Measurement correction method and signal conditioning apparatus for linear variable differential transformer sensor

Abstract

A measurement correction method and signal conditioning apparatus for a linear variable differential transformer sensor. The correction method comprises the following steps: acquiring a compensation fitting coefficient (101); obtaining a root mean square value signal of an excitation voltage signal, a phase difference signal and a root mean square value signal of an induced voltage signal of when a linear variable differential transformer sensor is used to measure the displacement of an object to be measured (102); and on the basis of the numerical value of the root mean square value signal of the excitation voltage signal, the numerical value of the phase difference signal and the numerical value of the root mean square value signal of the induced voltage signal of said object and in view of the compensation fitting coefficient, performing temperature drift compensation, so as to obtain a corrected displacement measurement value (103). The above solution can compensate for the displacement data drift caused by the impact of temperature on a linear variable differential transformer sensor, thereby reducing the impact of temperature drift on the output of the linear variable differential transformer sensor.

Description

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

[0001] The present application claims priority to the Chinese patent application No. 202411266024.1, filed on September 11, 2024, and entitled "Linear variable differential transformer sensor measurement correction method and signal conditioning device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of linear variable differential transformer sensors, in particular to a linear variable differential transformer sensor measurement correction method and signal conditioning device. BACKGROUND

[0003] The LVDT (Linear Variable Differential Transformer) sensor is a commonly used displacement measurement sensor, which can output the linear displacement measurement results through a direct current analog quantity or a digital communication interface, and has the advantages of high sensitivity, simple structure, long service life, etc. The LVDT sensor is widely used in various industrial control, scientific research and measurement fields.

[0004] The sensing part of the LVDT sensor mainly consists of a primary coil, a secondary coil and a core. The common LVDT sensor contains two secondary coils connected in reverse series. When the primary coil is connected with an alternating voltage, the secondary coil will generate an induced voltage. When the core in the sensing part moves with the measured object, the induced voltages of the two secondary coils will change differently. By analyzing and processing the values of the induced voltages, the displacement of the core can be inferred.

[0005] However, in the development of actual products, the LVDT sensor is often affected by environmental temperature or its own temperature rise, resulting in a result deviation. Therefore, it is necessary to correct the obtained displacement measurement results. SUMMARY

[0006] The purpose of the present application is to provide a linear variable differential transformer sensor measurement correction method and signal conditioning device, which can compensate for the displacement data drift of the linear variable differential transformer sensor caused by temperature influence and reduce the temperature drift influence of the linear variable differential transformer sensor output.

[0007] To achieve the above purpose, the present application provides the following solutions.

[0008] In a first aspect, the application provides a linear variable differential transformer sensor measurement correction method, comprising: obtaining 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 a linear variable differential transformer sensor is used to measure displacement of an object; the phase difference signal is a phase difference signal between the excitation voltage signal generated by a linear variable differential transformer sensor signal conditioning device when exciting a primary coil in the linear variable differential transformer sensor and an excitation source signal; 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, temperature drift compensation is performed by using the compensation fitting coefficients to obtain a corrected displacement measurement value.

[0009] In a second aspect, the 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 connected to the first acquisition circuit, the second acquisition circuit and a 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. 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 connected to a secondary coil in the linear variable differential transformer sensor and the data processing circuit respectively; the third acquisition circuit is used to acquire an induced voltage signal generated by the secondary coil when the linear variable differential transformer sensor measures displacement of an object, and output an effective value signal of the induced voltage signal to the data processing circuit. The data processing circuit is used to perform temperature drift compensation by using the linear variable differential transformer sensor measurement correction method 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, to obtain a corrected displacement measurement value.

[0010] According to the specific embodiments provided by the application, the following technical effects are disclosed.

[0011] The application provides a linear variable differential transformer sensor measurement correction method and a signal conditioning device. The phase difference signal between the excitation voltage signal generated by the linear variable differential transformer sensor signal conditioning device when exciting the primary coil in the linear variable differential transformer sensor and the excitation source signal is measured, and the displacement measured by the linear variable differential transformer sensor is temperature drift compensated by combining the compensation fitting coefficient. The displacement data drift of the linear variable differential transformer sensor caused by temperature is compensated, and the temperature drift influence of the linear variable differential transformer sensor output is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0013] Fig. 1 is a flowchart of a linear variable differential transformer sensor measurement correction method provided by an embodiment of the present application.

[0014] Fig. 2 is a schematic diagram of the circuit composition of a linear variable differential transformer sensor signal conditioning device provided by an embodiment of the present application.

[0015] Fig. 3 is a schematic diagram of a coil excitation circuit provided by an embodiment of the present application.

[0016] Fig. 4 is a schematic diagram of a first acquisition circuit provided by an embodiment of the present application.

[0017] Fig. 5 is a schematic diagram of a second acquisition circuit provided by an embodiment of the present application.

[0018] Fig. 6 is a schematic diagram of a third acquisition circuit provided by an embodiment of the present application.

[0019] Fig. 7 is a schematic diagram of a data processing circuit provided by an embodiment of the present application.

[0020] Fig. 8 is a schematic diagram of a coil excitation circuit design provided by an embodiment of the present application.

[0021] Fig. 9 is a schematic diagram of a first acquisition circuit design provided by an embodiment of the present application.

[0022] Fig. 10 is a schematic diagram of a second acquisition circuit design provided by an embodiment of the present application.

[0023] Fig. 11 is a schematic diagram of a third acquisition circuit design provided by an embodiment of the present application.

[0024] Fig. 12 is a schematic diagram of a data processing circuit design provided by an embodiment of the present application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0026] The above purposes, features and advantages of the present application will be more apparent and understandable. The present application will be further described in detail below with reference to the drawings and specific embodiments.

[0027] In one exemplary embodiment, as shown in FIG. 1, a linear variable differential transformer sensor measurement correction method is provided, comprising the following steps 101 to 103.

[0028] Step 101: Obtain compensation fitting coefficients.

[0029] Step 102: Obtain 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 the object to be measured using the linear variable differential transformer sensor. The phase difference signal is the phase difference signal between the excitation voltage signal generated by the linear variable differential transformer sensor signal conditioning device when exciting the primary coil of the linear variable differential transformer sensor and the excitation source signal.

[0030] 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 temperature drift compensation is performed by using the compensation fitting coefficients to obtain the corrected displacement measurement value.

[0031] By implementing the above steps 101 to 103, the phase difference signal between the excitation voltage signal generated by the linear variable differential transformer sensor signal conditioning device when exciting the primary coil of the linear variable differential transformer sensor and the excitation source signal is measured, and the displacement measured by the linear variable differential transformer sensor is compensated for temperature drift by combining the compensation fitting coefficients. The displacement data drift caused by the linear variable differential transformer sensor affected by temperature is compensated, and the temperature drift influence of the linear variable differential transformer sensor output is reduced.

[0032] In another exemplary embodiment of the present application, in order to determine the compensation fitting coefficients, the above step 101 is replaced by the following steps 201 to 206.

[0033] Step 201: Obtain the RMS value signal of the excitation voltage signal, the phase difference signal and the RMS value signal of the induced voltage signal when measuring displacement of different lengths of the gauge block using the linear variable differential transformer sensor at a preset ambient temperature; the length of the gauge block is equal to the actual displacement amount.

[0034] Step 202: Calculate the average value of the phase difference signal values of all the gauge blocks at the preset ambient temperature.

[0035] Step 203: Fit the corresponding relationship between the ratio and the length of the gauge block at the preset ambient temperature to obtain a first calibration fitting relationship and first and second calibration fitting coefficients in the first calibration fitting relationship. The ratio is the ratio of the RMS value signal of the induced voltage signal to the RMS value signal of the excitation voltage signal.

[0036] Step 204: Change the preset ambient temperature multiple times, and after changing the preset ambient temperature each time, return to the step of "obtaining the RMS value signal of the excitation voltage signal, the phase difference signal and the RMS value signal of the induced voltage signal when measuring displacement of different lengths of the gauge block using the linear variable differential transformer sensor at a preset ambient temperature" to obtain the average value of the phase difference signal values, the first calibration fitting coefficient and the second calibration fitting coefficient at multiple different preset ambient temperatures.

[0037] Step 205: Fit the corresponding relationship between the average value of the phase difference signal values and the first calibration fitting coefficient at multiple different preset ambient temperatures to obtain a second calibration fitting relationship and third and fourth calibration fitting coefficients in the second calibration fitting relationship, and fit the corresponding relationship between the average value of the phase difference signal values and the second calibration fitting coefficient at multiple different preset ambient temperatures to obtain a third calibration fitting relationship and fifth and sixth calibration fitting coefficients in the third calibration fitting relationship.

[0038] Step 206: Determine the third, fourth, fifth and sixth calibration fitting coefficients as compensation fitting coefficients.

[0039] In another exemplary embodiment of the present application, on the basis of steps 201-206, the detailed implementation process of the above step 103 is as follows: steps 301-303.

[0040] 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 first calibration fitting coefficient value of the object to be measured is obtained by using the second calibration fitting relationship.

[0041] Step 302: obtaining the second calibration fitting coefficient value of the object to be measured according to the phase difference signal value, the fifth calibration fitting coefficient and the sixth calibration fitting coefficient of the object to be measured, and using the third calibration fitting relationship.

[0042] Step 303: obtaining the corrected displacement measurement value 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, and using the first calibration fitting relationship.

[0043] In another exemplary embodiment of the present application, a specific form of the first calibration fitting relationship obtained in step 203 is as follows. Si=E1×(C1i / A1i)+F1.

[0044] In the formula, Si is the 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.

[0045] A specific form of the second calibration fitting relationship obtained in step 205 is as follows. Ej=H1×Dj+H2.

[0046] In the formula, Ej is the first calibration fitting coefficient under the j-th preset ambient temperature, Dj is the average value of the phase difference signal value under the j-th preset ambient temperature, H1 is the third calibration fitting coefficient, and H2 is the fourth calibration fitting coefficient.

[0047] A specific form of the third calibration fitting relationship obtained in step 205 is as follows. Fj=H3×Dj+H4.

[0048] In the formula, Fj is the second calibration fitting coefficient under the j-th preset ambient temperature, Dj is the average value of the phase difference signal value under the j-th preset ambient temperature, H3 is the fifth calibration fitting coefficient, and H4 is the sixth calibration fitting coefficient.

[0049] The effective value signal of the excitation voltage signal is represented by signal V3, the phase difference signal is represented by signal V4, and the effective value signal of the induced voltage signal is represented by signal V6. Based on this, the determination method of the compensation fitting coefficient and the displacement correction method are described in a more specific implementation process as follows.

[0050] Taking a gauge block as an example, the determination method of the compensation fitting coefficient is as follows. Steps 1.1-1.6. The standard gauge block is a standard end face gauge without scale.

[0051] Step 1.1: Measure the standard gauge block with LVDT sensor at ambient temperature t1, the length of the gauge block is S1, obtain the value of signal V3, signal V4 and signal V6 at ambient temperature t1, respectively recorded as A11, B11 and C11.

[0052] Step 1.2: Keep the ambient temperature unchanged, replace the standard gauge block, repeat the measurement, the length of the standard gauge block is S2, S3, …, Sm respectively, obtain the value of signal V3, signal V4 and signal V6, recorded as A12, B12, C12, A13, B13, C13, …, A1m, B1m, C1m.

[0053] Step 1.3: Calculate the average value of signal V4, recorded as D1, that is i is in the range of 1 to m, m represents the number of measurements, and B1i is the value of the phase difference signal at the i-th measurement at the preset ambient temperature.

[0054] Step 1.4: Use least squares method or other linear fitting algorithm to fit the corresponding relationship between the ratio of signal V6 value and signal V3 value and the length of the gauge block, obtain the first calibration fitting coefficient and the second calibration fitting coefficient, recorded as E1 and F1, that is Si = E1 × (C1i / A1i) + F1, i is in the range of 1 to m.

[0055] Step 1.5: Change the ambient temperature to t2, t3, …, tn, after changing the ambient temperature each time, repeat steps 1.1, 1.2, 1.3 and 1.4, obtain the average value of signal V4, the first calibration fitting coefficient and the second calibration fitting coefficient, respectively D2, E2, F2, D3, E3, F3, …, Dn, En, Fn. Wherein, n represents the number of ambient temperature.

[0056] Step 1.6: Use least squares method or other linear fitting algorithm to fit the average value of signal V4 and the first calibration fitting coefficient and the second calibration fitting coefficient, obtain the compensation fitting coefficient, recorded as H1, H2, H3, H4, that is Ej = H1 × Dj + H2, Fj = H3 × Dj + H4, j is in the range of 1 to n.

[0057] The displacement correction method is shown in steps 2.1-2.4 below.

[0058] Step 2.1: Read the compensation fitting coefficients H1, H2, H3, H4.

[0059] Step 2.2: Obtain the measured values of signal V3, signal V4 and signal V6, recorded as At, Bt, Ct.

[0060] Step 2.3: Calculate the calibration fitting coefficients Et and Ft using the signal measurement value and compensation fitting coefficients, i.e. Et = H1 x Bt + H2, Ft = H3 x Bt + H4.

[0061] Step 2.4: Calculate the corrected displacement measurement value St using the calibration fitting coefficients, i.e. St = Et x (Ct / At) + Ft.

[0062] The coil part of the LVDT sensor will heat up due to the influence of environmental temperature and self-current heat effect. The inductance in the primary coil of the LVDT sensor includes self-inductance and mutual inductance, wherein the mutual inductance received by the primary coil is less affected by the position of the magnetic core in the sensor measurement, i.e. under the condition that the environmental conditions remain unchanged, the change of the measured object will not basically 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 variation curves, the phase angle of the overall impedance will change with the temperature change. In turn, the size of the sensor temperature drift can be evaluated through 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 of the LVDT sensor caused by temperature influence 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 of the excitation source signal and the excitation voltage signal, so as to obtain the LVDT sensor displacement measurement result with compensation characteristics, and reduce the temperature drift influence of the LVDT sensor output. Currently, the LVDT sensor on the market does not have or does not express the temperature drift compensation function.

[0063] Based on the same inventive concept, the present application also provides a linear variable differential transformer sensor signal conditioning device, as shown in FIG. 2, 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 connected with the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor respectively; the first acquisition circuit is connected with the data processing circuit; the second acquisition circuit is connected with the data processing circuit; the third acquisition circuit is connected with the secondary coil in the linear variable differential transformer sensor and the data processing circuit respectively.

[0064] The coil excitation circuit is used for generating an excitation source signal and an excitation voltage signal, and outputting 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 outputting the excitation source signal to the second acquisition circuit. The first acquisition circuit is used for obtaining a root mean square signal of the excitation voltage signal and outputting the root mean square signal to the data processing circuit. The second acquisition circuit is used for obtaining a phase difference signal of the excitation voltage signal and the excitation source signal and outputting the phase difference signal to the data processing circuit. The third acquisition circuit is used for collecting an 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 outputting a root mean square signal of the induced voltage signal to the data processing circuit. The data processing circuit is used for performing temperature drift compensation by using the above-mentioned linear variable differential transformer sensor measurement correction method according to the root mean square signal of the excitation voltage signal, the phase difference signal and the root mean square signal of the induced voltage signal, and obtaining a corrected displacement measurement value.

[0065] The existing method needs to measure the temperature value to compensate for the temperature drift. Therefore, in the hardware design, a temperature measuring device needs to be installed on the LVDT sensor coil, and a wire circuit needs to be added between the coil and the signal conditioning circuit to transmit the temperature signal. This increases the size of the LVDT sensor sensing part, which is not convenient for product miniaturization design. The device of the present application does not need to increase the hardware settings of the LVDT sensor sensing part, but measures the signal on the original transmission line. While increasing the function, the original size of the LVDT sensor sensing part is maintained.

[0066] As an optional implementation, the coil excitation circuit is responsible for exciting the primary coil. As shown in FIG. 3, 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 with the operational amplifier; the operational amplifier is connected with the current limiting resistor and the second acquisition circuit respectively, and the current limiting resistor is also connected with 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 for generating a sine wave signal and outputting the sine wave signal to the operational amplifier; the operational amplifier is used for voltage following the sine wave signal, obtaining an excitation source signal and outputting the excitation source signal to the current limiting resistor and the second acquisition circuit respectively; and the current limiting resistor is used for limiting the primary coil current, adjusting the signal phase, obtaining an excitation voltage signal and outputting the excitation voltage signal to the first acquisition circuit, the second acquisition circuit and the primary coil in the linear variable differential transformer sensor.

[0067] Referring to Fig. 3, the coil excitation circuit mainly consists of a waveform generating unit and a first following unit. The waveform generating unit consists of a waveform generating chip and related adjusting elements such as resistors and capacitors, generates a sine wave signal and outputs the signal to the first following unit. The first following unit is a voltage following circuit consisting of an operational amplifier and a current-limiting resistor, adjusts the line impedance characteristic, and outputs the 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.

[0068] Referring to Fig. 8, the working principle of the coil excitation circuit is explained by an actual circuit. The waveform generating unit consists of a chip U1, resistors R102, R103, R104, R105, and a capacitor C101. The chip U1 is a waveform generator, model ICL8038, which can generate a sine wave signal. The resistors R102, R103, and the capacitor C101 are used to adjust the frequency of the output sine wave. The resistors R104 and R105 are used to adjust the waveform distortion rate. The first following unit consists of a chip U2 and a resistor R101. The chip U2 is an operational amplifier, model OPA228, which can realize voltage following function. The resistor R101 is a current-limiting resistor which limits the primary coil current.

[0069] As an optional embodiment, as shown in Fig. 4, the first acquisition circuit includes a first effective value conversion unit and a second following unit. The first effective value conversion unit is connected with the coil excitation circuit and the second following unit respectively; the second following unit is connected with the data processing circuit. The first effective value conversion unit is used to reduce the proportion of the excitation voltage signal generated by the coil excitation circuit, and convert the excitation voltage signal in the form of a direct current voltage signal into an effective value signal after reducing the proportion, and then output the effective value signal to the second following unit. The second following unit is used to voltage follow the effective value signal of the excitation voltage signal, adjust the line impedance characteristic at the same time, and output the effective value signal of the excitation voltage signal to the data processing circuit.

[0070] Referring to Fig. 4, the first acquisition circuit consists of a first effective value conversion unit and a second following unit. The first effective value conversion unit consists of an effective value conversion chip and related adjusting elements such as resistors and capacitors, reduces the proportion of the excitation voltage signal, converts the excitation voltage signal into an effective value signal in the form of a direct current voltage signal, and outputs the effective value signal to the second following unit. The second following unit is a voltage following circuit consisting of an operational amplifier and a current-limiting resistor, adjusts the line impedance characteristic, and outputs the effective value signal of the excitation voltage signal to the data processing circuit.

[0071] Referring to Fig. 9, the working principle of the first acquisition circuit is explained by 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 number LTC1968, which can obtain the effective value of the input signal and output in the form of a direct current voltage signal. Resistor R201 and resistor R202 are used to adjust the input signal amplitude of chip U3. Capacitor C201 is used to couple the input signal to prevent direct current or low frequency signal input. Capacitor C202 is used to smooth the output signal. The second following unit is composed of chip U4 and resistor R203. Chip U4 is an operational amplifier, model number OPA228, which can realize voltage following function. Resistor R203 is a current limiting resistor which limits the output signal current amplitude.

[0072] As an optional embodiment, as shown in Fig. 5, the second acquisition circuit comprises a phase difference measurement unit and a third following unit. The phase difference measurement unit is connected with the coil excitation circuit and the third following unit respectively; the third following unit is connected with the data processing circuit. The phase difference measurement unit is used to obtain the phase difference signal between the excitation voltage signal and the excitation source signal, and output the phase difference signal in the form of a direct current voltage signal to the third following unit. The third following unit is used to perform voltage following on the phase difference signal in the form of a direct current voltage signal, adjust the line impedance characteristics at the same time, and output the phase difference signal in the form of a direct current voltage signal to the data processing circuit.

[0073] The second acquisition circuit shown in Fig. 5 is composed of a phase difference measurement unit and a third following unit. The phase difference measurement unit is composed of a phase detection chip and related adjusting elements such as resistor and capacitor, which converts the phase difference between the excitation voltage signal and the excitation source signal in the form of a direct current voltage signal and outputs to the third following unit. The third 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 the phase difference signal to the data processing circuit.

[0074] Referring to Fig. 10, the working principle of the second acquisition circuit is explained by 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 in the form of direct current voltage signal. Resistor R301, resistor R302, resistor R303, resistor R304, resistor R305 and resistor R306 are used to adjust the input signal amplitude of chip U5. Capacitor C301, capacitor C302, capacitor C303 and capacitor C304 are used to couple input signal to prevent direct current or low frequency signal input. Capacitor C305 and capacitor C306 provide low pass filter for output signal. The third follow-up unit is composed of chip U6 and resistor R307. Chip U6 is model OPA228, which can realize voltage following function. Resistor R307 is a current limiting resistor, which limits the output signal current amplitude.

[0075] As an optional embodiment, as shown in Fig. 6, the third acquisition circuit comprises a second effective value conversion unit and a fourth follow-up unit. The second effective value conversion unit is connected with the secondary coil in the linear variable differential transformer sensor and the fourth follow-up unit respectively; the fourth follow-up unit is connected with the data processing circuit. The second effective value conversion unit is used to reduce the proportion of the induced voltage signal generated by the secondary coil, and convert the reduced proportion of the induced voltage signal into an effective value signal in the form of direct current voltage signal, and then output to the fourth follow-up unit. The fourth follow-up unit is used to voltage follow-up on the effective value signal of the induced voltage signal, adjust the line impedance characteristic at the same time, and output the effective value signal of the induced voltage signal to the data processing circuit.

[0076] The third acquisition circuit shown in Fig. 6 is composed of a second effective value conversion unit and a fourth follow-up unit. The second effective value conversion unit is composed of effective value conversion chip and related adjusting elements such as resistor and capacitor, which reduces the proportion of the induced voltage signal of the secondary coil, converts it into an effective value signal in the form of direct current voltage signal, and outputs to the fourth follow-up unit. The fourth follow-up unit is a voltage follow-up circuit composed of operational amplifier and current limiting resistor, which adjusts the line impedance characteristic, and outputs the effective value signal of the induced voltage signal to the data processing circuit.

[0077] Referring to FIG. 11, the working principle of the third acquisition circuit is explained by using actual circuit. The second effective value conversion unit is composed of a chip U7, a resistor R401, a resistor R402, a capacitor C401 and a capacitor C402. The chip U7 is an effective value converter, model number LTC1968, which can obtain the effective value of the input signal and output in the form of a direct current voltage signal. The resistor R401 and the resistor R402 are used to adjust the input signal amplitude of the chip U3. The capacitor C401 is used to couple the input signal to prevent direct current or low frequency signal input. The capacitor C402 is used to smooth the output signal. The fourth following unit is composed of a chip U8 and a resistor R403. The chip U8 is an operational amplifier, model number OPA228, which can realize the voltage following function. The resistor R403 is a current limiting resistor which limits the output signal current amplitude.

[0078] As an optional embodiment, as shown in FIG. 7, the data processing circuit comprises an analog-digital conversion unit and a controller unit. The analog-digital conversion unit is connected with the first acquisition circuit, the second acquisition circuit, the third acquisition circuit and the controller unit respectively. The analog-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 to the controller unit. The controller unit is used to compensate the temperature drift 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.

[0079] The data processing circuit shown in FIG. 7 is composed of an analog-digital conversion unit and a controller unit. The analog-digital conversion unit is composed of an analog-digital conversion chip and auxiliary elements such as capacitors and crystal oscillators. The input effective value signal of the excitation voltage signal, the phase difference signal and the effective value signal of the induced voltage signal are converted from analog quantity to digital quantity, and output to the controller unit through a digital communication interface. The controller unit is composed of a microcontroller chip and auxiliary elements such as capacitors and crystal oscillators. The digital quantity signal of the analog-digital conversion unit is obtained, the pre-set program and data are integrated, the displacement measurement result is calculated and corrected, and the displacement measurement result is output through a digital communication interface or a digital-analog conversion module.

[0080] Referring to FIG. 12, the working principle of the data processing circuit is explained with actual circuit. The analog-to-digital conversion unit is composed of chip U9, capacitor C501, capacitor C502 and crystal oscillator CY501. Chip U9 is an analog-to-digital converter, model number 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 is composed of chip U10, capacitor C503, capacitor C504 and crystal oscillator CY502. Chip U10 is a microcontroller, model number PY32F030F18P7, which can perform tasks such as calculation and interface control according to the internal fixed program 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.

[0081] 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: obtains the measured values of signal V3, signal V4 and signal V6 through the analog-to-digital conversion unit, denoted 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 the external device through the digital communication interface (SPI, IIC or UART, etc.) or the digital-to-analog conversion interface of the microcontroller.

[0082] The present application can realize the signal excitation, data processing and measurement functions of traditional products, and also realize the temperature drift compensation function. At the same time, it avoids adding hardware settings in the sensing part, thereby maintaining the original size of the sensing part.

[0083] The technical features of the above embodiments can be combined in any way. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0084] The principles and implementation modes of the present application are described by specific examples in this paper, and the above examples are only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In conclusion, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A method of linear variable differential transformer sensor measurement correction, the method comprising: include: Obtain the compensation fitting coefficients; The effective values ​​of the excitation voltage signal, phase difference signal, and induced voltage signal are obtained when measuring the displacement of the object under test using a linear variable differential transformer sensor. The phase difference signal is the phase difference signal between the excitation voltage signal generated by the linear variable differential transformer sensor signal conditioning device and the excitation source signal when the primary coil in the linear variable differential transformer sensor is excited. Based on the effective values ​​of the excitation voltage signal, phase difference signal, and induced voltage signal of the object under test, temperature drift compensation is performed using the compensation fitting coefficient to obtain the corrected displacement measurement value.

2. The LVDT sensor measurement correction method of claim 1, wherein, To obtain the compensation fitting coefficients, including: The effective values ​​of the excitation voltage signal, phase difference signal, and induced voltage signal are obtained when measuring the displacement of gauge blocks of different lengths using a linear variable differential transformer sensor 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 of all gauge blocks at the preset ambient temperature; The correspondence between the ratio and the length of the gauge block under a preset ambient temperature is fitted to obtain the first calibration fitting formula and the first calibration fitting coefficient and the second calibration fitting coefficient in the first calibration fitting formula; the ratio is the ratio of the effective value of the induced voltage signal to the effective value of the excitation voltage signal. The preset ambient temperature is changed multiple times. After each change, the process returns to the step "Obtain the effective value of the excitation voltage signal, phase difference signal, and induced voltage signal when measuring the displacement of gauge blocks of different lengths using a linear variable differential transformer sensor under the preset ambient temperature". The average value of the phase difference signal, the first calibration fitting coefficient, and the second calibration fitting coefficient are obtained under multiple different preset ambient temperatures. The correspondence between the average value of the phase difference signal under multiple different preset ambient temperatures and the first calibration fitting coefficient is fitted to obtain the second calibration fitting formula and the third and fourth calibration fitting coefficients in the second calibration fitting formula. The correspondence between the average value of the phase difference signal under multiple different preset ambient temperatures and the second calibration fitting coefficient is fitted to obtain the third calibration fitting formula and the fifth and sixth calibration fitting coefficients in the third calibration fitting formula. The third, fourth, fifth, and sixth calibration fitting coefficients were determined as compensation fitting coefficients.

3. The LVDT sensor measurement correction method of claim 2, wherein, Based on the effective values ​​of the excitation voltage signal, phase difference signal, and induced voltage signal of the object under test, temperature drift compensation is performed using the compensation fitting coefficients to obtain the corrected displacement measurement value, including: Based on the phase difference signal value of the object under test, the third calibration fitting coefficient, and the fourth calibration fitting coefficient, the first calibration fitting coefficient value of the object under test is obtained using the second calibration fitting formula. 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 third calibration fitting relationship is used to obtain the second calibration fitting coefficient value of the object to be measured; 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 first calibration fitting relationship is used to obtain the corrected displacement measurement value.

4. The LVDT sensor measurement correction method of claim 2, wherein, The first calibration fitting relationship is: Si=E1×(C1i / A1i)+F1; In the formula, Si is the measurement length of the gauge block at the i-th measurement under the preset environmental 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 environmental temperature, A1i is the effective value signal value of the excitation voltage signal at the i-th measurement under the preset environmental temperature, and F1 is the second calibration fitting coefficient; The second calibration fitting relationship is: Ej=H1×Dj+H2; In the formula, Ej is the first calibration fitting coefficient under the j-th preset environmental temperature, Dj is the average value of the phase difference signal value under the j-th preset environmental 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; In the formula, Fj is the second calibration fitting coefficient under the j-th preset environmental temperature, Dj is the average value of the phase difference signal value under the j-th preset environmental temperature, H3 is the fifth calibration fitting coefficient, and H4 is the sixth calibration fitting coefficient.

5. A linear variable differential transformer sensor signal conditioning device, characterized by, It comprises: 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 with 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; The first acquisition circuit is connected with the data processing circuit; the first acquisition circuit is used to obtain the effective value signal of the excitation voltage signal and output to the data processing circuit; The second acquisition circuit is connected with the data processing circuit; the second acquisition circuit is used to obtain the phase difference signal of the excitation voltage signal and the excitation source signal and output to the data processing circuit; The third acquisition circuit is connected with the secondary coil in the linear variable differential transformer sensor and the data processing circuit 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 compensate the temperature drift by using the linear variable differential transformer sensor measurement correction method 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, and obtain the corrected displacement measurement value.

6. The LVDT sensor signal conditioning device of claim 5, wherein, The coil excitation circuit comprises a waveform generating unit and a first following unit; The first following unit comprises an operational amplifier and a current limiting resistor; The waveform generating unit is connected with the operational amplifier, and is configured to generate a sine wave signal and output the sine wave signal to the operational amplifier; The operational amplifier is connected with the current limiting resistor and a second acquisition circuit respectively, and the current limiting resistor is also connected with a first acquisition circuit, the second acquisition circuit and a primary coil in the linear variable differential transformer sensor; the operational amplifier is configured to perform voltage following on the sine wave signal to obtain an excitation source signal, and output the excitation source signal to the current limiting resistor and the second acquisition circuit respectively; and the current limiting resistor is configured to limit a primary coil current, adjust a 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.

7. The LVDT sensor signal conditioning device of claim 5, wherein, The first acquisition circuit comprises a first effective value conversion unit and a second following unit; The first effective value conversion unit is connected with the coil excitation circuit and the second following unit respectively; the first effective value conversion unit is configured to reduce a proportion of the excitation voltage signal generated by the coil excitation circuit, convert the excitation voltage signal with the reduced proportion into an effective value signal in the form of a direct current voltage signal, and output the effective value signal to the second following unit; The second following unit is connected with a data processing circuit; the second following unit is configured to perform voltage following on the effective value signal of the excitation voltage signal, adjust a line impedance characteristic at the same time, and output the effective value signal of the excitation voltage signal to the data processing circuit.

8. The LVDT sensor signal conditioning device of claim 5, wherein, The second acquisition circuit comprises a phase difference measurement unit and a third following unit; The phase difference measurement unit is connected with the coil excitation circuit and the third following unit respectively; the phase difference measurement unit is configured 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 direct current voltage signal; The third following unit is connected with the data processing circuit; the third following unit is configured to perform voltage following on the phase difference signal in the form of a direct current voltage signal, adjust a line impedance characteristic at the same time, and output the phase difference signal in the form of a direct current voltage signal to the data processing circuit.

9. The LVDT sensor signal conditioning device of claim 5, wherein, The third acquisition circuit comprises a second effective value conversion unit and a fourth following unit; The second effective value conversion unit is connected with a secondary coil in the linear variable differential transformer sensor and the fourth following unit respectively; the second effective value conversion unit is configured to reduce a proportion of an induced voltage signal generated by the secondary coil, convert the induced voltage signal with the reduced proportion into an effective value signal in the form of a direct current voltage signal, and output the effective value signal to the fourth following unit; The fourth following unit is connected with the data processing circuit; the fourth following unit is configured to perform voltage following on the effective value signal of the induced voltage signal, adjust a line impedance characteristic at the same time, and output the effective value signal of the induced voltage signal to the data processing circuit.

10. The LVDT sensor signal conditioning device of claim 5, wherein, The data processing circuit comprises an analog-digital conversion unit and a controller unit; Analog-digital conversion units are connected with the first acquisition circuit, the second acquisition circuit, the third acquisition circuit and the controller unit respectively; the analog-digital conversion units are used for converting the effective value signals of the excitation voltage signals, the phase difference signals and the effective value signals of the induced voltage signals from analog quantities into digital quantities, obtaining the effective value signal values of the excitation voltage signals, the phase difference signal values and the effective value signal values of the induced voltage signals, and outputting to the controller unit; The controller unit is used for performing temperature drift compensation according to the effective value signal values of the excitation voltage signals, the phase difference signal values and the effective value signal values of the induced voltage signals, and obtaining corrected displacement measurement values.

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