Linear variable differential transformer sensor measurement correction method and signal conditioning device

Abstract

The present application discloses a linear variable differential transformer sensor measurement and correction method and a signal conditioning device, and relates to the field of linear variable differential transformer sensors. The method includes obtaining a compensation fitting coefficient, obtaining an effective value signal, a phase difference signal, and an effective value signal of an induced voltage signal when using a linear variable differential transformer sensor to measure the displacement of an object to be measured, and performing temperature drift compensation based on the effective value signal value, the phase difference signal value, and the effective value signal value of the induced voltage signal of the object to be measured in combination with the compensation fitting coefficient to obtain a corrected displacement measurement value. The present application can compensate for the displacement data drift caused by the temperature of the linear variable differential transformer sensor, and reduce the influence of the temperature drift on the output of the linear variable differential transformer sensor.

Description

Technical Field

[0001] The present application relates to the field of linear variable differential transformer sensors, and in particular to a linear variable differential transformer sensor measurement and correction method and a signal conditioning device. Background Art

[0002] LVDT (Linear Variable Differential Transformer) sensor is a commonly used displacement measurement sensor that can output linear displacement measurement results through DC analog or digital communication interface. It has the advantages of high sensitivity, simple structure, and long service life. LVDT sensors are widely used in various industrial control, scientific research and measurement fields.

[0003] The sensing part of the LVDT sensor is mainly composed of the primary coil, secondary coil, iron core and other components. The common LVDT sensor contains two secondary coils connected in series in reverse. When the primary coil is supplied with an alternating voltage, the secondary coil will generate an induced voltage. When the iron core in the sensing part moves with the object being measured, the induced voltages of the two secondary coils will change differently. By analyzing and processing the value of the induced voltage, the displacement of the iron core can be inferred.

[0004] However, in the development of actual products, LVDT sensors are often affected by factors such as ambient temperature or their own temperature rise, causing the results to shift. Therefore, it is necessary to correct the displacement measurement results obtained. Summary of the invention

[0005] The purpose of the present application is to provide a linear variable differential transformer sensor measurement correction method and a signal conditioning device, which can compensate for the displacement data drift caused by the linear variable differential transformer sensor under the influence of temperature and reduce the influence of temperature drift on the output of the linear variable differential transformer sensor.

[0006] To achieve the above objectives, this application provides the following solutions.

[0007] In a first aspect, the present application provides a linear variable differential transformer sensor measurement and correction method, including: obtaining a compensation fitting coefficient; obtaining an effective value signal, a phase difference signal and an effective value signal of an induced voltage signal when the linear variable differential transformer sensor is used to measure the displacement of an object to be measured; the phase difference signal is a phase difference signal between an excitation voltage signal and an excitation source signal generated by a linear variable differential transformer sensor signal conditioning device when stimulating a primary coil in the linear variable differential transformer sensor; and performing temperature drift compensation using the compensation fitting coefficient according to the effective value signal value, the phase difference signal value and the effective value signal value of the excitation voltage signal of the object to be measured to obtain a corrected displacement measurement value.

[0008] In a second aspect, the present application provides a linear variable differential transformer sensor signal conditioning device, comprising: a coil excitation circuit, a first acquisition circuit, a second acquisition circuit, a third acquisition circuit and a data processing circuit. The coil excitation circuit is respectively connected to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor; the coil excitation circuit is used to generate an excitation source signal and an excitation voltage signal, and output the excitation voltage signal to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor, respectively, and output the excitation source signal to the second acquisition circuit. The first acquisition circuit is connected to the data processing circuit; the first acquisition circuit is used to obtain an effective value signal of the excitation voltage signal and output it to the data processing circuit. The second acquisition circuit is connected to the data processing circuit; the second acquisition circuit is used to obtain a phase difference signal between the excitation voltage signal and the excitation source signal, and output it to the data processing circuit. The third acquisition circuit is respectively connected to the secondary coil in the linear variable differential transformer sensor and the data processing circuit; the third acquisition circuit is used to collect the induced voltage signal generated by the secondary coil when the linear variable differential transformer sensor measures the displacement of the object to be measured, and output the effective value signal of the induced voltage signal to the data processing circuit. The data processing circuit is used to perform temperature drift compensation according to the effective value signal of the excitation voltage signal, the phase difference signal and the effective value signal of the induced voltage signal by using the above-mentioned linear variable differential transformer sensor measurement correction method to obtain a corrected displacement measurement value.

[0009] According to the specific embodiments provided in this application, this application discloses the following technical effects.

[0010] The present application provides a linear variable differential transformer sensor measurement and correction method and a signal conditioning device. By measuring the phase difference signal between the excitation voltage signal and the excitation source signal generated by the linear variable differential transformer sensor signal conditioning device when stimulating the primary coil in the linear variable differential transformer sensor, the displacement measured by the linear variable differential transformer sensor is compensated for temperature drift in combination with the compensation fitting coefficient, thereby compensating for the displacement data drift caused by the temperature of the linear variable differential transformer sensor and reducing the temperature drift influence of the linear variable differential transformer sensor output. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] Figure 1A schematic flow chart of a linear variable differential transformer sensor measurement and correction method provided in one embodiment of the present application.

[0013] Figure 2 A schematic diagram of the circuit composition of a linear variable differential transformer sensor signal conditioning device provided in one embodiment of the present application.

[0014] Figure 3 A schematic diagram of the coil excitation circuit principle provided in one embodiment of the present application.

[0015] Figure 4 A schematic diagram of the principle of a first acquisition circuit provided in an embodiment of the present application.

[0016] Figure 5 This is a schematic diagram of the principle of a second acquisition circuit provided in one embodiment of the present application.

[0017] Figure 6 This is a schematic diagram of the principle of a third acquisition circuit provided in an embodiment of the present application.

[0018] Figure 7 A schematic diagram of a data processing circuit provided in one embodiment of the present application.

[0019] Figure 8 A schematic diagram of a coil excitation circuit design provided in one embodiment of the present application.

[0020] Fig. 9 A schematic diagram of a first acquisition circuit design provided in an embodiment of the present application.

[0021] Fig.10 A schematic diagram of a second acquisition circuit design provided in an embodiment of the present application.

[0022] Fig.11 A schematic diagram of a third acquisition circuit design provided in an embodiment of the present application.

[0023] Fig.12 A schematic diagram of a data processing circuit design provided in one embodiment of the present application. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0026] In an exemplary embodiment, Figure 1 As shown, a linear variable differential transformer sensor measurement and correction method is provided, including the following steps 101 to 103.

[0027] Step 101: Obtain compensation fitting coefficients.

[0028] Step 102: Obtaining an effective value signal of an excitation voltage signal, a phase difference signal, and an effective value signal of an induced voltage signal when the displacement of the object to be measured is measured using a linear variable differential transformer sensor. The phase difference signal is a phase difference signal between an excitation voltage signal and an excitation source signal generated by a linear variable differential transformer sensor signal conditioning device when the primary coil in the linear variable differential transformer sensor is excited.

[0029] Step 103: According to the effective value signal value of the excitation voltage signal, the phase difference signal value and the effective value signal value of the induced voltage signal of the object to be measured, the compensation fitting coefficient is used to perform temperature drift compensation to obtain a corrected displacement measurement value.

[0030] By implementing the above steps 101 to 103, the phase difference signal between the excitation voltage signal and the excitation source signal generated by the linear variable differential transformer sensor signal conditioning device when exciting the primary coil in the linear variable differential transformer sensor is measured, and the displacement measured by the linear variable differential transformer sensor is compensated for by temperature drift in combination with the compensation fitting coefficient, thereby compensating for the displacement data drift caused by the temperature of the linear variable differential transformer sensor and reducing the influence of the temperature drift on the output of the linear variable differential transformer sensor.

[0031] In another exemplary embodiment of the present application, in order to clarify the determination method of the compensation fitting coefficient, the above step 101 is replaced by the following steps 201 to 206.

[0032] Step 201: obtaining effective value signals of an excitation voltage signal, a phase difference signal and an effective value signal of an induced voltage signal when a linear variable differential transformer sensor is used to measure displacements of gauge blocks of different lengths at a preset ambient temperature; the length of the gauge block is equal to the actual displacement.

[0033] Step 202: Calculate the average value of the phase difference signal values ​​of all gauge blocks at a preset ambient temperature.

[0034] Step 203: Fitting the corresponding relationship between the ratio at a preset ambient temperature and the length of the gauge block to obtain a first calibration fitting relationship and a first calibration fitting coefficient and a second calibration fitting coefficient in the first calibration fitting relationship. The ratio is the ratio of the effective value signal value of the induced voltage signal to the effective value signal value of the excitation voltage signal.

[0035] Step 204: Change the preset ambient temperature multiple times. After each change of the preset ambient temperature, return to the step of "obtaining the effective value signal of the excitation voltage signal, the phase difference signal and the effective value signal of the induced voltage signal when measuring the displacement of blocks of different lengths using the linear variable differential transformer sensor at the preset ambient temperature" to obtain the average value of the phase difference signal value at multiple different preset ambient temperatures, the first calibration fitting coefficient and the second calibration fitting coefficient.

[0036] Step 205: Fit the correspondence between the average value of the phase difference signal values ​​under multiple different preset ambient temperatures and the first calibration fitting coefficient, obtain the second calibration fitting relationship and the third calibration fitting coefficient and the fourth calibration fitting coefficient in the second calibration fitting relationship, and fit the correspondence between the average value of the phase difference signal values ​​under multiple different preset ambient temperatures and the second calibration fitting coefficient, obtain the third calibration fitting relationship and the fifth calibration fitting coefficient and the sixth calibration fitting coefficient in the third calibration fitting relationship.

[0037] Step 206: Determine the third calibration fitting coefficient, the fourth calibration fitting coefficient, the fifth calibration fitting coefficient and the sixth calibration fitting coefficient as compensation fitting coefficients.

[0038] In another exemplary embodiment of the present application, on the basis of steps 201 to 206, the detailed implementation process of step 103 is as follows: steps 301 to 303.

[0039] Step 301: According to the phase difference signal value of the object to be measured, the third calibration fitting coefficient and the fourth calibration fitting coefficient, the value of the first calibration fitting coefficient of the object to be measured is obtained by using the second calibration fitting relationship.

[0040] Step 302: According to the phase difference signal value of the object to be measured, the fifth calibration fitting coefficient and the sixth calibration fitting coefficient, the value of the second calibration fitting coefficient of the object to be measured is obtained by using the third calibration fitting relationship.

[0041] Step 303: Obtain a corrected displacement measurement value using a first calibration fitting relationship according to the phase difference signal value, the effective value signal value of the induced voltage signal, the first calibration fitting coefficient value of the object to be measured and the second calibration fitting coefficient value of the object to be measured.

[0042] In another exemplary embodiment of the present application, a specific form of the first calibration fitting relationship obtained in step 203 is as follows.

[0043] Si=E1×(C1i / A1i)+F1.

[0044] Wherein, Si is the length of the gauge block at the i-th measurement at the preset ambient temperature, E1 is the first calibration fitting coefficient, C1i is the effective value signal value of the induced voltage signal at the i-th measurement at the preset ambient temperature, A1i is the effective value signal value of the excitation voltage signal at the i-th measurement at the preset ambient temperature, and F1 is the second calibration fitting coefficient.

[0045] A specific form of the second calibration fitting relationship obtained in step 205 is as follows.

[0046] Ej=H1×Dj+H2.

[0047] Wherein, Ej is the first calibration fitting coefficient at the j-th preset ambient temperature, Dj is the average value of the phase difference signal value at the j-th preset ambient temperature, H1 is the third calibration fitting coefficient, and H2 is the fourth calibration fitting coefficient.

[0048] A specific form of the third calibration fitting relationship obtained in step 205 is as follows.

[0049] Fj=H3×Dj+H4.

[0050] Wherein, Fj is the second calibration fitting coefficient at the j-th preset ambient temperature, Dj is the average value of the phase difference signal value at the j-th preset ambient temperature, H3 is the fifth calibration fitting coefficient, and H4 is the sixth calibration fitting coefficient.

[0051] The effective value signal of the excitation voltage signal is simplified using signal V3, the phase difference signal is simplified using signal V4, and the effective value signal of the induced voltage signal is simplified using signal V6. Based on this, a more specific implementation process is used below to illustrate the method for determining the compensation fitting coefficient and the method for displacement correction.

[0052] Taking the use of a standard gauge block as an example, the method for determining the compensation fitting coefficient is as follows: Steps 1.1 to 1.6. The standard gauge block is a standard end face gauge without scale.

[0053] Step 1.1: When the ambient temperature is t1, use an LVDT sensor to measure the standard gauge block, the length of the gauge block is S1, and obtain the values ​​of signal V3, signal V4 and signal V6 when the ambient temperature is t1, which are recorded as A11, B11 and C11 respectively.

[0054] Step 1.2: Keeping the ambient temperature unchanged, replace the standard gauge block and repeat the measurement. The lengths of the standard gauge blocks are S2, S3, …, Sm respectively. Obtain the values ​​of signal V3, signal V4 and signal V6, which are recorded as A12, B12, C12, A13, B13, C13, …, A1m, B1m, C1m.

[0055] Step 1.3: Calculate the average value of signal V4, denoted as D1, that is , i ranges from 1 to m, m represents the number of measurements, and B1i is the value of the phase difference signal at the i-th measurement under the preset ambient temperature.

[0056] Step 1.4: Use the least squares method or other linear fitting algorithms to fit the corresponding relationship between the ratio of the numerical value of signal V6 to the numerical value of signal V3 and the length of the gauge block, and obtain the first calibration fitting coefficient and the second calibration fitting coefficient, denoted as E1 and F1, that is, Si=E1×(C1i / A1i)+F1, where i ranges from 1 to m.

[0057] Step 1.5: Change the ambient temperature to t2, t3, ..., tn. After each change of the ambient temperature, repeat steps 1.1, 1.2, 1.3 and 1.4 to obtain the average value of the signal V4, the first calibration fitting coefficient and the second calibration fitting coefficient, which are D2, E2, F2, D3, E3, F3, ..., Dn, En, Fn, respectively. Where n represents the number of ambient temperatures.

[0058] Step 1.6: Use the least squares method or other linear fitting algorithms to fit the average value of the signal V4 with the first calibrated fitting coefficient and the second calibrated fitting coefficient to obtain the compensation fitting coefficients, which are recorded as H1, H2, H3, and H4, that is, Ej=H1×Dj+H2, Fj=H3×Dj+H4, and the value range of j is 1 to n.

[0059] The displacement correction method is shown in steps 2.1 to 2.4 below.

[0060] Step 2.1: Read the compensation fitting coefficients H1, H2, H3, and H4.

[0061] Step 2.2: Obtain the measured values ​​of signal V3, signal V4 and signal V6, recorded as At, Bt, Ct.

[0062] Step 2.3: Use the signal measurement values ​​and the compensation fitting coefficients to calculate the calibration fitting coefficients Et and Ft, that is, Et=H1×Bt+H2, Ft=H3×Bt+H4.

[0063] Step 2.4: Use the calibration fitting coefficient to calculate the corrected displacement measurement value St, that is, St = Et × (Ct / At) + Ft.

[0064] The coil part of the LVDT sensor will generate heat due to the influence of the ambient temperature and the thermal effect of its own current. The inductance in the primary coil of the LVDT sensor includes self-inductance and mutual inductance, among which the mutual inductance of the primary coil is less affected by the position of the magnetic core in the sensor measurement, that is, when the environmental conditions remain unchanged, the change of the measured object will basically not affect the inductance of the primary coil. The resistance in the primary coil will not change due to the change of the measured object. Since the resistance and inductance in the primary coil have different temperature change curves, the phase angle of the overall impedance will change with the temperature change. Then, the temperature drift of the sensor can be evaluated by the change of the signal phase in the signal conditioning circuit, and the temperature drift compensation can be performed. The present application indirectly compensates for the data drift caused by the temperature of the LVDT sensor by constructing the excitation source signal and the excitation voltage signal of the primary coil excitation in the signal conditioning device, and measuring the phase difference change between the excitation source signal and the excitation voltage signal, so as to obtain the displacement measurement result of the LVDT sensor with compensation characteristics, and reduce the influence of the temperature drift of the LVDT sensor output. At present, the LVDT sensors on the market do not have or do not express the function of temperature drift compensation.

[0065] Based on the same inventive concept, the embodiment of the present application also provides a linear variable differential transformer sensor signal conditioning device, such as Figure 2 As shown, it includes: a coil excitation circuit, a first acquisition circuit, a second acquisition circuit, a third acquisition circuit and a data processing circuit. The coil excitation circuit is respectively connected to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor; the first acquisition circuit is connected to the data processing circuit; the second acquisition circuit is connected to the data processing circuit; the third acquisition circuit is respectively connected to the secondary coil in the linear variable differential transformer sensor and the data processing circuit.

[0066] The coil excitation circuit is used to generate an excitation source signal and an excitation voltage signal, and output the excitation voltage signal to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor respectively, and output the excitation source signal to the second acquisition circuit. The first acquisition circuit is used to obtain the effective value signal of the excitation voltage signal and output it to the data processing circuit. The second acquisition circuit is used to obtain the phase difference signal between the excitation voltage signal and the excitation source signal and output it to the data processing circuit. The third acquisition circuit is used to collect the induced voltage signal generated by the secondary coil when the linear variable differential transformer sensor measures the displacement of the object to be measured, and output the effective value signal of the induced voltage signal to the data processing circuit. The data processing circuit is used to perform temperature drift compensation according to the effective value signal of the excitation voltage signal, the phase difference signal and the effective value signal of the induced voltage signal using the above-mentioned linear variable differential transformer sensor measurement correction method to obtain a corrected displacement measurement value.

[0067] In order to compensate for temperature drift, the existing method needs to measure the temperature value. In terms of hardware design, it is necessary to install a temperature measuring device on the LVDT sensor coil, and an electric wire line needs to be added between the coil and the signal conditioning circuit to transmit the temperature signal. This will increase the size of the sensing part of the LVDT sensor, which is not convenient for product miniaturization design. The device of the present application does not need to increase the hardware settings of the sensing part of the LVDT sensor, but measures the signal on the original transmission line. While increasing the function, the original size of the sensing part of the LVDT sensor is maintained.

[0068] As an optional implementation, the coil excitation circuit is responsible for exciting the primary coil, such as Figure 3 As shown, the coil excitation circuit includes: a waveform generating unit and a first following unit. The first following unit includes an operational amplifier and a current limiting resistor; the waveform generating unit is connected to the operational amplifier; the operational amplifier is respectively connected to the current limiting resistor and the second acquisition circuit, and the current limiting resistor is also connected to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor. The waveform generating unit is used to generate a sine wave signal and output it to the operational amplifier; the operational amplifier is used to perform voltage following on the sine wave signal, obtain an excitation source signal, and output the excitation source signal to the current limiting resistor and the second acquisition circuit respectively; the current limiting resistor is used to limit the primary coil current, adjust the signal phase, obtain an excitation voltage signal, and output the excitation voltage signal to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor respectively.

[0069] Reference Figure 3 The coil excitation circuit is mainly composed of a waveform generating unit and a first following unit. The waveform generating unit is composed of a waveform generating chip and related adjustment elements such as resistors and capacitors, and generates a sine wave signal to output to the first following unit. The first following unit is a voltage following circuit composed of an operational amplifier and a current limiting resistor, which adjusts the line impedance characteristics and outputs a sine wave signal to the primary coil. The sampling point of the excitation voltage signal V1 is the output end of the current limiting resistor, and the sampling point of the excitation source signal V2 is the output end of the operational amplifier.

[0070] Reference Figure 8, using actual circuits to illustrate the working principle of the coil excitation circuit. The waveform generating unit consists of chip U1, resistor R102, resistor R103, resistor R104, resistor R105 and capacitor C101. Chip U1 is a waveform generator, model ICL8038, which can generate a sine wave signal. Resistors R102, R103 and capacitor C101 are used to adjust the frequency of the output sine wave. Resistors R104 and R105 are used to adjust the waveform distortion rate. The first follower unit consists of chip U2 and resistor R101. Chip U2 is an operational amplifier, model OPA228, which can realize the voltage following function. Resistor R101 is a current limiting resistor that limits the current of the primary coil.

[0071] As an optional implementation, Figure 4 As shown, the first acquisition circuit includes: a first effective value conversion unit and a second following unit. The first effective value conversion unit is connected to the coil excitation circuit and the second following unit respectively; the second following unit is connected to the data processing circuit. The first effective value conversion unit is used to reduce the ratio of the excitation voltage signal generated by the coil excitation circuit, and convert the reduced-ratio excitation voltage signal into an effective value signal in the form of a DC voltage signal, and then output it to the second following unit. The second following unit is used to perform voltage following on the effective value signal of the excitation voltage signal, while adjusting the line impedance characteristics, and output the effective value signal of the excitation voltage signal to the data processing circuit.

[0072] Reference Figure 4 The first acquisition circuit is composed of a first effective value conversion unit and a second follower unit. The first effective value conversion unit is composed of an effective value conversion chip and related adjustment elements such as resistors and capacitors. It reduces the proportion of the excitation voltage signal, converts it into an effective value signal in the form of a DC voltage signal, and outputs it to the second follower unit. The second follower unit is a voltage follower circuit composed of an operational amplifier and a current limiting resistor, which adjusts the line impedance characteristics and outputs the effective value signal of the excitation voltage signal to the data processing circuit.

[0073] Reference Fig. 9 , the working principle of the first acquisition circuit is explained with an actual circuit. The first effective value conversion unit is composed of chip U3, resistor R201, resistor R202, capacitor C201 and capacitor C202. Chip U3 is an effective value converter, model LTC1968, which can obtain the effective value of the input signal and output it in the form of a DC voltage signal. Resistors R201 and R202 are used to adjust the input signal amplitude of chip U3. Capacitor C201 is used to couple the input signal to prevent DC or low-frequency signal input. Capacitor C202 is used to output the signal smoothly. The second follower unit is composed of chip U4 and resistor R203. Chip U4 is an operational amplifier, model OPA228, which can realize the voltage following function. Resistor R203 is a current limiting resistor that limits the output signal current amplitude.

[0074] As an optional implementation, Figure 5 As shown, the second acquisition circuit includes: a phase difference measurement unit and a third following unit. The phase difference measurement unit is connected to the coil excitation circuit and the third following unit respectively; the third following unit is connected to the data processing circuit. The phase difference measurement unit is used to obtain a phase difference signal between the excitation voltage signal and the excitation source signal, and output the phase difference signal to the third following unit in the form of a DC voltage signal. The third following unit is used to perform voltage following on the phase difference signal in the form of a DC voltage signal, while adjusting the line impedance characteristics, and output the phase difference signal in the form of a DC voltage signal to the data processing circuit.

[0075] Figure 5 The second acquisition circuit shown is composed of a phase difference measurement unit and a third follower unit. The phase difference measurement unit is composed of a phase detection chip and related adjustment elements such as resistors and capacitors. It converts the phase difference between the excitation voltage signal and the excitation source signal in the form of a DC voltage signal and outputs it to the third follower unit. The third follower unit is a voltage follower circuit composed of an operational amplifier and a current limiting resistor, which adjusts the line impedance characteristics and outputs the phase difference signal to the data processing circuit.

[0076] Reference Fig.10 , the working principle of the second acquisition circuit is explained with an actual circuit. The phase difference measurement unit is composed of chip U5, resistor R301, resistor R302, resistor R303, resistor R304, resistor R305, resistor R306, capacitor C301, capacitor C302, capacitor C303, capacitor C304, capacitor C305 and capacitor C306. Chip U5 is a phase detector, model AD8302, which can obtain the phase difference of two input signals and output it in the form of a DC voltage signal. Resistors R301, R302, R303, R304, R305 and R306 are used to adjust the input signal amplitude of chip U5. Capacitors C301, C302, C303 and C304 are used to couple input signals to prevent DC or low-frequency signal input. Capacitors C305 and C306 provide low-pass filtering for the output signal. The third follower unit is composed of a chip U6 and a resistor R307. The model of the chip U6 is OPA228, which can realize the voltage following function. The resistor R307 is a current limiting resistor, which limits the current amplitude of the output signal.

[0077] As an optional implementation, Figure 6As shown, the third acquisition circuit includes: a second effective value conversion unit and a fourth following unit. The second effective value conversion unit is respectively connected to the secondary coil and the fourth following unit in the linear variable differential transformer sensor; the fourth following unit is connected to the data processing circuit. The second effective value conversion unit is used to reduce the ratio of the induced voltage signal generated by the secondary coil, and convert the reduced-ratio induced voltage signal into an effective value signal in the form of a DC voltage signal, and then output it to the fourth following unit. The fourth following unit is used to perform voltage following on the effective value signal of the induced voltage signal, while adjusting the line impedance characteristics, and output the effective value signal of the induced voltage signal to the data processing circuit.

[0078] Figure 6 The third acquisition circuit shown is composed of a second effective value conversion unit and a fourth follower unit. The second effective value conversion unit is composed of an effective value conversion chip and related adjustment elements such as resistors and capacitors. It reduces the ratio of the induced voltage signal of the secondary coil, converts it into an effective value signal in the form of a DC voltage signal, and outputs it to the fourth follower unit. The fourth follower unit is a voltage follower circuit composed of an operational amplifier and a current limiting resistor, which adjusts the line impedance characteristics and outputs the effective value signal of the induced voltage signal to the data processing circuit.

[0079] Reference Fig.11 , the working principle of the third acquisition circuit is explained with an actual circuit. The second effective value conversion unit is composed of chip U7, resistor R401, resistor R402, capacitor C401 and capacitor C402. Chip U7 is an effective value converter, model LTC1968, which can obtain the effective value of the input signal and output it in the form of a DC voltage signal. Resistors R401 and R402 are used to adjust the input signal amplitude of chip U3. Capacitor C401 is used to couple the input signal to prevent DC or low-frequency signal input. Capacitor C402 is used to output the signal smoothly. The fourth follower unit is composed of chip U8 and resistor R403. Chip U8 is an operational amplifier, model OPA228, which can realize the voltage following function. Resistor R403 is a current limiting resistor that limits the output signal current amplitude.

[0080] As an optional implementation, Figure 7As shown, the data processing circuit includes: an analog-to-digital conversion unit and a controller unit. The analog-to-digital conversion unit is connected to the first acquisition circuit, the second acquisition circuit, the third acquisition circuit and the controller unit respectively. The analog-to-digital conversion unit is used to convert the effective value signal of the excitation voltage signal, the phase difference signal and the effective value signal of the induced voltage signal from analog quantity to digital quantity, obtain the effective value signal value of the excitation voltage signal, the phase difference signal value and the effective value signal value of the induced voltage signal, and output them to the controller unit. The controller unit is used to perform temperature drift compensation according to the effective value signal value of the excitation voltage signal, the phase difference signal value and the effective value signal value of the induced voltage signal, and obtain the corrected displacement measurement value.

[0081] Figure 7 The data processing circuit shown is composed of an analog-to-digital conversion unit and a controller unit. The analog-to-digital conversion unit is composed of an analog-to-digital conversion chip and auxiliary components such as capacitors and crystal oscillators. It converts the effective value signal of the input excitation voltage signal, the phase difference signal, and the effective value signal of the induced voltage signal from analog to digital, and outputs it to the controller unit through a digital communication interface. The controller unit is composed of auxiliary components such as a microcontroller chip capacitor and a crystal oscillator, obtains the digital signal of the analog-to-digital conversion unit, integrates the pre-set program and data, calculates and corrects the displacement measurement result, and outputs the displacement measurement result through a digital communication interface or a digital-to-analog conversion module.

[0082] Reference Fig.12 , using actual circuits to illustrate the working principle of the data processing circuit. The analog-to-digital conversion unit consists of chip U9, capacitor C501, capacitor C502 and crystal oscillator CY501. Chip U9 is an analog-to-digital converter, model ADS1243, which can convert the input analog signal into a digital signal and send data through the SPI interface. Capacitor C501, capacitor C502 and crystal oscillator CY501 provide a stable clock signal for the analog-to-digital converter. The controller unit consists of chip U10, capacitor C503, capacitor C504 and crystal oscillator CY502. Chip U10 is a microcontroller, model PY32F030F18P7, which can perform calculations, interface control and other tasks according to the internally solidified programs and data, receive and process the output data of the analog-to-digital converter. Capacitor C503, capacitor C504 and crystal oscillator CY502 provide a stable clock signal for the microcontroller.

[0083] The compensation fitting coefficients H1, H2, H3, and H4 of step 1.6 mentioned above are stored in the microcontroller. Step 2.1 reads the compensation fitting coefficients H1, H2, H3, and H4 stored in the microcontroller. Step 2.2: obtain the measured values ​​of signal V3, signal V4, and signal V6 through the analog-to-digital conversion unit, which are recorded as At, Bt, and Ct. After obtaining the corrected displacement measurement value St in step 2.4, the corrected displacement measurement value St is output to an external device through the digital communication interface (SPI, IIC, or UART, etc.) or the digital-to-analog conversion interface of the microcontroller.

[0084] This application can realize the signal excitation, data processing and measurement functions of traditional products, and can also realize the temperature drift compensation function. At the same time, it avoids adding hardware settings to the sensing part, thereby maintaining the original size of the sensing part.

[0085] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A linear variable differential transformer sensor measurement and correction method, characterized in that: include: Get compensation fitting coefficients; Obtaining an effective value signal of an excitation voltage signal, a phase difference signal, and an effective value signal of an induced voltage signal when the displacement of an object to be measured is measured using a linear variable differential transformer sensor; the phase difference signal is a phase difference signal between an excitation voltage signal and an excitation source signal generated by a linear variable differential transformer sensor signal conditioning device when the primary coil in the linear variable differential transformer sensor is excited; According to the effective value signal value of the excitation voltage signal of the object to be measured, the phase difference signal value and the effective value signal value of the induced voltage signal, the compensation fitting coefficient is used to perform temperature drift compensation to obtain a corrected displacement measurement value; Get the compensation fitting coefficients, including: Acquiring effective value signals of an excitation voltage signal, a phase difference signal, and an effective value signal of an induced voltage signal when a linear variable differential transformer sensor is used to measure displacements of gauge blocks of different lengths at a preset ambient temperature; the length of the gauge block is equal to the actual displacement; Calculate the average value of the phase difference signal values ​​of all gauge blocks at a preset ambient temperature; Fitting the corresponding relationship between the ratio at a preset ambient temperature and the length of the gauge block to obtain a first calibration fitting relationship and a first calibration fitting coefficient and a second calibration fitting coefficient in the first calibration fitting relationship; the ratio is a ratio of the effective value signal value of the induced voltage signal to the effective value signal value of the excitation voltage signal; The preset ambient temperature is changed multiple times, and after each change of the preset ambient temperature, the step of "obtaining the effective value signal of the excitation voltage signal, the phase difference signal, and the effective value signal of the induced voltage signal when the displacement of the gauge blocks of different lengths is measured using the linear variable differential transformer sensor at the preset ambient temperature" is returned to obtain the average value of the phase difference signal value under multiple different preset ambient temperatures, the first calibration fitting coefficient, and the second calibration fitting coefficient; Fitting the correspondence between the average value of the phase difference signal values ​​at multiple different preset ambient temperatures and the first calibration fitting coefficient to obtain a second calibration fitting relationship and a third calibration fitting coefficient and a fourth calibration fitting coefficient in the second calibration fitting relationship, and fitting the correspondence between the average value of the phase difference signal values ​​at multiple different preset ambient temperatures and the second calibration fitting coefficient to obtain a third calibration fitting relationship and a fifth calibration fitting coefficient and a sixth calibration fitting coefficient in the third calibration fitting relationship; The third calibration fitting coefficient, the fourth calibration fitting coefficient, the fifth calibration fitting coefficient and the sixth calibration fitting coefficient are determined as compensation fitting coefficients.

2. The linear variable differential transformer sensor measurement and correction method according to claim 1, characterized in that: According to the effective value signal value of the excitation voltage signal of the object to be measured, the phase difference signal value and the effective value signal value of the induced voltage signal, the compensation fitting coefficient is used to perform temperature drift compensation to obtain the corrected displacement measurement value, specifically including: According to the phase difference signal value of the object to be measured, the third calibration fitting coefficient and the fourth calibration fitting coefficient, the value of the first calibration fitting coefficient of the object to be measured is obtained by using the second calibration fitting relationship; According to the phase difference signal value of the object to be measured, the fifth calibration fitting coefficient and the sixth calibration fitting coefficient, using the third calibration fitting relationship, a second calibration fitting coefficient value of the object to be measured is obtained; According to the phase difference signal value, the effective value signal value of the induced voltage signal, the first calibration fitting coefficient value of the object to be measured and the second calibration fitting coefficient value of the object to be measured, the corrected displacement measurement value is obtained using the first calibration fitting relationship.

3. The linear variable differential transformer sensor measurement and correction method according to claim 1, characterized in that: The first calibration fitting relationship is: Si=E1×(C1i / A1i)+F1; Wherein, Si is the measuring length of the gauge block at the i-th measurement under the preset ambient temperature, E1 is the first calibration fitting coefficient, C1i is the effective value signal value of the induced voltage signal at the i-th measurement under the preset ambient temperature, A1i is the effective value signal value of the excitation voltage signal at the i-th measurement under the preset ambient temperature, and F1 is the second calibration fitting coefficient; The second calibration fitting relationship is: Ej=H1×Dj+H2; Wherein, Ej is the first calibration fitting coefficient at the j-th preset ambient temperature, Dj is the average value of the phase difference signal value at the j-th preset ambient temperature, H1 is the third calibration fitting coefficient, and H2 is the fourth calibration fitting coefficient; The third calibration fitting relationship is: Fj=H3×Dj+H4; Wherein, Fj is the second calibration fitting coefficient at the j-th preset ambient temperature, Dj is the average value of the phase difference signal value at the j-th preset ambient temperature, H3 is the fifth calibration fitting coefficient, and H4 is the sixth calibration fitting coefficient.

4. A linear variable differential transformer sensor signal conditioning device, characterized in that: include: A coil excitation circuit, a first acquisition circuit, a second acquisition circuit, a third acquisition circuit and a data processing circuit; The coil excitation circuit is connected to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor respectively; the coil excitation circuit is used to generate an excitation source signal and an excitation voltage signal, and output the excitation voltage signal to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor respectively, and output the excitation source signal to the second acquisition circuit at the same time; The first acquisition circuit is connected to the data processing circuit; the first acquisition circuit is used to obtain the effective value signal of the excitation voltage signal and output it to the data processing circuit; The second acquisition circuit is connected to the data processing circuit; the second acquisition circuit is used to obtain a phase difference signal between the excitation voltage signal and the excitation source signal, and output it to the data processing circuit; The third acquisition circuit is connected to the secondary coil and the data processing circuit in the linear variable differential transformer sensor respectively; the third acquisition circuit is used to collect the induced voltage signal generated by the secondary coil when the linear variable differential transformer sensor measures the displacement of the object to be measured, and output the effective value signal of the induced voltage signal to the data processing circuit; The data processing circuit is used to perform temperature drift compensation according to the effective value signal of the excitation voltage signal, the phase difference signal and the effective value signal of the induced voltage signal, using the linear variable differential transformer sensor measurement correction method described in any one of claims 1 to 3 to obtain a corrected displacement measurement value.

5. The linear variable differential transformer sensor signal conditioning device according to claim 4, characterized in that: The coil excitation circuit comprises: a waveform generating unit and a first following unit; The first follower unit includes an operational amplifier and a current limiting resistor; The waveform generating unit is connected to the operational amplifier; the waveform generating unit is used to generate a sine wave signal and output it to the operational amplifier; The operational amplifier is connected to the current limiting resistor and the second acquisition circuit respectively, and the current limiting resistor is also connected to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor; the operational amplifier is used to perform voltage following on the sinusoidal wave signal, obtain the excitation source signal, and output the excitation source signal to the current limiting resistor and the second acquisition circuit respectively; the current limiting resistor is used to limit the primary coil current, adjust the signal phase, obtain the excitation voltage signal, and output the excitation voltage signal to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor respectively.

6. The linear variable differential transformer sensor signal conditioning device according to claim 4, characterized in that: The first acquisition circuit includes: a first effective value conversion unit and a second following unit; The first effective value conversion unit is connected to the coil excitation circuit and the second follower unit respectively; the first effective value conversion unit is used to reduce the ratio of the excitation voltage signal generated by the coil excitation circuit, and convert the reduced-ratio excitation voltage signal into an effective value signal in the form of a DC voltage signal, and then output it to the second follower unit; The second follower unit is connected to the data processing circuit; the second follower unit is used to perform voltage following on the effective value signal of the excitation voltage signal, adjust the line impedance characteristics, and output the effective value signal of the excitation voltage signal to the data processing circuit.

7. The linear variable differential transformer sensor signal conditioning device according to claim 4, characterized in that: The second acquisition circuit includes: a phase difference measurement unit and a third following unit; The phase difference measuring unit is connected to the coil excitation circuit and the third follower unit respectively; the phase difference measuring unit is used to obtain a phase difference signal between the excitation voltage signal and the excitation source signal, and output the phase difference signal to the third follower unit in the form of a DC voltage signal; The third follower unit is connected to the data processing circuit; the third follower unit is used to perform voltage following on the phase difference signal in the form of a DC voltage signal, adjust the line impedance characteristics, and output the phase difference signal in the form of a DC voltage signal to the data processing circuit.

8. The linear variable differential transformer sensor signal conditioning device according to claim 4, characterized in that: The third acquisition circuit comprises: a second effective value conversion unit and a fourth following unit; The second effective value conversion unit is connected to the secondary coil and the fourth follower unit in the linear variable differential transformer sensor respectively; the second effective value conversion unit is used to reduce the ratio of the induced voltage signal generated by the secondary coil, and convert the reduced-ratio induced voltage signal into an effective value signal in the form of a DC voltage signal, and then output it to the fourth follower unit; The fourth follower unit is connected to the data processing circuit; the fourth follower unit is used to perform voltage following on the effective value signal of the induced voltage signal, adjust the line impedance characteristics, and output the effective value signal of the induced voltage signal to the data processing circuit.

9. The linear variable differential transformer sensor signal conditioning device according to claim 4, characterized in that: The data processing circuit comprises: an analog-to-digital conversion unit and a controller unit; The analog-to-digital conversion unit is connected to the first acquisition circuit, the second acquisition circuit, the third acquisition circuit and the controller unit respectively; the analog-to-digital conversion unit is used to convert the effective value signal of the excitation voltage signal, the phase difference signal and the effective value signal of the induced voltage signal from analog quantity to digital quantity, obtain the effective value signal value of the excitation voltage signal, the phase difference signal value and the effective value signal value of the induced voltage signal, and output them to the controller unit; The controller unit is used to perform temperature drift compensation according to the effective value signal value of the excitation voltage signal, the phase difference signal value and the effective value signal value of the induced voltage signal to obtain a corrected displacement measurement value.

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