the inverting input terminal of the fourth operational amplifier;

[0068] a first end of the ninth capacitor connected to the output terminal of the fourth operational amplifier, and a second end grounded.

[0069] In a possible implementation, the oscillator module comprises:

[0070] an oscillation sub-circuit, configured to generate an oscillation signal;

[0071] a matching capacitor, configured to form a resonance loop with an excitation coil, and adjust a resonance frequency of the oscillation signal to obtain an excitation signal.

[0072] In a possible implementation, the circuit further comprises a power supply module, configured to provide power supply for the oscillator module, the demodulation module, and the output module.

[0073] In a possible implementation, the power supply module comprises:

[0074] a voltage stabilizing sub-module, configured to convert a direct-current voltage provided by an external direct-current power supply into a working voltage of the oscillator module, the demodulation module, and the output module.

[0075] In a second aspect, the embodiments of the present application provide an eddy current sensor, comprising the eddy current signal conditioning circuit mentioned in the first aspect and / or various possible implementation manners of the first aspect.

[0076] In a third aspect, the embodiments of the present application provide a displacement measuring device, comprising the eddy current sensor mentioned in the second aspect.

[0077] In a fourth aspect, the embodiments of the present application provide a vehicle, comprising the eddy current sensor mentioned in the second aspect.

[0078] The eddy current signal conditioning circuit and the eddy current sensor provided by the embodiments of the present application, the circuit comprises: an oscillator module, configured to send an excitation signal to an induction module of the eddy current sensor, the excitation signal being used to trigger the generation of an oscillating electromagnetic field inside the induction module; a demodulation module, configured to demodulate an induction signal output by the induction module based on the excitation signal, to obtain a demodulation signal carrying displacement information of a measured object; the induction signal being used to indicate the displacement of the measured object detected under the oscillating electromagnetic field; and an output module, configured to amplify the demodulation signal and output the amplified demodulation signal. The demodulation of the induction signal is realized by the conditioning circuit provided by the embodiments of the present application, the circuit structure is simple, a signal conditioning chip is not needed, the complexity of the sensor production process can be effectively reduced, and the cost can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0079] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0080] Figure 1 An exploded view of the structure of the eddy current sensor provided in an embodiment, which comprises a conditioning chip;

[0081] Figure 2 A waveform diagram of the excitation signal and the induction signal provided in an embodiment;

[0082] Figure 3 A structure of the eddy current signal conditioning circuit provided in an embodiment Figure 1 ;

[0083] Figure 4 A circuit diagram of the oscillator module provided in an embodiment;

[0084] Figure 5 A structure of the eddy current signal conditioning circuit provided in an embodiment Figure 2 ;

[0085] Figure 6 A waveform diagram of the induction signal provided in an embodiment;

[0086] Figure 7 Circuit diagram of the addition unit provided in one embodiment;

[0087] Figure 8 Schematic diagram of the second processing sub-circuit provided in one embodiment;

[0088] Figure 9 Schematic diagram of the relationship between the envelope signal and the demodulation signal provided in one embodiment;

[0089] Figure 10 Schematic diagram of the first conversion sub-circuit provided in one embodiment;

[0090] Figure 11 Schematic diagram of the second conversion sub-circuit provided in one embodiment;

[0091] Figure 12 Schematic diagram of the third conversion sub-circuit provided in one embodiment;

[0092] Figure 13 Schematic diagram of the output signal of the output module provided in one embodiment;

[0093] Figure 14 Structure explosion diagram of the eddy current sensor for measuring the rotational speed provided in one embodiment.

[0094] Reference signs:

[0095] 10: conditioning circuit of the eddy current induction signal; 101: oscillator module; 1011: oscillation sub-circuit; 1012: matching capacitor; 102: demodulation module; 103: output module; 20: induction module; L: excitation coil; T1: transistor; U1: first operational amplifier; U2: second operational amplifier; U3: third operational amplifier; U4: fourth operational amplifier.

[0096] The specific embodiments of the present application have been shown through the above-described drawings, and will be described in more detail hereinafter. These drawings and written descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0097] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The following description is made with reference to the accompanying drawings in which like reference numerals represent like elements, unless the context dictates otherwise. The following description of exemplary embodiments is not representative of all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with some aspects of the present application as detailed in the appended claims.

[0098] In the description of the present application, the terms "first", "second" are only for descriptive purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise explicitly specified and limited.

[0099] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0100] First, the nouns appearing in this paper are explained:

[0101] PCB: Printed Circuit Board, printed circuit board.

[0102] LDO: low dropout linear regulator.

[0103] ADC: analog-to-digital converter.

[0104] The eddy current sensor has strong competitiveness in speed measurement, displacement measurement and other aspects because of its high sensitivity, high response speed, strong anti-interference ability and other advantages. The working principle of the eddy current sensor is based on the eddy current effect, which is an extension of electromagnetic induction phenomenon.

[0105] The existing speed measurement eddy current induction scheme mainly consists of a rotor, an induction coil, an excitation coil and a signal conditioning chip, as shown in Figure 1 The rotor is fixed on the motor shaft as a target wheel. In order to assemble the sensor as a whole in the motor for practical application, the rotor and the PCB are hollowed in the center, and are metal disc-shaped parts with a plurality of pairs of fan-shaped induction pieces. The induction coil is at least two groups of induction coils with uniform phase difference, such as two groups of induction coils distributed in the form of SIN and COS functions on the annular PCB, and the pole pair number matches the pole pair number of the rotor. The excitation coil has a fixed inductance value, which matches the resonant capacitor to generate an alternating electromagnetic field through LC oscillation, and the resonant frequency is usually 2-5 MHz. The signal conditioning chip provides oscillation excitation for the excitation coil, receives, demodulates and outputs the induced electric signal on the induction coil. Usually, the signal conditioning chip can be preprogrammed to specify the amplitude, bias and other parameters of its output signal or the type of signal output.

[0106] The induction coil, the excitation coil, and the signal conditioning chip and its peripheral circuit of the rotating speed measurement eddy current sensor scheme are integrated on a PCB, the rotor is concentric with the coil and is 2-3 mm away from the coil plane. The signal conditioning chip can output an excitation signal to the excitation coil, the excitation coil forms an oscillating electromagnetic field around the excitation coil by forming an LC oscillation with a matching capacitor, and the oscillating electromagnetic field is a high-frequency alternating magnetic field. The external rotor is aligned with the induction coil and the excitation coil with the same center, which ensures that the rotation range of the rotor blade can completely cover the excitation and induction coils. During the rotation of the rotor, a corresponding changing electromotive force is generated on the induction coil. Under the joint action of the high-frequency alternating magnetic field generated by the excitation and the induced electromotive force generated by the rotor, an induction signal is output, which is a signal modulated by a high-frequency carrier signal, as shown in Figure 2 .

[0107] The displacement measurement scheme of the eddy current has the same principle as the rotating speed measurement scheme, and uses a moving metal sensing sheet and an alternating magnetic field to generate an induction signal for angle analysis. The main difference between the two sensors is the shape of the coil and the rotor. The PCB of the displacement measurement scheme is usually long and strip-shaped. The excitation coil is usually long and rectangular, and the induction coil is distributed on the PCB in the form of SIN and COS functions. The rectangular metal sensing sheet moves horizontally above the induction coil. The induction signal changes with the displacement of the sensing sheet above the induction coil. By analyzing the voltage signal on the induction coil, the displacement information of the rotor can be obtained.

[0108] During the demodulation of the induction signal, the signal conditioning chip usually needs to be pre-programmed to specify the amplitude, bias, and other parameters of the output signal after demodulation or the type of signal output. The pre-programming of the signal conditioning chip is performed during its production process, and the introduction of the pre-programming process will greatly increase the complexity of the production process and the production cost.

[0109] To solve the above technical problems, an eddy current induction signal conditioning circuit is provided, as shown in Figure 3 , which is applied to an eddy current sensor. The eddy current induction signal conditioning circuit 10 comprises:

[0110] An oscillator module 101 is configured to send an excitation signal to an induction module 20 of the eddy current sensor, and the excitation signal is used to trigger the induction module 20 to generate an oscillating electromagnetic field.

[0111] A demodulation module 102 is configured to demodulate an induction signal output by the induction module 20 based on the excitation signal, to obtain a demodulation signal carrying displacement information of a measured object. The induction signal is used to indicate the displacement of the measured object detected under the oscillating electromagnetic field.

[0112] An output module 103 is configured to amplify the demodulation signal and output the amplified demodulation signal.

[0113] The induction module 20 refers to a part of the eddy current sensor for sensing the displacement information of the measured object, thereby generating an induction signal carrying the displacement information of the measured object, wherein the displacement information of the measured object includes both angular displacement and linear displacement. The internal structure of the induction module 20 will be different when the types of displacement information are different, but the working principle adopted is the eddy current effect, which is not limited in the present application.

[0114] Based on the eddy current effect, the induction module 20 of the eddy current sensor needs to be in an oscillating electromagnetic field to generate an induction signal when measuring the displacement information of the measured object. In the embodiment of the present application, the oscillating electromagnetic field is triggered by the excitation signal provided by the oscillator module 101 in the conditioning circuit.

[0115] In one embodiment, the induction module 20 includes a rotor, an induction coil, and an excitation coil, the rotor is installed on the measured object, and the excitation coil is connected with the output end of the oscillator module 101. In terms of circuit structure, the circuit in the oscillator module 101 and the excitation coil together constitute an oscillation circuit to provide an excitation signal for the excitation coil, so that it can generate an oscillating electromagnetic field. Among them, the oscillation circuit composed of the circuit in the oscillator module 101 and the excitation coil has various forms, such as LC oscillation circuit, quartz crystal oscillation circuit. And the LC oscillation circuit includes various types, such as parallel resonant oscillator and series resonant oscillator, or transformer coupled oscillator and three-point oscillator. Among them, the three-point oscillator includes capacitive three-point oscillator and inductive three-point oscillator.

[0116] In one embodiment, in combination with the application scenario of the embodiment of the present application, the oscillating electromagnetic field generated in the excitation coil needs to be a high-frequency alternating magnetic field, so a capacitive three-point oscillator is adopted. As shown in Figure 4 The oscillator module 101 includes:

[0117] The oscillation sub-circuit 1011 is used to generate an oscillation signal;

[0118] Two matching capacitors 1012 are used to form a resonant loop with the excitation coil, adjust the resonant frequency of the oscillation signal, and obtain the excitation signal.

[0119] In Figure 4The circuit structure of the oscillator module 101 shown is powered by a power supply, uses the switching characteristics of transistor T1, and combines capacitors and inductors to form a stable oscillation loop. When the oscillation sub-circuit 1011 is working, transistor T1 is periodically turned on and off under the control of the base current, thereby generating an oscillation signal in the circuit. This oscillation signal reaches a stable resonant frequency through the adjustment of the two matching capacitors 1012 and the inductance of the excitation coil L, and finally provides the required excitation signal for the excitation coil.

[0120] Specifically, Figure 4 In the circuit shown, the oscillation frequency of the oscillator module 101 is:

[0121] ;

[0122] wherein, is the inductance of the excitation coil, and is the matching capacitor.

[0123] The demodulation module 102 is connected to the sensing signal output end of the sensing module 20, obtains the sensing signal carrying the displacement information of the measured object, and demodulates the sensing signal in combination with the excitation signal to obtain the demodulation signal carrying the displacement information of the measured object. In an eddy current sensor, at least two groups of sensing coils are usually included in the sensing module 20 to obtain displacement information through at least two groups of sensing signals generated in the at least two groups of sensing coils.

[0124] In the application scenario of the eddy current sensor, the conditioning circuit needs to demodulate all the sensing signals generated in the sensing module 20. For all the sensing signals, the same demodulation idea can be used for demodulation. Therefore, the demodulation module 102 includes multiple repeated minimum demodulation parts, and each minimum demodulation part is used for demodulating a group of sensing signals. In the subsequent explanation of the embodiments of the present application, only one minimum demodulation part is included in the demodulation module 102, and the demodulation process of a group of sensing signals is explained. In actual application scenarios, the number of minimum demodulation parts in the demodulation module 102 can be set according to the number of sensing signals.

[0125] For the demodulation module 102, assuming that the frequency of the excitation signal is , the signal on the excitation coil can be assumed to be:

[0126] ;

[0127] wherein, is the amplitude of the excitation signal voltage.

[0128] Let the change function of the induced voltage on the sensing coil when the rotor rotates be ,in, is the angular frequency of the motor rotor, and As the rotor rotates, the induction signal on the induction coil is:

[0129] ;

[0130] in, is the amplitude of the induced voltage.

[0131] The demodulation module 102 needs to Demodulate and obtain the displacement information of the measured object The demodulation module 102 outputs the sensing signal as a demodulated signal. There are many ways to demodulate the signal, including but not limited to multiplication demodulation, amplitude modulation (AM) demodulation, modulation and frequency modulation (FM) demodulation. Carry Partially retain and filter out high-frequency components , the induced signal can be demodulated according to the excitation signal. Since the excitation signal is provided by the oscillator module 101 in the conditioning circuit, the excitation signal can be derived through the oscillator module 101 for demodulation of the induced signal.

[0132] Specifically, multiplication demodulation mainly uses a reference signal (usually a sine wave) with the same frequency as the modulated signal to multiply the measured signal, so that the high-frequency components in the signal are converted into higher-frequency components, and then the high-frequency components are filtered out by a low-pass filter to obtain the demodulated signal. In the application scenario of this embodiment, the modulated signal is , the measured signal, that is, the sensing signal is , using the excitation signal With induction signal Multiply them and then pass them through a low-pass filter to get the demodulated signal.

[0133] Since the demodulated signal output by demodulation module 102 has a relatively small amplitude, it is amplified and output by output module 103 to facilitate subsequent displacement information analysis based on the demodulated signal. Output module 103 utilizes components with amplification effects, including but not limited to operational amplifiers and power amplifiers, and includes appropriate resistors, capacitors, and other components within the circuit to ensure stable output of the amplified signal.

[0134] The power supply of each module in the conditioning circuit can be provided by an external power supply, which directly provides the corresponding operating voltage for each module. A power supply module 104 can also be set inside the conditioning circuit, such as Figure 5As shown, the power module 104 is used to provide power supply for the oscillator module 101, the demodulation module 102 and the output module 103.

[0135] It should be noted that the power module 104 is the power interface of the conditioning circuit, which accesses the external power supply and then converts the voltage provided by the external power supply into the working voltage required in each module. The power module 104 has voltage stabilization, protection and filtering functions.

[0136] For example, in one embodiment, a voltage stabilizing submodule is included in the power module 104, which is used to convert the direct current voltage provided by the external direct current power supply into the working voltage of the oscillator module 101, the demodulation module 102 and the output module 103. Specifically, an LDO chip can be used in the voltage stabilizing submodule, which supports direct current 2.75V to 42V power supply input and can output stable circuit working voltage.

[0137] The power module 104 also includes circuit protection elements and filtering elements. The circuit protection elements can prevent reverse connection, power voltage mutation, overvoltage, overcurrent and other abnormal conditions, and the filtering elements can filter power supply noise.

[0138] In the circuit provided by the above embodiment, the circuit includes: an oscillator module, configured to send an excitation signal to an induction module of an eddy current sensor, the excitation signal being used to trigger the induction module to generate an oscillating electromagnetic field; a demodulation module, configured to demodulate an induction signal output by the induction module based on the excitation signal to obtain a demodulation signal carrying displacement information of a measured object; the induction signal is used to indicate the displacement of the measured object detected under the oscillating electromagnetic field; and an output module, configured to amplify the demodulation signal and output the amplified demodulation signal. The demodulation of the induction signal is realized by the conditioning circuit provided by the application embodiment, the circuit structure is simple, a signal conditioning chip is not needed, the complexity of the sensor production process can be effectively reduced, and the cost is reduced.

[0139] In one embodiment, the demodulation module 102 includes:

[0140] A first processing sub-circuit, configured to generate an envelope signal corresponding to the induction signal based on the induction signal and the excitation signal;

[0141] A second processing sub-circuit, configured to detect a low-frequency component in the envelope signal to obtain the demodulation signal.

[0142] The envelope signal refers to the curve of the amplitude of the signal changing over time. For the induction signal Since , the envelope of the induction signal is determined by , and the waveform diagram is as follows Figure 6The shown. And in practical applications, the induction signal is usually a complex waveform after modulation, which contains the information of carrier signal (excitation signal) and modulation signal. If direct detection is performed, it may be disturbed by the carrier signal and other high frequency components, resulting in the decline of the quality of demodulated signal.

[0143] The first processing sub-circuit is configured to generate an envelope signal corresponding to the induction signal by the induction signal and the excitation signal, separate the modulation signal and the carrier signal (excitation signal), and enhance the amplitude of the modulation signal for detection. The first processing sub-circuit can add or multiply the induction signal and the excitation signal to obtain the envelope signal corresponding to the induction signal.

[0144] In an embodiment, the first processing sub-circuit includes:

[0145] The addition unit is configured to superimpose the induction signal and the voltage of the excitation signal to obtain the envelope signal corresponding to the induction signal.

[0146] The known induction signal is , and the excitation signal is , and the amplitude of the induction voltage is usually tens of millivolts, which is not conducive to the detection of the subsequent circuit, so the excitation coil signal is superimposed with the induction signal by times to obtain the envelope signal:

[0147] ;

[0148] As the main low-frequency component in the envelope signal, the displacement information carried by the low-frequency component is detected by the second processing sub-circuit, and the demodulation signal is obtained.

[0149] In an embodiment, as shown in Figure 7 , the addition unit includes:

[0150] The first resistor R1 has a first end connected to the induction signal output end of the induction module 20.

[0151] The second resistor R2 has a first end connected to the excitation signal output end of the oscillator module 101, a second end connected to the second end of the first resistor R1, and outputs the envelope signal corresponding to the induction signal.

[0152] In Figure 7The first resistor R1 and the second resistor R2 in the shown adding circuit function as a voltage divider, which respectively reduces the voltage of the excitation signal and the induced signal to a voltage level suitable for addition, and then allows the reduced voltages to be directly added at the connection point of the first resistor R1 and the second resistor R2 based on the linear characteristics of the signals, to obtain the envelope signal. The size of the first resistor R1 and the second resistor R2 determines the size of the envelope signal.

[0153] The circuit provided in the above embodiment implements signal demodulation in an adding manner, which is simpler than a multiplication demodulation circuit, and in particular, only two resistors are used to implement signal addition, which is conducive to miniaturization of the overall structure of the conditioning circuit.

[0154] The second processing sub-circuit is mainly used for detection, and detects the low-frequency component in the envelope signal. Common detection circuits have various forms, which will not be described herein.

[0155] In one embodiment, considering that the amplitude of the excitation signal , the amplitude of the induced voltage , and the value of determined by the first resistor R1 and the second resistor R2 are not large, which is not conducive to the detection of the low-frequency component. Therefore, the second processing sub-circuit includes:

[0156] an amplifying unit, configured to amplify the envelope signal corresponding to the induced signal and output the amplified envelope signal;

[0157] a detection unit, configured to detect the low-frequency component in the amplified envelope signal to obtain a demodulated signal.

[0158] The envelope signal is amplified by the amplifying unit, and at this time, the envelope signal is , wherein is the amplification factor of the amplifying unit. Correspondingly, the demodulated signal is . After amplification, the detection is performed, which can effectively improve the detection effect of the detection unit on the low-frequency component. The amplifying unit includes but is not limited to an operational amplifier, a power amplifier and other components having an amplification effect, and corresponding resistors, capacitors and other components are arranged in the circuit to ensure stable output of the amplified signal. The detection unit can adopt a low-pass filter to filter out high-frequency components to obtain low-frequency components. The low-pass filter includes but is not limited to an RC low-pass filter and an LC low-pass filter.

[0159] In one embodiment, as shown in Figure 8 , the amplifying unit includes:

[0160] a first operational amplifier U1;

[0161] ​a third resistor R3, wherein a first end of the third resistor R3 is connected to the output end of the first processing sub-circuit, and a second end of the third resistor R3 is connected to the non-inverting input end of the first operational amplifier U1;

[0162] A fourth resistor R4, a first end of the fourth resistor R4 is grounded, and a second end is connected to the inverting input terminal of the first operational amplifier U1;

[0163] A fifth resistor R5 has a first end connected to the output end of the first operational amplifier U1 , and a second end connected to the inverting input end of the first operational amplifier U1 .

[0164] The detection unit includes:

[0165] A diode D1, wherein the anode of the diode D1 is connected to the output end of the amplifying unit, and the cathode of the diode D1 outputs the demodulated signal;

[0166] a first capacitor C1, wherein a first end of the first capacitor C1 is connected to the cathode of the diode D1, and a second end of the first capacitor C1 is grounded;

[0167] A sixth resistor R6 , wherein a first end of the sixth resistor R6 is connected to the cathode of the diode D1 , and a second end of the sixth resistor R6 is grounded.

[0168] exist Figure 8 In the circuit structure of the second processing subunit shown, the envelope signal is input to the non-inverting input of the first operational amplifier U1 via the third resistor R3. The first operational amplifier U1 has a high gain, capable of amplifying the tiny input signal to the required amplitude. The amplified signal is output from the output of the first operational amplifier U1, providing sufficient signal strength for subsequent processing.

[0169] The amplified signal is detected by diode D1. Diode D1 only allows forward current to flow. Therefore, when the input signal is in the positive half-cycle, the diode conducts, and current flows through the diode to the output terminal. When the input signal is in the negative half-cycle, the diode is cut off, and almost no current flows. Diode D1 thus performs the envelope detection function, filtering out the high-frequency components of the input signal and retaining only the low-frequency components of the envelope signal. The detected signal passes through a low-pass filter consisting of the first capacitor C1 and the sixth resistor R6. The high-frequency signal is filtered out due to the bypass effect of the capacitor, while the low-frequency signal reaches the output terminal through the sixth resistor R6, resulting in a pure demodulated signal.

[0170] Figure 8In the embodiment, the fifth resistor R5 is the feedback resistor of the first operational amplifier U1, and determines the gain of the first operational amplifier U1. The reverse input end is grounded through the fourth resistor R4 to establish a stable reference voltage, which is usually 0V (ground). The reference voltage is compared with the reference voltage of the positive input end, so as to determine the output signal of the amplifier. Grounding the fourth resistor R4 helps to prevent the first operational amplifier U1 from entering an unstable state, and improves the reliability of the circuit.

[0171] Through the circuit provided in the above embodiment, the induced signal shown in FIG. 2 can be demodulated by the adder demodulation method to obtain the envelope signal shown in FIG. 3 and the demodulation signal output after detection. Figure 6 Figure 9 The envelope signal shown in FIG. 3 and the demodulation signal output after detection can be obtained when the induced signal shown in FIG. 2 is demodulated by the adder demodulation method.

[0172] The form of the induced signal is not mentioned in the above embodiment, and it is assumed that the demodulation module 102 directly demodulates the single-ended induced signal. However, the differential signal has strong anti-interference ability, and the single-ended signal is easily disturbed by external noise. Therefore, in the design of the eddy current sensor, a set of differential induced signals is generated after a set of induced coils, and the two signals represent positive and negative polarities, respectively. The two signals are equal in amplitude and differ by 180 degrees in phase, for example, SIN+ and SIN-. For a set of differential induced signals generated by the induced coil, the differential induced signals cannot be directly received as single-ended induced signals by the circuit, but need to be converted by a conversion circuit to convert the differential induced signals into single-ended induced signals.

[0173] In one of the embodiments, the demodulation module 102 further includes a first conversion sub-circuit.

[0174] The first conversion sub-circuit is configured to combine a set of differential induced signals to obtain a single-ended induced signal.

[0175] The first processing sub-circuit is specifically configured to generate an envelope signal corresponding to the induced signal based on the single-ended induced signal and the excitation signal.

[0176] The first conversion sub-circuit can adopt various implementation manners, such as resistor voltage division and operational amplifier differential input.

[0177] In the resistor voltage division conversion, the positive and negative signals of the differential signal are divided by resistors, so that the positive and negative signals are synthesized into a single-ended signal at the output end after voltage division.

[0178] In the operational amplifier conversion, the operational amplifier amplifies the difference between the two input signals according to the input differential signal, and then outputs a corresponding single-ended signal from the output end of the operational amplifier.

[0179] ​Take a set of differential induction signals as SIN+ and SIN- as an example, Figure 10 A circuit structure diagram of a first conversion sub-circuit is provided, and the first conversion sub-circuit comprises:

[0180] A second operational amplifier U2;

[0181] A seventh resistor R7, a first end of the seventh resistor R7 inputs a first differential signal in a set of differential induction signals, and a second end is connected with a non-inverting input end of the second operational amplifier U2;

[0182] An eighth resistor R8, a first end of the eighth resistor R8 inputs a second differential signal in the set of differential induction signals, and a second end is connected with an inverting input end of the second operational amplifier U2;

[0183] A ninth resistor R9, a first end of the ninth resistor R9 is connected with an output end of the second operational amplifier U2, and a second end is connected with the inverting input end of the second operational amplifier U2;

[0184] A tenth resistor R10, a first end of the tenth resistor R10 is connected with the non-inverting input end of the second operational amplifier U2, and a second end is grounded.

[0185] In the circuit shown in Figure 10 , a set of differential induction signals SIN+ and SIN- are input into the second operational amplifier U2 through the eighth resistor R8 and the seventh resistor R7. The second operational amplifier U2 is the core of the circuit, used for amplifying and converting input signals, and it converts the received set of differential induction signals SIN+ and SIN- into a single-ended induction signal SIN and outputs from the output end. Among them, the seventh resistor R7 and the eighth resistor R8 are used to set the impedance of the input signal and participate in the reception of the differential induction signal. The ninth resistor R9 is a feedback resistor, which determines the gain of the second operational amplifier U2. The tenth resistor R10 is grounded, which is used to connect the non-inverting input end of the second operational amplifier U2 to the ground to form a single-ended output.

[0186] In addition, the circuit shown in Figure 10 also includes a second capacitor C2 and a third capacitor C3:

[0187] A first end of the second capacitor C2 is connected with a positive power supply end of the second operational amplifier U2, and a second end is grounded;

[0188] A first end of the third capacitor C3 is connected with a negative power supply end of the second operational amplifier U2, and a second end is grounded.

[0189] Among them, the second capacitor C2 and the third capacitor C3 are used as bypass capacitors for the power supply pin to stabilize the input power supply voltage.

[0190] The demodulation module 102 processes the sensing signal to extract the portion of the sensing signal that carries the displacement information of the object being measured. However, the amplitude of the demodulated signal is usually around a few hundred millivolts, and its quality and usability are limited. , it is necessary to improve the quality and usability of the demodulated signal, including but not limited to offset adjustment, linearization, and amplitude adjustment. In the embodiment of the present application, the demodulated signal is amplified by the output module 103 to output a usable demodulated signal. The demodulated signal and the amplified demodulated signal are both single-ended sensing signals. In some embodiments, in order to ensure the quality of the amplified demodulated signal received in the subsequent module, it is necessary to convert it into a differential signal for transmission.

[0191] Accordingly, a single-ended sensing signal needs to be converted into a set of differential signals. There are two main methods for converting single-ended signals to differential signals: active device conversion and passive device conversion. Active device conversion uses an amplifier to convert single-ended signals into differential signals. The single-ended signal is input to one input of the amplifier, and the amplifier's in-phase and inverting outputs output a non-inverting signal and an inverted signal, respectively, with half the original amplitude. Passive device conversion uses a balun or transformer to convert single-ended signals into differential signals. These devices utilize the characteristics of transformers to convert AC signals into differential signals with opposite phases and equal amplitudes. A single-ended signal is input to one input of a balun or transformer, and through its internal structure and the principle of electromagnetic induction, a pair of differential signals are output.

[0192] Based on an operational amplifier, in one embodiment, the output module 103 includes:

[0193] a second conversion sub-circuit, configured to amplify the demodulated signal and convert the amplified signal into a first target sub-signal;

[0194] The third conversion sub-circuit is used to amplify the demodulated signal and convert the adjusted signal into a second target sub-signal, where the first target sub-signal and the second target sub-signal are a group of differential signals.

[0195] The amplification processing of the demodulated signal includes amplitude adjustment and adding a DC bias. The single-ended signal is converted into a set of differential signals through the second conversion sub-circuit and the third conversion sub-circuit.

[0196] Specifically, the second conversion sub-circuit includes:

[0197] a first adjustment unit, configured to adjust a DC bias of a demodulated signal and output an adjusted demodulated signal;

[0198] The second adjusting unit is configured to amplify the adjusted demodulation signal and output a first target sub-signal.

[0199] As shown in Figure 11 The first adjusting unit comprises:

[0200] The eleventh resistor R11 has a first end connected to a reference voltage Vref;

[0201] The twelfth resistor R12 has a first end connected to a second end of the eleventh resistor R11 and a second end grounded;

[0202] The fourth capacitor C4 has a first end connected to an output end of the demodulation module and a second end connected to the second end of the eleventh resistor R11, the first end of the twelfth resistor R12 and an input end of the second adjusting unit.

[0203] The second adjusting unit comprises:

[0204] The third operational amplifier U3 has a non-inverting input end connected to an output end of the first adjusting unit;

[0205] The thirteenth resistor R13 has a first end connected to an output end of the third operational amplifier U3 and a second end connected to an inverting input end of the third operational amplifier U3;

[0206] The fourteenth resistor R14 has a first end connected to the inverting input end of the third operational amplifier U3;

[0207] The fifth capacitor C5 has a first end connected to a second end of the fourteenth resistor R14 and a second end grounded.

[0208] The second adjusting unit further comprises:

[0209] The sixth capacitor C6 has a first end connected to a positive power supply end of the third operational amplifier U3 and a second end grounded;

[0210] The seventh capacitor C7 has a first end connected to the output end of the third operational amplifier U3 and a second end grounded.

[0211] In Figure 11In the circuit structure shown, the third operational amplifier U3 is the core element of the circuit, which receives a single-ended sensing signal SIN (demodulation signal) as input, and outputs a differential signal SIN+ (first target sub-signal) after internal amplification and filtering processing. The eleventh resistor R11 and the twelfth resistor R12 are resistors used for adding DC bias, and adjusting the ratio of the eleventh resistor R11 and the twelfth resistor R12 will change the DC level of the input end and the DC component of the output end. The fourth capacitor C4 is used for AC coupling to isolate the DC component in the original demodulation signal. The thirteenth resistor R13, the fourteenth resistor R14 and the fifth capacitor C5 constitute a feedback loop of the AC amplification circuit. The AC amplification ratio is (1+R13 / R14), and the DC amplification ratio is 1. The sixth capacitor C6 is a bypass capacitor. The seventh capacitor C7 is used to filter high-frequency noise in the output signal and improve the purity of the output signal.

[0212] In summary, the circuit converts the single-ended SIN signal into a differential SIN+ signal through the differential amplifier configuration of the third operational amplifier U3. At the same time, through the cooperation of resistors and capacitors, the circuit realizes the functions of gain adjustment, stability enhancement and noise filtering of the signal.

[0213] In one embodiment, as shown in Figure 12 The third conversion sub-circuit includes:

[0214] a fourth operational amplifier U4;

[0215] a fifteenth resistor R15, a first end of the fifteenth resistor R15 inputting the demodulation signal, and a second end of the fifteenth resistor R15 connected with an inverting input terminal of the fourth operational amplifier U4;

[0216] a sixteenth resistor R16, a first end of the sixteenth resistor R16 connected with a reference voltage Vref, and a second end of the sixteenth resistor R16 connected with a non-inverting input terminal of the fourth operational amplifier U4;

[0217] a seventeenth resistor R17, a first end of the seventeenth resistor R17 connected with the non-inverting input terminal of the fourth operational amplifier U4, and a second end of the seventeenth resistor R17 grounded;

[0218] an eighteenth resistor R18, a first end of the eighteenth resistor R18 connected with an output terminal of the fourth operational amplifier U4, and a second end of the eighteenth resistor R18 connected with the inverting input terminal of the fourth operational amplifier U4.

[0219] The third conversion sub-circuit further includes at least one of an eighth capacitor C8 and a ninth capacitor C9;

[0220] a first end of the eighth capacitor C8 connected with an output terminal of the demodulation module, and a second end of the eighth capacitor C8 connected with the first end of the fifteenth resistor R15;

[0221] The second end of the fifteenth resistor R15 is connected with the inverting input end of the fourth operational amplifier U4.

[0222] The first end of the ninth capacitor C9 is connected with the output end of the fourth operational amplifier U4, and the second end is grounded.

[0223] In the circuit shown in Figure 12 , the fifteenth resistor R15 and the eighteenth resistor R18 determine the gain of the fourth operational amplifier U4. The calculation of the gain is based on the resistance ratio of the fifteenth resistor R15 and the eighteenth resistor R18, specifically gain = R15 / R18. In this way, the circuit can adjust the amplitude of the input single-ended sensing signal SIN.

[0224] The sixteenth resistor R16 and the seventeenth resistor R17 are used to set the bias voltage of the fourth operational amplifier U4. By adjusting the resistance value of the sixteenth resistor R16, the input level of the non-inverting input end of the operational amplifier can be changed, thereby realizing the direct current bias adjustment of the output signal.

[0225] The fourth operational amplifier U4 is the core component of the second processing sub-circuit, responsible for amplifying and processing the input signal. Its gain is determined by the fifteenth resistor R15 and the eighteenth resistor R18, while the input and output ends are connected to the circuit through other elements to realize the conversion and adjustment of the signal.

[0226] The eighth capacitor C8 is used for AC coupling to isolate the direct current component in the original demodulated signal.

[0227] The ninth capacitor C9 is connected between the output end of the fourth operational amplifier U4 and the ground. It is used to filter out high-frequency noise in the output signal and improve the purity of the output signal.

[0228] In the circuit shown in Figure 11 and Figure 12 , the fifteenth capacitor C15 is used as a bypass capacitor for the power supply pin to stabilize the input power supply voltage and provide a stable reference voltage Vref.

[0229] In one embodiment, when two groups of induction coils are included in the induction module 20, the processing of the circuit in Figure 11 and Figure 12 sets the direct current bias of the output signal to VDD / 2 (2.5V), and the two groups of differential signals output by the output module 103 are as shown in Figure 13 In one embodiment, the output module 103 outputs two groups of differential signals to the MCU, and the four-way ADC port on the MCU receives four-way differential signals and converts them into digital signals. After analysis, the four-way differential input signals can be converted into two-way single-ended signals:

[0230] ;

[0231] ;

[0232] wherein, is the parsed voltage amplitude. Thus, displacement information can be obtained from the following formula :

[0233] ;

[0234] This information can be used in motor position detection, motor speed detection, and other detection scenarios.

[0235] Based on the same idea as described above, the embodiments of the present application also provide an eddy current sensor, which includes a sensing module and the conditioning circuit of the eddy current sensing signal mentioned in any of the above embodiments.

[0236] Specifically, in one embodiment, as shown in Figure 14 , an eddy current sensor for measuring rotational speed includes a rotor, two groups of sensing coils, an excitation coil, and a conditioning circuit. The sensing coils, the excitation coil, and the conditioning circuit are on a PCB board, and the rotor is fixed at a distance of 2-3 mm from the center of the coil. The overall circuit is composed of a coil part and a circuit part. The coil part is circular, with the lower half connected to the circuit board, and a circular hollow in the middle. The excitation coil and the sensing coil are distributed in a closed circular manner.

[0237] The excitation coil is distributed on the outermost coil of the coil part, which is a complete multi-turn circular coil, with one end leading to an oscillator module 101 connected to the circuit. The sensing coil is distributed inside the excitation coil, with the outermost coil close to the innermost turn of the excitation coil. Such a design can make the sensing coil produce a uniform induced electromotive force when the magnetic field generated by the excitation coil changes uniformly and at a high frequency. The sensing coil is composed of two groups of specific shape coils that do not intersect each other and have a phase difference of 90°. The two groups of sensing coils are connected to the demodulation module 102 in the conditioning circuit in a differential manner, providing four differential signal inputs.

[0238] The metal rotor is fixed on the motor rotating shaft, and the fan-shaped blades on the rotor just cover the whole induction coil. The pole number of the fan-shaped blades corresponds to the pole pair number of the induction coil. While the motor rotates, the rotor rotates above the induction coil at the same speed. Under the influence of the alternating excitation magnetic field (3-5 MHz) of the coil, the rotor surface generates an induced eddy current, and the induced magnetic field of the eddy current is opposite to the excitation magnetic field, thereby offsetting a part of the alternating magnetic field (when the rotor rotates, the surface generates an electromagnetic field opposite to the excitation magnetic field, so that the excitation magnetic field of the induction coil covered by the rotor is weakened). With the rotation of the rotor, the output of the induction coil changes in a SIN shape under the action of the eddy current, and the change frequency is equal to the product of the motor rotation frequency and the rotor pole pair number. Therefore, when the sensor and the motor work at the same time, the signal output by the induction coil can be regarded as a SIN-shaped signal modulated by a high-frequency signal.

[0239] The embodiment of the present application also provides a displacement measuring device, and the device comprises the eddy current sensor.

[0240] The embodiment of the present application also provides a vehicle, and the vehicle comprises the eddy current sensor.

Claims

1. A conditioning circuit for eddy current induction signals, characterized in that: The circuit is applied to an eddy current sensor, and the circuit includes: an oscillator module, configured to send an excitation signal to an excitation coil in the induction module of the eddy current sensor, wherein the excitation signal is configured to trigger generation of an oscillating electromagnetic field inside the induction module; a demodulation module, configured to process the excitation signal to obtain an n-fold excitation signal, where n is greater than 0, and superimpose the n-fold excitation signal with the voltage of the induction signal output by the induction coil of the induction module to obtain an envelope signal corresponding to the induction signal, and obtain a demodulation signal carrying displacement information of the measured object based on the envelope signal; the induction signal is used to indicate the displacement of the measured object detected under the oscillating electromagnetic field; The output module is used to amplify the demodulated signal and output the amplified demodulated signal.

2. The circuit according to claim 1, wherein: The demodulation module includes: a first processing sub-circuit, configured to process the excitation signal to obtain an n-fold excitation signal, and superimpose the sensing signal with a voltage of the n-fold excitation signal to obtain an envelope signal corresponding to the sensing signal; The second processing sub-circuit is used to detect the low-frequency component in the envelope signal to obtain the demodulated signal.

3. The circuit according to claim 2, characterized in that The first processing sub-circuit includes: a first resistor, wherein a first end of the first resistor is connected to a sensing signal output end of the sensing module; A second resistor, wherein a first end of the second resistor is connected to the excitation signal output end of the oscillator module, a second end of the second resistor is connected to the second end of the first resistor, and outputs an envelope signal corresponding to the sensing signal.

4. The circuit according to claim 2, characterized in that The second processing sub-circuit includes: an amplifying unit, configured to amplify an envelope signal corresponding to the sensing signal and output the amplified envelope signal; The detection unit is used to detect the low-frequency component in the amplified envelope signal to obtain the demodulated signal.

5. The circuit according to claim 4, characterized in that The amplification unit includes: a first operational amplifier; a third resistor, wherein a first end of the third resistor is connected to the output end of the first processing sub-circuit, and a second end of the third resistor is connected to the non-inverting input end of the first operational amplifier; a fourth resistor, wherein a first end of the fourth resistor is grounded, and a second end of the fourth resistor is connected to the inverting input terminal of the first operational amplifier; a fifth resistor, wherein a first end of the fifth resistor is connected to the output end of the first operational amplifier, and a second end of the fifth resistor is connected to the inverting input end of the first operational amplifier.

6. The circuit according to claim 4, characterized in that The detection unit includes: a diode, wherein the anode of the diode is connected to the output end of the amplifying unit, and the cathode of the diode outputs the demodulated signal; a first capacitor, wherein a first end of the first capacitor is connected to the cathode of the diode, and a second end of the first capacitor is grounded; a sixth resistor, wherein a first end of the sixth resistor is connected to the cathode of the diode, and a second end of the sixth resistor is grounded.

7. The circuit according to claim 2, characterized in that The sensing signal output by the sensing module is a set of differential sensing signals; the demodulation module further includes a first conversion sub-circuit; The first conversion sub-circuit is configured to combine the set of differential sensing signals to obtain a single-ended sensing signal; The first processing sub-circuit is specifically configured to generate an envelope signal corresponding to the sensing signal based on the single-ended sensing signal and the excitation signal.

8. The circuit according to claim 7, characterized in that The first conversion sub-circuit includes: a second operational amplifier; a seventh resistor, wherein a first end of the seventh resistor is input with the first differential signal in the set of differential sensing signals, and a second end of the seventh resistor is connected to the non-inverting input terminal of the second operational amplifier; an eighth resistor, wherein a first end of the eighth resistor is input with the second differential signal in the set of differential sensing signals, and a second end of the eighth resistor is connected to the inverting input terminal of the second operational amplifier; a ninth resistor, wherein a first end of the ninth resistor is connected to the output end of the second operational amplifier, and a second end of the ninth resistor is connected to the inverting input end of the second operational amplifier; a tenth resistor, wherein a first end of the tenth resistor is connected to the non-inverting input terminal of the second operational amplifier, and a second end of the tenth resistor is grounded.

9. The circuit according to claim 8, characterized in that The first conversion sub-circuit further includes: a second capacitor, wherein a first end of the second capacitor is connected to the positive power supply terminal of the second operational amplifier, and a second end of the second capacitor is grounded; A third capacitor, wherein a first end of the third capacitor is connected to the negative power supply terminal of the second operational amplifier, and a second end of the third capacitor is grounded.

10. The circuit according to claim 1, wherein: The output module includes: a second conversion sub-circuit, configured to amplify the demodulated signal and convert the amplified signal into a first target sub-signal; The third conversion sub-circuit is configured to amplify the demodulated signal and convert the adjusted signal into a second target sub-signal, where the first target sub-signal and the second target sub-signal are a set of differential signals.

11. The circuit according to claim 10, characterized in that The second conversion sub-circuit includes: a first adjustment unit, configured to adjust a DC bias of the demodulated signal and output the adjusted demodulated signal; The second adjustment unit is configured to amplify the adjusted demodulated signal and output the first target sub-signal.

12. The circuit according to claim 11, characterized in that The first adjustment unit includes: an eleventh resistor, a first end of the eleventh resistor being connected to a reference voltage; a twelfth resistor, a first end of the twelfth resistor being connected to the second end of the eleventh resistor, and a second end of the twelfth resistor being grounded; a fourth capacitor, wherein a first end of the fourth capacitor is connected to the output end of the demodulation module, and a second end of the fourth capacitor is connected to the second end of the eleventh resistor, the first end of the twelfth resistor, and the input end of the second adjustment unit.

13. The circuit according to claim 11, characterized in that The second adjustment unit includes: a third operational amplifier, wherein a non-inverting input terminal of the third operational amplifier is connected to an output terminal of the first adjustment unit; a thirteenth resistor, wherein a first end of the thirteenth resistor is connected to the output end of the third operational amplifier, and a second end of the thirteenth resistor is connected to the inverting input end of the third operational amplifier; a fourteenth resistor, a first end of the fourteenth resistor being connected to the inverting input end of the third operational amplifier and the second end of the thirteenth resistor; A fifth capacitor, wherein a first end of the fifth capacitor is connected to the second end of the fourteenth resistor, and a second end of the fifth capacitor is grounded.

14. The circuit according to claim 13, characterized in that The second adjustment unit further includes: a sixth capacitor, wherein a first end of the sixth capacitor is connected to the positive power supply terminal of the third operational amplifier, and a second end of the sixth capacitor is grounded; A seventh capacitor, wherein a first end of the seventh capacitor is connected to the output end of the third operational amplifier, and a second end of the seventh capacitor is grounded.

15. The circuit according to claim 10, wherein: The third conversion sub-circuit includes: a fourth operational amplifier; a fifteenth resistor, wherein a first end of the fifteenth resistor is input with the demodulated signal, and a second end of the fifteenth resistor is connected to the inverting input end of the fourth operational amplifier; a sixteenth resistor, wherein a first end of the sixteenth resistor is connected to the reference voltage, and a second end of the sixteenth resistor is connected to the non-inverting input terminal of the fourth operational amplifier; a seventeenth resistor, wherein a first end of the seventeenth resistor is connected to the non-inverting input terminal of the fourth operational amplifier, and a second end of the seventeenth resistor is grounded; An eighteenth resistor, wherein a first end of the eighteenth resistor is connected to the output end of the fourth operational amplifier, and a second end of the eighteenth resistor is connected to the inverting input end of the fourth operational amplifier.

16. The circuit according to claim 15, characterized in that The third conversion sub-circuit further includes at least one of an eighth capacitor and a ninth capacitor; A first end of the eighth capacitor is connected to the output end of the demodulation module, and a second end is connected to the first end of the fifteenth resistor; The second end of the fifteenth resistor is connected to the inverting input terminal of the fourth operational amplifier; A first end of the ninth capacitor is connected to the output end of the fourth operational amplifier, and a second end thereof is grounded.

17. The circuit according to claim 1, wherein: The induction module includes an excitation coil, and the oscillator module includes: an oscillator subcircuit, the oscillator subcircuit being configured to generate an oscillation signal; The two matching capacitors are used to form a resonant circuit with the excitation coil, adjust the resonant frequency of the oscillation signal, and obtain the excitation signal.

18. The circuit according to any one of claims 1 to 17, characterized in that: The circuit further includes a power supply module, which is used to provide power to the oscillator module, the demodulation module and the output module.

19. The circuit according to claim 18, characterized in that The power module includes: The voltage stabilizing submodule is used to convert the DC voltage provided by the external DC power supply into the operating voltage of the oscillator module, the demodulation module and the output module.

20. An eddy current sensor, characterized in that: The eddy current sensor includes a sensing module and a conditioning circuit for eddy current induction signals according to any one of claims 1 to 19.

21. A displacement measuring device, characterized in that: The device comprises the eddy current sensor according to claim 20.

22. A vehicle, characterized in that: The vehicle includes the eddy current sensor according to claim 20.

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