Eddy current sensing signal conditioning circuit and eddy current sensor

Abstract

The embodiment of the invention provides an eddy current induction signal conditioning circuit and an eddy current sensor, and the circuit comprises an oscillator module which is used for transmitting an excitation signal to an induction module of the eddy current sensor, and the excitation signal is used for triggering the interior of the induction module to generate an oscillation electromagnetic field; the demodulation module is used for demodulating the induction signal output by the induction module based on the excitation signal to obtain a demodulation signal carrying displacement information of the measured object; the induction signal is used for indicating the displacement of the detected object under the oscillation electromagnetic field; and the output module is used for amplifying the demodulation signal and outputting the amplified demodulation signal. Through the conditioning circuit provided by the embodiment of the invention, demodulation of the sensing signal is realized, the circuit structure is simple, a signal conditioning chip does not need to be used, the complexity of a sensor production process can be effectively reduced, and the cost is reduced.

Description

Technical Field

[0001] This application relates to the technical field of sensors, and particularly to a conditioning circuit for eddy current induction signals and an eddy current sensor. Background Art

[0002] Eddy current sensors have strong competitiveness in rotational speed measurement, displacement measurement, etc. due to their advantages such as high sensitivity, high response speed, and strong anti-interference ability. For example, existing rotational speed measurement eddy current sensors mainly consist of 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 after the excitation coil and the matching capacitor generate an LC oscillation, a high-frequency alternating electromagnetic field is produced. During the rotation of the rotor, a corresponding changing electromotive force is generated on the induction coil. Under the combined action of the high-frequency alternating magnetic field generated by the excitation coil and the induced electromotive force generated by the rotor, the induction coil outputs an induction signal - a signal modulated by a high-frequency carrier signal. The signal conditioning chip receives the induction signal output by the induction coil and demodulates it to complete the analysis of the rotor angle.

[0003] During the demodulation process of the induction signal, the signal conditioning chip usually needs to be pre-programmed to specify parameters such as the amplitude and offset of the output signal after demodulation or the signal output type. And the pre-programming of the signal conditioning chip is carried out during its production process. Introducing the pre-programming process will greatly increase the complexity of the production process and raise the production cost. Summary of the Invention

[0004] Embodiments of this application provide a conditioning circuit for eddy current induction signals and an eddy current sensor to achieve the effect of demodulating the induction signal.

[0005] In a first aspect, embodiments of this application provide a conditioning circuit for eddy current induction signals. The circuit is applied to an eddy current sensor and includes:

[0006] An oscillator module for sending an excitation signal to the induction module of the eddy current sensor, where the excitation signal is used to trigger the generation of an oscillating electromagnetic field inside the induction module;

[0007] A demodulation module for demodulating the induction signal output by the induction module based on the excitation signal to obtain a demodulated signal carrying the displacement information of the measured object; the induction signal is used to indicate the displacement of the measured object detected under the oscillating electromagnetic field;

[0008] An output module for amplifying the demodulated signal and outputting the amplified demodulated signal.

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

[0010] A first processing sub - circuit for generating an envelope signal corresponding to the induction signal based on the induction signal and the excitation signal;

[0011] A second processing sub - circuit for detecting the low - frequency component in the envelope signal to obtain a demodulated signal.

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

[0013] An addition unit for superimposing the voltages of the induction signal and the excitation signal to obtain an envelope signal corresponding to the induction signal.

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

[0015] A first resistor, the first end of which is connected to the induction signal output end of the induction module;

[0016] A second resistor, the first end of which is connected to the excitation signal output end of the oscillator module, and the second end is connected to the second end of the first resistor to output an envelope signal corresponding to the induction signal.

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

[0018] An amplification unit for amplifying the envelope signal corresponding to the induction signal and outputting the amplified envelope signal;

[0019] A detection unit for detecting the low - frequency component in the amplified envelope signal to obtain a demodulated signal.

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

[0021] A first operational amplifier;

[0022] A third resistor, the first end of which is connected to the output end of the first processing sub - circuit, and the second end is connected to the non - inverting input terminal of the first operational amplifier;

[0023] A fourth resistor, the first end of which is grounded, and the second end is connected to the inverting input terminal of the first operational amplifier;

[0024] A fifth resistor, the first end of which is connected to the output end of the first operational amplifier, and the second end is connected to the inverting input terminal of the first operational amplifier.

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

[0026] A diode, the positive pole of which is connected to the output end of the amplification unit, and the negative pole outputs the demodulated signal;

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

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

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

[0030] The first conversion sub-circuit is used to combine a 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 manner, the first conversion sub-circuit includes:

[0033] The second operational amplifier;

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

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

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

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

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

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

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

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

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

[0043] A third conversion sub - circuit, 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.

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

[0045] A first adjustment unit, configured to adjust the DC bias of the demodulated signal and output the adjusted demodulated signal;

[0046] A second adjustment unit, configured to amplify the adjusted demodulated signal and output the first target sub - signal.

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

[0048] An eleventh resistor, the first end of the eleventh resistor is connected to a reference voltage;

[0049] A twelfth resistor, the first end of the twelfth resistor is connected to the second end of the eleventh resistor, and the second end is grounded;

[0050] A fourth capacitor, the first end of the fourth capacitor is connected to the output end of the demodulation module, and the second end 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.

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

[0052] A third operational amplifier, the non - inverting input terminal of the third operational amplifier is connected to the output end of the first adjustment unit;

[0053] A thirteenth resistor, the first end of the thirteenth resistor is connected to the output end of the third operational amplifier, and the second end is connected to the inverting input terminal of the third operational amplifier;

[0054] A fourteenth resistor, the first end of the fourteenth resistor is connected to the inverting input terminal of the third operational amplifier and the second end of the thirteenth resistor;

[0055] A fifth capacitor, the first end of the fifth resistor is connected to the second end of the fourteenth resistor, and the second end is grounded.

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

[0057] A sixth capacitor, the first end of the sixth capacitor is connected to the positive power supply terminal of the third operational amplifier, and the second end is grounded;

[0058] A seventh capacitor, the first end of the seventh capacitor is connected to the output end of the third operational amplifier, and the second end is grounded.

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

[0060] A fourth operational amplifier;

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

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

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

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

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

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

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

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

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

[0070] An oscillation sub-circuit for generating an oscillation signal;

[0071] A matching capacitor for forming a resonant circuit with the excitation coil to adjust the resonant frequency of the oscillation signal to obtain an excitation signal.

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

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

[0074] A voltage regulation sub-module for converting the DC voltage provided by an external DC power supply into the operating voltages of the oscillator module, the demodulation module, and the output module.

[0075] In a second aspect, an embodiment of the present application provides an eddy current sensor, including a conditioning circuit for eddy current induction signals as mentioned in the first aspect above and / or various possible implementation manners of the first aspect.

[0076] In a third aspect, an embodiment of the present application provides a displacement measurement device, including the eddy current sensor as mentioned in the second aspect above.

[0077] In a fourth aspect, an embodiment of the present application provides a vehicle, including the eddy current sensor as mentioned in the second aspect above.

[0078] The conditioning circuit for eddy current induction signals and the eddy current sensor provided by the embodiments of the present application, the circuit includes: an oscillator module for sending an excitation signal to the induction module of the eddy current sensor, and the excitation signal is used to trigger the generation of an oscillating electromagnetic field inside the induction module; a demodulation module for demodulating the induction signal output by the induction module based on the excitation signal to obtain a demodulation signal carrying the displacement information of the object to be measured; the induction signal is used to indicate the displacement of the object to be measured detected under the oscillating electromagnetic field; an output module for amplifying the demodulation signal and outputting the amplified demodulation signal. By using the conditioning circuit provided by the embodiments of the application to realize the demodulation of the induction signal, the circuit structure is simple, there is no need to use a signal conditioning chip, which can effectively reduce the complexity of the sensor production process and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] The drawings here are incorporated into the description and form a part of this description, showing embodiments consistent with the present application, and are used together with the description to explain the principles of the present application.

[0080] Figure 1 It is an exploded view of the structure of an eddy current sensor including a conditioning chip provided in an embodiment;

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

[0082] Figure 3 It is the structure of a conditioning circuit for eddy current induction signals provided in an embodiment Figure 1 ;

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

[0084] Figure 5 It is the structure of a conditioning circuit for eddy current induction signals provided in an embodiment Figure 2 ;

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

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

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

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

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

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

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

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

[0093] Figure 14 The exploded view of the structure of the eddy current sensor for rotational speed measurement provided in one embodiment.

[0094] Reference numerals:

[0095] 10: Conditioning circuit for eddy current induction signal; 101: Oscillator module; 1011: Oscillator 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] Through the above - mentioned drawings, specific embodiments of the present application have been shown, and there will be more detailed descriptions hereinafter. These drawings and textual 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 implementation manners

[0097] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numerals in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present application. On the contrary, they are merely examples of the devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0098] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more unless otherwise specifically defined.

[0099] In the description of this application, it should be noted that unless otherwise clearly stipulated and defined, the terms "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

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

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

[0102] LDO: Low Dropout Linear Regulator.

[0103] ADC: Analog-to-Digital Converter.

[0104] Eddy current sensors have strong competitiveness in rotational speed measurement, displacement measurement, etc. due to their advantages such as high sensitivity, high response speed, and strong anti-interference ability. The working principle of eddy current sensors is based on the eddy current effect, which is an extension of electromagnetic induction.

[0105] Existing eddy current induction schemes for rotational speed measurement mainly consist of a rotor, an induction coil, an excitation coil, and a signal conditioning chip, as Figure 1 shown. The rotor is fixed on the motor shaft as the target wheel. For the overall assembly of the sensor inside the motor during actual application, the rotor and the PCB are metal parts in the shape of a wheel disc with a hollow center and several pairs of fan-shaped induction pieces. The induction coil is at least two groups of induction coils with a uniform phase difference. For example, two groups of induction coils are distributed on the annular PCB in the forms of SIN and COS functions respectively, and the number of pole pairs thereof matches the number of pole pairs of the rotor. The excitation coil has a fixed inductance value and can generate an alternating electromagnetic field through LC oscillation after matching with the resonant capacitor. The resonant frequency is usually 2 - 5 MHz. The function of the signal conditioning chip is to provide an oscillation excitation for the excitation coil, receive, demodulate, and output the induced electrical signal on the induction coil. Usually, the signal conditioning chip can be pre-programmed to specify parameters such as the amplitude and offset of its output signal or the type of signal output.

[0106] For the eddy current sensor solution for rotational speed measurement, the induction coil, excitation coil, signal conditioning chip and its peripheral circuits are integrated on a single PCB. The rotor is concentric with the coil and is 2-3 millimeters away from the coil plane. The signal conditioning chip can output an excitation signal to the excitation coil. The excitation coil forms an LC oscillation with a matching capacitor to create an oscillating electromagnetic field around the excitation coil. The oscillating electromagnetic field is a high-frequency alternating magnetic field. The external rotor is centered and aligned with the induction coil and the excitation coil to ensure that the rotation range of the rotor blades 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 combined action of the high-frequency alternating magnetic field generated by the excitation and the induced electromotive force generated by the rotor, an induced signal is output - a signal modulated by a high-frequency carrier signal, such as Figure 2 as shown.

[0107] The principle of the eddy current displacement measurement solution is the same as that of the rotational speed measurement solution. A moving metal induction sheet is used to generate an induced signal with an alternating magnetic field for angle resolution. The main difference between the two sensors lies in the shapes of the coil and the rotor. The PCB of the displacement measurement solution is usually long and strip-shaped. The excitation coil is usually long and rectangular, and the induction coils are distributed on the PCB in the form of SIN and COS functions. The rectangular metal induction sheet moves horizontally above the induction coils. The induced signal changes with the displacement of the induction sheet above the induction coils. By analyzing the voltage signal on the induction coils, the displacement information of the rotor can be obtained.

[0108] During the demodulation process of the induced signal, the signal conditioning chip usually needs to be pre-programmed to specify parameters such as the amplitude and offset of the output signal after demodulation or the type of signal output. The pre-programming of the signal conditioning chip is carried out during its production process. Introducing the pre-programming process will greatly increase the complexity of the production process and raise the production cost.

[0109] To address the above technical problems, an embodiment of the present application provides a conditioning circuit for eddy current induced signals, as Figure 3 shown. The conditioning circuit 10 for eddy current induced signals is applied to an eddy current sensor. The conditioning circuit 10 for eddy current induced signals includes:[[]]

[0110] An oscillator module 101 for sending an excitation signal to the induction module 20 of the eddy current sensor. The excitation signal is used to trigger the generation of an oscillating electromagnetic field inside the induction module 20;

[0111] A demodulation module 102 for demodulating the induced signal output by the induction module 20 based on the excitation signal to obtain a demodulated signal carrying the displacement information of the measured object; The induced signal is used to indicate the displacement of the measured object detected under the oscillating electromagnetic field;

[0112] An output module 103 for amplifying the demodulated signal and outputting the amplified demodulated signal.

[0113] The induction module 20 refers to the part in the eddy current sensor that senses the displacement information of the object to be measured and thus generates an induction signal carrying the displacement information of the object to be measured. Among them, the displacement information of the object to be measured includes two types: angular displacement and linear displacement. When the types of displacement information are different, the internal structure of the induction module 20 will be different, but the working principle adopted is the eddy current effect, which is not specifically limited in this application.

[0114] Based on the eddy current effect, when the induction module 20 of the eddy current sensor measures the displacement information of the object to be measured, it needs to be in an oscillating electromagnetic field to generate an induction signal. In the embodiment of this 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 object to be measured, and the excitation coil is connected to 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 form an oscillating circuit to provide an excitation signal for the excitation coil so that it can generate an oscillating electromagnetic field. Among them, the oscillating circuit formed by the circuit in the oscillator module 101 and the excitation coil has various forms, such as an LC oscillating circuit and a quartz crystal oscillating circuit. The LC oscillating circuit includes various types, such as a parallel resonance oscillator and a series resonance oscillator, or a transformer-coupled oscillator and a three-point oscillator. Among them, the three-point oscillator includes a capacitor three-point oscillator and an inductor three-point oscillator.

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

[0117] An oscillator sub-circuit 1011, which is used to generate an oscillation signal;

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

[0119] In Figure 4In the circuit structure of the oscillator module 101 shown, the circuit is powered by a power supply. Utilizing the switching characteristics of the transistor T1 and combining capacitive and inductive elements, a stable oscillation loop is formed. When the oscillator sub-circuit 1011 operates, the transistor T1 periodically conducts and cuts off under the control of the base current, thereby generating an oscillation signal in the circuit. This oscillation signal is adjusted through two matching capacitors 1012 and the inductance of the excitation coil L to achieve a stable resonance frequency, 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 are the matching capacitors.

[0123] The demodulation module 102 is connected to the induction signal output end of the induction module 20, obtains the induction signal carrying the displacement information of the measured object, and performs demodulation processing on the induction 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, in order to obtain displacement information, the induction module 20 usually includes at least two groups of induction coils, and displacement information is obtained through at least two groups of induction signals generated in the at least two groups of induction coils.

[0124] In the application scenario of the eddy current sensor, the conditioning circuit needs to perform demodulation processing on all the induction signals generated in the induction module 20. For all the induction signals, the same demodulation idea can be adopted for demodulation. Therefore, the demodulation module 102 includes multiple repeated minimum demodulation parts, and each minimum demodulation part is used to demodulate a group of induction signals. In the subsequent explanation of the embodiments of the present application, taking the demodulation module 102 including only one minimum demodulation part as an example, the demodulation process of a group of induction signals is explained. In the actual application scenario, the corresponding number of minimum demodulation parts can be set in the demodulation module 102 according to the number of induction signals.

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

[0126] ;

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

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

[0129] ;

[0130] where is the amplitude of the induced voltage.

[0131] The demodulation module 102 needs to demodulate the induced signal to obtain the part carrying the displacement information of the object under test as the demodulated signal output. There are various ways for the demodulation module 102 to demodulate the induced signal , including but not limited to multiplicative demodulation, amplitude modulation (AM) demodulation, and harmonic frequency modulation (FM) demodulation. However, no matter which method is used, since it is necessary to retain the part of the induced signal carrying and filter out the 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 led out from the oscillator module 101 for demodulation of the induced signal.

[0132] Specifically, multiplicative demodulation mainly uses a reference signal (usually a sine wave) with the same frequency as the modulation signal to multiply the measured signal, so that the high-frequency components in the signal will be converted into higher-frequency components, and then the high-frequency components are filtered out through a low-pass filter to obtain the demodulated signal. In the application scenario of this embodiment, the modulation signal is , and the measured signal, that is, the induced signal, is . Using the excitation signal to multiply the induced signal , and then passing through a low-pass filter to obtain the demodulated signal.

[0133] Since the amplitude of the demodulated signal output by the demodulation module 102 is small, the signal is amplified by the output module 103 and then output to facilitate subsequent analysis of the displacement information based on the demodulated signal. The output module 103 uses components with amplification effects including but not limited to operational amplifiers and power amplifiers, and corresponding resistors, capacitors, etc. are set in the circuit to ensure stable output of the amplified signal.

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

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

[0136] For example, in one embodiment, the power supply module 104 includes a voltage regulation sub-module for converting the DC voltage provided by an external DC power supply into the working voltages of the oscillator module 101, the demodulation module 102, and the output module 103. Specifically, an LDO chip can be used in the voltage regulation sub-module, which supports a DC power input of 2.75V to 42V and can output a stable circuit working voltage.

[0137] The power supply module 104 also includes a circuit protection element and a filtering element. The circuit protection element can prevent abnormal conditions such as reverse connection, sudden change in power supply voltage, overvoltage, and overcurrent, and the filtering element can filter power supply noise.

[0138] In the circuit provided by the above embodiment, the circuit includes: an oscillator module for sending an excitation signal to the induction module of the eddy current sensor, where the excitation signal is used to trigger the generation of an oscillating electromagnetic field inside the induction module; a demodulation module for demodulating the induction signal output by the induction module based on the excitation signal to obtain a demodulation signal carrying the displacement information of the measured object; the induction signal is used to indicate the displacement of the measured object detected under the oscillating electromagnetic field; an output module for amplifying the demodulation signal and outputting the amplified demodulation signal. The demodulation of the induction signal is realized through the conditioning circuit provided by the application embodiment. The circuit structure is simple, without using a signal conditioning chip, which can effectively reduce the complexity of the sensor production process and reduce costs.

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

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

[0141] A second processing sub-circuit for detecting the low-frequency component in the envelope signal to obtain the demodulation signal.

[0142] Among them, the envelope signal refers to the curve of the signal amplitude changing with time. For the induction signal in terms of, since , the envelope of the induction signal is determined by , and its waveform diagram is as shown in Figure 6As shown. In practical applications, the induction signal is usually a complex waveform that has been modulated, which contains the information of the carrier signal (excitation signal) and the modulation signal. If direct detection is performed, it may be interfered by the carrier signal and other high-frequency components, resulting in a decrease in the quality of the demodulated signal.

[0143] The first processing sub-circuit is used to generate an envelope signal corresponding to the induction signal through 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 easy detection. Among them, the first processing sub-circuit can obtain the envelope signal corresponding to the induction signal by adding or multiplying the induction signal and the excitation signal.

[0144] For example, in one embodiment, the first processing sub-circuit includes:

[0145] An addition unit for superimposing the voltages of the induction signal and the excitation signal to obtain an envelope signal corresponding to the induction signal.

[0146] Given that the induction signal is , and the excitation signal is , since the amplitude of the induction voltage is usually in the order of several tens of millivolts, which is not conducive to the detection of subsequent circuits. Therefore, times the excitation coil signal is superimposed with the induction signal to obtain the envelope signal:

[0147] ;

[0148] As the main low-frequency component in the envelope signal, it carries the displacement information , which is detected by the second processing sub-circuit to obtain the demodulated signal .

[0149] In one of the embodiments, as Figure 7 shown, the addition unit includes:

[0150] A first resistor R1, the first end of the first resistor R1 is connected to the induction signal output end of the induction module 20;

[0151] A second resistor R2, the first end of the second resistor R2 is connected to the excitation signal output end of the oscillator module 101, and the second end is connected to the second end of the first resistor R1 to output an envelope signal corresponding to the induction signal.

[0152] In Figure 7In the shown addition circuit, the first resistor R1 and the second resistor R2 act as a voltage divider. They respectively reduce the voltages of the excitation signal and the induction signal to a voltage level suitable for addition. Then, based on the linear characteristics of the signals, these reduced voltages are directly added at the connection point of the first resistor R1 and the second resistor R2 to obtain an envelope signal. Among them, the magnitudes of the first resistor R1 and the second resistor R2 determine the magnitude of the

[0153] In the circuit provided by the above embodiment, signal demodulation is achieved by addition. Compared with the multiplication demodulation circuit, it is simpler. In particular, signal addition can be achieved by using only two resistors, which is beneficial to minimizing the overall structure of the conditioning circuit.

[0154] The second processing sub-circuit is mainly used for detection to detect the low-frequency components in the envelope signal. Common detection circuits have various forms and will not be elaborated here.

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

[0156] An amplification unit for amplifying the envelope signal corresponding to the induction signal and outputting the amplified envelope signal;

[0157] A detection unit for detecting the low-frequency components in the amplified envelope signal to obtain a demodulated signal.

[0158] By amplifying the envelope signal through the amplification unit, at this time, the envelope signal is , where is the amplification factor of the amplification unit. Correspondingly, the demodulated signal is . Detecting after amplification can effectively improve the detection effect of the detection unit on low-frequency components. Among them, the amplification unit uses components with amplification effects including but not limited to operational amplifiers and power amplifiers, and corresponding resistors, capacitors, etc. are set in the circuit to ensure stable output of the amplified signal. The detection unit can adopt the method of a low-pass filter to filter out high-frequency components and obtain low-frequency components. The low-pass filter includes but not limited to RC low-pass filters and LC low-pass filters.

[0159] In one of the embodiments, as Figure 8 shown, the amplification unit includes:

[0160] The first operational amplifier U1;

[0161] The third resistor R3, the first end of the third resistor R3 is connected to the output end of the first processing sub-circuit, and the second end is connected to the positive-phase input end of the first operational amplifier U1;

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

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

[0164] The detection unit includes:

[0165] The diode D1, the positive electrode of the diode D1 is connected to the output end of the amplification unit, and the negative electrode of the diode D1 outputs the demodulation signal;

[0166] The first capacitor C1, the first end of the first capacitor C1 is connected to the negative electrode of the diode D1, and the second end of the first capacitor C1 is grounded;

[0167] The sixth resistor R6, the first end of the sixth resistor R6 is connected to the negative electrode of the diode D1, and the second end of the sixth resistor R6 is grounded.

[0168] In Figure 8 In the circuit structure of the second processing sub-unit shown, the envelope signal is input to the positive-phase input end of the first operational amplifier U1 through the third resistor R3. The first operational amplifier U1 has a high gain and can amplify a tiny input signal to the required amplitude. The amplified signal is output from the output end of the first operational amplifier U1, providing sufficient signal strength for subsequent processing.

[0169] The amplified signal is detected by the diode D1. The diode D1 only allows forward current to pass through. Therefore, when the input signal is in the positive half-cycle, the diode conducts, and the current flows through the diode to the output end; when the input signal is in the negative half-cycle, the diode is cut off, and almost no current passes through. Thus, the diode D1 realizes the function of envelope detection, filtering out the high-frequency components in the input signal and only retaining the low-frequency components of the envelope signal. The detected signal passes through the low-pass filter composed 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 end through the sixth resistor R6, and then a pure demodulation signal can be obtained.

[0170] Figure 8In it, the fifth resistor R5 is the feedback resistor of the first operational amplifier U1, which determines the gain of the first operational amplifier U1. The inverting input terminal is grounded through the fourth resistor R4 to establish a stable reference voltage, usually 0V (grounded). This reference voltage is compared with the reference voltage at the non-inverting input terminal to determine the output signal of the amplifier. Grounding the fourth resistor R4 helps 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, for Figure 6 the induced signal shown, when demodulating by the addition demodulation method, an envelope signal as shown in Figure 9 and the demodulated signal output after detection can be obtained.

[0172] The form of the induced signal is not mentioned in the above embodiment and is defaulted to that the demodulation module 102 directly demodulates the single-ended induced signal. The differential signal has strong anti-interference ability, while the single-ended signal is easily interfered by external noise. Therefore, in the design of the eddy current sensor, a set of induction coils is set to generate a set of differential induced signals. The two signals represent the positive and negative polarities respectively. These two signals are equal in amplitude and have a phase difference of 180 degrees, such as SIN+ and SIN-. For a set of differential induced signals generated by the induction coils, they usually cannot be directly received by the circuit as a single-ended induced signal, but need to be converted by a conversion circuit to convert the differential induced signal into a single-ended induced signal.

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

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

[0175] The first processing sub-circuit is specifically used 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 be implemented in various ways, such as resistor voltage division, operational amplifier differential input, etc. These circuits can utilize the characteristics of the differential signal to convert it into a signal suitable for processing by the single-ended receiving circuit.

[0177] Among them, for resistor voltage division conversion: the positive and negative signals of the differential signal are voltage-divided through resistors, so that the positive and negative signals are synthesized into a single-ended signal at the output terminal after voltage division.

[0178] For operational amplifier conversion: the operational amplifier amplifies the difference between the two input signals according to the input differential signal by using its differential input characteristic, and then outputs the corresponding single-ended signal from the output terminal of the operational amplifier.

[0179] Taking 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. The first conversion sub-circuit includes:

[0180] A second operational amplifier U2;

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

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

[0183] A ninth resistor R9. The first end of the ninth resistor R9 is connected to the output terminal of the second operational amplifier U2, and the second end is connected to the inverting input terminal of the second operational amplifier U2;

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

[0185] In the Figure 10 shown circuit, 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 and is used to amplify and convert the input signal. It converts the received set of differential induction signals SIN+ and SIN- into a single-ended induction signal SIN and outputs it from the output terminal. 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 signals. The ninth resistor R9 is a feedback resistor and determines the gain of the second operational amplifier U2. The tenth resistor R10 is grounded and is used to connect the non-inverting input terminal of the second operational amplifier U2 to the ground to form a single-ended output.

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

[0187] The first end of the second capacitor C2 is connected to the positive power supply terminal of the second operational amplifier U2, and the second end is grounded;

[0188] The first end of the third capacitor C3 is connected to the negative power supply terminal of the second operational amplifier U2, and the 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 pins to stabilize the input power supply voltage.

[0190] Through the processing of the induction signal by the demodulation module 102, the part of the induction signal carrying the displacement information of the object to be measured has been extracted. However, the amplitude of the obtained demodulation signal is usually about several hundred millivolts, and its quality and usability are limited. If it is necessary to obtain the displacement information from the demodulation signal , it is necessary to improve the quality and usability of the demodulation signal, including but not limited to bias arrangement, linearization processing, amplitude adjustment and other processing. In the embodiment of the present application, the output module 103 amplifies the demodulation signal to output an available demodulation signal. Both the demodulation signal and the amplified demodulation signal are single-ended induction signals. In some embodiments, in order to ensure the quality of the amplified demodulation signal received in the subsequent module, it needs to be converted into a differential signal for transmission.

[0191] Correspondingly, a single-ended induction signal needs to be converted into a group of differential signals. The methods of converting a single-ended signal into a differential signal are mainly divided into two types: active device conversion and passive device conversion. Active device conversion uses an amplifier to convert a single-ended signal into a differential signal. The single-ended signal is input to one input terminal of the amplifier, and a common-mode signal and an in-phase signal with an original amplitude of 1 / 2 are respectively output through the common-phase and in-phase output terminals of the amplifier. Passive device conversion uses a balun or a transformer to realize the conversion of a single-ended signal into a differential signal. These devices can utilize the characteristics of the transformer to convert an AC signal into a differential signal with opposite phases and the same amplitude. The single-ended signal is input to one input terminal of the balun or the transformer, and a pair of differential signals are output through its internal structure and electromagnetic induction principle.

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

[0193] A second conversion sub-circuit for amplifying the demodulation signal and converting the amplified signal into a first target sub-signal;

[0194] A third conversion sub-circuit for amplifying the demodulation signal and converting 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] Among them, the amplification processing of the demodulation signal includes amplitude adjustment and adding a DC bias. The single-ended signal is converted into a group 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 for adjusting the DC bias of the demodulation signal and outputting the adjusted demodulation signal;

[0198] A second adjustment unit, configured to amplify the adjusted demodulation signal and output a first target sub-signal.

[0199] As Figure 11 shown, the first adjustment unit includes:

[0200] An eleventh resistor R11, with the first end of the eleventh resistor R11 connected to the reference voltage Vref;

[0201] A twelfth resistor R12, with the first end of the twelfth resistor R12 connected to the second end of the eleventh resistor R11 and the second end grounded;

[0202] A fourth capacitor C4, with the first end of the fourth capacitor C4 connected to the output end of the demodulation module, and the second end connected to the second end of the eleventh resistor R11, the first end of the twelfth resistor R12, and the input end of the second adjustment unit.

[0203] The second adjustment unit includes:

[0204] A third operational amplifier U3, with the non-inverting input terminal of the third operational amplifier U3 connected to the output end of the first adjustment unit;

[0205] A thirteenth resistor R13, with the first end of the thirteenth resistor R13 connected to the output end of the third operational amplifier U3 and the second end connected to the inverting input terminal of the third operational amplifier U3;

[0206] A fourteenth resistor R14, with the first end of the fourteenth resistor R14 connected to the inverting input terminal of the third operational amplifier U3;

[0207] A fifth capacitor C5, with the first end of the fifth capacitor C5 connected to the second end of the fourteenth resistor R14 and the second end grounded.

[0208] The second adjustment unit further includes:

[0209] A sixth capacitor C6, with the first end of the sixth capacitor C6 connected to the positive power supply terminal of the third operational amplifier U3 and the second end grounded;

[0210] A seventh capacitor C7, with the first end of the seventh capacitor C7 connected to the output end of the third operational amplifier U3 and the second end grounded.

[0211] In Figure 11In the shown circuit structure, the third operational amplifier U3 is the core component of the circuit. It receives the single-ended induction signal SIN (demodulation signal) as input, and after internal amplification and filtering processing, outputs the differential signal SIN+ (the first target sub-signal). The eleventh resistor R11 and the twelfth resistor R12 are resistors used to add DC bias. Adjusting the ratio of the eleventh resistor R11 and the twelfth resistor R12 will change the DC level at the input end and the DC component at 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 form the feedback loop of the AC amplification circuit. The AC amplification factor is (1 + R13 / R14), and the DC amplification factor is 1. The sixth capacitor C6 is a bypass capacitor. The seventh capacitor C7 is used to filter out the high-frequency noise in the output signal and improve the purity of the output signal.

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

[0213] In one of the embodiments, as Figure 12 shown, the third conversion sub-circuit includes:

[0214] The fourth operational amplifier U4;

[0215] The fifteenth resistor R15, the first end of the fifteenth resistor R15 inputs the demodulation signal, and the second end is connected to the inverting input terminal of the fourth operational amplifier U4;

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

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

[0218] The eighteenth resistor R18, the first end of the eighteenth resistor R18 is connected to the output terminal of the fourth operational amplifier U4, and the second end is connected to the inverting input terminal of the fourth operational amplifier U4.

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

[0220] The first end of the eighth capacitor C8 is connected to the output terminal of the demodulation module, and the second end is connected to the first end of the fifteenth resistor R15;

[0221] The second terminal of the fifteenth resistor R15 is connected to the inverting input terminal of the fourth operational amplifier U4;

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

[0223] In Figure 12 In the circuit shown, 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 induction 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 terminal of the operational amplifier can be changed, thereby realizing the adjustment of the DC bias of the output signal.

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

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

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

[0228] 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 to provide a stable reference voltage Vref.

[0229] In one embodiment, when two sets of induction coils are included in the induction module 20, after Figure 11 and Figure 12 the processing of the circuit in, when the DC bias of the output signal is set to VDD / 2 (2.5V), the two sets of differential signals output by the output module 103 are as Figure 13 shown. In one embodiment, the output module 103 outputs the two sets of differential signals to the MCU, and the four-channel ADC ports on the MCU receive the four-channel differential signals and convert them into digital signals. After parsing, the four-channel differential input signals can be converted into two single-ended signals:

[0230] ;

[0231] ;

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

[0233] ;

[0234] This information can be used in various detection scenarios such as motor position detection and motor speed detection.

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

[0236] Specifically, in one embodiment, as Figure 14 shown, an eddy current sensor for measuring rotational speed includes a rotor, two sets of induction coils, an excitation coil, and a conditioning circuit. Among them, the induction coil, 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 consists of a coil part and a circuit part. The coil part is circular, the lower half is connected to the circuit board, and there is a regular circular hollow in the middle. The excitation coil and the induction coil (distributed in a closed whole circle).

[0237] The excitation coil is distributed in the outermost circle of the coil part. It is a complete multi-turn regular circular coil, and a section is led out from each of the head and the tail and connected to the oscillator module 101 of the circuit. The induction coil is distributed inside the excitation coil, and the outermost periphery is close to the innermost turn of the excitation coil. Such a design can make the magnetic field generated by the excitation coil change uniformly and at a high frequency, and a uniform induced electromotive force is generated on the induction coil. The induction coil is composed of two sets of coils with specific shapes that do not intersect each other and have a phase difference of 90°. The two sets of induction coils are connected to the demodulation module 102 in the conditioning circuit in a differential manner, providing four-way differential signal inputs.

[0238] The metal rotor is fixed on the motor shaft, and the sector blades on the rotor just cover the entire induction coil. The number of poles of the sector blades corresponds to the number of pole pairs designed for the induction coil. While the motor is rotating, the rotor rotates above the induction coil at the same speed. Under the influence of the alternating magnetic field (3 - 5 MHz) of the excitation coil, eddy currents are induced on the rotor surface. The induced magnetic field of the eddy currents is opposite to the excitation magnetic field, canceling out a part of the alternating magnetic field (when the rotor rotates, an electromagnetic field opposite to the excitation magnetic field will be generated on the surface, weakening the excitation magnetic field of the part of the induction coil covered by the rotor). As the rotor rotates, the output of the induction coil changes in a SIN-shaped signal under the action of the eddy currents, and the change frequency is equal to the product of the motor rotation frequency and the number of rotor pole pairs. Therefore, when the sensor and the motor are working simultaneously, the signal output by the induction coil can be regarded as a SIN-shaped signal modulated by a high-frequency signal.

[0239] An embodiment of the present application further provides a displacement measuring device, and the device includes the above-mentioned eddy current sensor.

[0240] An embodiment of the present application further provides a vehicle, and the vehicle includes the above-mentioned 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 comprises: An oscillator module, used for sending an excitation signal to the sensing module of the eddy current sensor, wherein the excitation signal is used for triggering the generation of an oscillating electromagnetic field inside the sensing module; A demodulation module, configured to demodulate the sensing signal output by the sensing module based on the excitation signal to obtain a demodulation signal carrying displacement information of the object under test; the sensing signal is used to indicate the displacement of the object under test 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, characterized in that The demodulation module comprises: A first processing sub-circuit, configured to generate an envelope signal corresponding to the sensing signal based on the sensing signal and the excitation 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 subcircuit comprises: The adding unit is used to superimpose the voltage of the sensing signal and the voltage of the excitation signal to obtain an envelope signal corresponding to the sensing signal.

4. The circuit according to claim 3, characterized in that The adding unit comprises: 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, and 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.

5. The circuit according to claim 2, characterized in that The second processing sub-circuit comprises: an amplifying unit, used to amplify the 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.

6. The circuit according to claim 5, characterized in that The amplification unit comprises: 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.

7. The circuit according to claim 5, characterized in that The detection unit comprises: 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.

8. 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 also includes a first conversion subcircuit; The first conversion subcircuit is used to combine the group 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.

9. The circuit according to claim 8, characterized in that The first conversion subcircuit comprises: a second operational amplifier; a seventh resistor, wherein a first end of the seventh resistor is input with a first differential signal in the group of differential sensing signals, and a second end of the seventh resistor is connected to a non-inverting input end 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 end 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 end of the second operational amplifier, and a second end of the tenth resistor is grounded.

10. The circuit according to claim 9, 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.

11. The circuit according to claim 1, characterized in that The output module comprises: A second conversion sub-circuit, used for amplifying the demodulated signal and converting the amplified signal into a first target sub-signal; The third conversion sub-circuit is used to amplify the demodulated signal and convert the adjusted signal into a second target sub-signal, wherein the first target sub-signal and the second target sub-signal are a group of differential signals.

12. The circuit according to claim 11, characterized in that The second conversion sub-circuit comprises: A first adjustment unit, used for adjusting a DC bias of the demodulated signal and outputting an adjusted demodulated signal; The second adjustment unit is used to amplify the adjusted demodulated signal and output the first target sub-signal.

13. The circuit according to claim 12, characterized in that The first adjustment unit comprises: 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.

14. The circuit according to claim 12, 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 a second end of the thirteenth resistor; A fifth capacitor, wherein a first end of the fifth resistor is connected to a second end of the fourteenth resistor, and a second end is grounded.

15. The circuit according to claim 14, 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.

16. The circuit according to claim 11, characterized in that The third conversion sub-circuit comprises: a fourth operational amplifier; a fifteenth resistor, a first end of which is input with the demodulated signal, and a second end of which is connected with the inverting input end of the fourth operational amplifier; a sixteenth resistor, a first end of the sixteenth resistor being connected to a reference voltage, and a second end of the sixteenth resistor being connected to a non-inverting input end of the fourth operational amplifier; A seventeenth resistor, 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.

17. The circuit according to claim 16, 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 end 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 of the ninth capacitor is grounded.

18. The circuit according to claim 1, characterized in that The induction module includes an excitation coil, and the oscillator module includes: An oscillator subcircuit, the oscillator subcircuit is used to generate an oscillation signal; Two matching capacitors are used to form a resonant circuit with the excitation coil to adjust the resonant frequency of the oscillation signal to obtain the excitation signal.

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

20. The circuit according to claim 19, characterized in that The power module comprises: 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.

21. An eddy current sensor, characterized in that: The eddy current sensor comprises a sensing module and a conditioning circuit for eddy current sensing signals as described in any one of claims 1 to 20.

22. A displacement measuring device, characterized in that: The device comprises the eddy current sensor as claimed in claim 21.

23. A vehicle, characterized in that: The vehicle includes the eddy current sensor as claimed in claim 21.

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