Eddy current sensor temperature compensation circuit

Abstract

The embodiment of the invention discloses a temperature compensation circuit of an eddy current sensor. The temperature compensation circuit comprises an excitation source, an LC resonance unit, a detection unit, a filtering unit, an amplification unit and a temperature compensation unit, the excitation source is used for inputting an alternating current signal; the LC resonance unit is used for forming resonance according to the alternating current signal; the detection unit is used for modulating the alternating current signal after resonance into a direct current signal; the filtering unit is used for filtering the direct current signal; the amplification unit is used for amplifying the filtered direct current signal and then outputting the amplified direct current signal; and the temperature compensation unit is used for compensating the drift distance of the sensitivity of the signal output by the amplification unit under the temperature change and compensating the drift distance of the bias of the input signal of the amplification unit under the temperature change. By implementing the circuit provided by the embodiment of the invention, the sensitivity temperature drift and the bias temperature drift output by the eddy current sensor can be compensated, and the stability and the accuracy of the output of the eddy current sensor are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of eddy current sensors, and particularly to a temperature compensation circuit for an eddy current sensor. Background Art

[0002] Eddy current sensors utilize the principle of electromagnetic induction and are non-contact sensors with high reliability, strong anti-interference ability, and excellent stability. They are suitable for various working environments and are not affected by media such as oil, steam, or dust. The sensor mainly consists of a coil probe and a processing circuit. However, changes in the ambient temperature can cause temperature drift in the coil and the processing circuit, resulting in low detection accuracy of the eddy current sensor.

[0003] Therefore, it is necessary to design a new circuit to compensate for the sensitivity temperature drift and bias temperature drift of the output of the eddy current sensor, ensuring the stability and accuracy of the output of the eddy current sensor. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a temperature compensation circuit for an eddy current sensor.

[0005] To solve the above technical problem, the object of the present invention is achieved through the following technical solutions: providing a temperature compensation circuit for an eddy current sensor, including: an excitation source, an LC resonance unit, a detection unit, a filtering unit, an amplification unit, and a temperature compensation unit; the excitation source is connected to the LC resonance unit; the LC resonance unit is sequentially connected with a detection unit, a filtering unit, and an amplification unit; the temperature compensation unit is connected to the amplification unit; wherein, the excitation source is used to input an alternating current signal; the LC resonance unit is used to form resonance according to the alternating current signal; the detection unit is used to amplitude-modulate the alternating current signal after resonance into a direct current signal; the filtering unit is used to filter the direct current signal; the amplification unit is used to amplify the filtered direct current signal and then output it; the temperature compensation unit is used to compensate for the drift amount of the sensitivity under temperature change of the signal output by the amplification unit and compensate for the drift amount of the bias under temperature change of the input signal of the amplification unit.

[0006] Its further technical solution is: the temperature compensation unit includes a sensitivity temperature compensation module and a bias temperature compensation module, and the amplification unit includes an amplification circuit with a variable amplification factor; the sensitivity temperature compensation module is connected to the output end of the amplification circuit; the bias temperature compensation module is connected to the input end of the amplification circuit.

[0007] Its further technical solution is as follows: The amplifying circuit includes a first amplifier and a second amplifier. The inverting input terminal of the first amplifier is connected to the filtering unit; a sensitivity temperature compensation module is connected between the output terminal of the first amplifier and the inverting input terminal of the first amplifier. The non-inverting input terminal of the first amplifier is connected to the output terminal of the second amplifier. The inverting input terminal of the second amplifier is connected to the output terminal of the second amplifier; the non-inverting input terminal of the second amplifier is connected to the bias temperature compensation module, and the other end of the bias temperature compensation module is grounded.

[0008] Its further technical solution is as follows: A resistor Rf is also connected between the sensitivity temperature compensation module and the inverting input terminal of the first amplifier.

[0009] Its further technical solution is as follows: A resistor R2 is also connected to the non-inverting input terminal of the second amplifier.

[0010] Its further technical solution is as follows: The sensitivity temperature compensation module includes a thermistor Rt1, and the bias temperature compensation module includes a thermistor Rt2.

[0011] Its further technical solution is as follows: The sensitivity temperature compensation module includes a first digital potentiometer; the bias temperature compensation module includes a second digital potentiometer.

[0012] Its further technical solution is as follows: The first digital potentiometer and the second digital potentiometer are respectively connected to a digital temperature compensation controller.

[0013] Its further technical solution is as follows: The digital temperature compensation controller is connected to a temperature sensor.

[0014] Its further technical solution is as follows: The digital temperature compensation controller is used to divide the temperature change range into several small ranges, set a sensitivity temperature compensation coefficient and a bias voltage compensation coefficient in each different range, obtain the current temperature measured by the temperature sensor in real time, determine the sensitivity temperature compensation coefficient and the bias voltage compensation coefficient according to the current temperature, and correspondingly set the coefficients corresponding to the first digital potentiometer and the second digital potentiometer.

[0015] The beneficial effects of the present invention compared with the prior art are as follows: The present invention generates an AC signal through an excitation source, and after being processed by an LC resonance unit, a detection unit, a filtering unit, and an amplifying unit, the temperature compensation unit is used to perform sensitivity and bias compensation on the output signal to offset the influence of temperature changes on the performance of the sensor, so as to realize the compensation of the sensitivity temperature drift and the bias temperature drift of the output of the eddy current sensor, and ensure the stability and accuracy of the output of the eddy current sensor.

[0016] The following further describes the present invention in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a schematic block diagram of a temperature compensation circuit for an eddy current sensor provided by an embodiment of the present invention;

[0019] Figure 2 It is a schematic connection diagram of an amplification unit and a temperature compensation unit provided by an embodiment of the present invention;

[0020] Figure 3 It is a specific circuit schematic diagram of an amplification unit and a temperature compensation unit provided by an embodiment of the present invention;

[0021] Figure 4 It is a specific circuit schematic diagram of an amplification unit and a temperature compensation unit provided by another embodiment of the present invention;

[0022] Figure 5 It is a schematic diagram of the output curve of an amplification unit without temperature compensation provided by an embodiment of the present invention;

[0023] Figure 6 It is a schematic diagram of the output curve of an amplification unit with temperature compensation provided by an embodiment of the present invention;

[0024] Explanation of the reference numerals in the figures:

[0025] 10. Excitation source; 20. LC resonance unit; 30. Detection unit; 40. Filter unit; 50. Amplification unit; 60. Temperature compensation unit. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0027] It should be understood that when used in this specification and the appended claims, the terms "comprises" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0028] It should also be understood that the terms used in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly dictates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0029] It should be further understood that the term "and / or" used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0030] Please refer to Figure 1 , Figure 1 which is a schematic block diagram of a temperature compensation circuit for an eddy current sensor provided by an embodiment of the present invention, and can be applied to scenarios where an eddy current sensor is used to compensate for the sensitivity temperature drift and bias temperature drift of the output of the eddy current sensor, ensuring the stability and accuracy of the output of the eddy current sensor.

[0031] Please refer to Figure 1 The above-mentioned temperature compensation circuit for an eddy current sensor includes: an excitation source 10, an LC resonance unit 20, a detection unit 30, a filtering unit 40, an amplification unit 50, and a temperature compensation unit 60; the excitation source 10 is connected to the LC resonance unit 20; the LC resonance unit 20 is sequentially connected to the detection unit 30, the filtering unit 40, and the amplification unit 50; the temperature compensation unit 60 is connected to the amplification unit 50; wherein, the excitation source 10 is used to input an AC signal; the LC resonance unit 20 is used to form resonance according to the AC signal; the detection unit 30 is used to amplitude-modulate the AC signal after resonance into a DC signal; the filtering unit 40 is used to filter the DC signal; the amplification unit 50 is used to amplify the filtered DC signal and output it; the temperature compensation unit 60 is used to compensate for the drift amount of the sensitivity of the signal output by the amplification unit 50 under temperature change and compensate for the drift amount of the bias of the input signal of the amplification unit 50 under temperature change.

[0032] The temperature compensation unit 60 can effectively offset the influence of temperature changes on the signal, including the sensitivity and the offset drift of the input signal. This can maintain the stability and accuracy of the sensor output, without being affected by environmental temperature changes; Through the orderly connection of the LC resonance unit 20, the detection unit 30, the filtering unit 40, and the amplification unit 50, the original AC input signal can be effectively processed and converted into a stable DC output that is filtered and amplified. Such a signal processing link can improve the response ability and anti-interference ability of the sensor system to the input signal; The temperature compensation mechanism can not only maintain the accuracy of the output in the short term, but also maintain stable performance during long-term use. This is very important for applications that require long-term operation and high reliability, such as industrial automation, aerospace, and scientific instruments, etc.; The temperature compensation ability enables the sensor to work reliably within a wide range of operating temperatures without being affected by temperature changes. This increases the applicability of the sensor and the flexibility of the application scenarios.

[0033] In one embodiment, please refer to Figure 2 , the above-mentioned temperature compensation unit 60 includes a sensitivity temperature compensation module and a bias temperature compensation module, and the amplification unit 50 includes an amplifier circuit with a variable amplification factor; The sensitivity temperature compensation module is connected to the output end of the amplifier circuit; The bias temperature compensation module is connected to the input end of the amplifier circuit.

[0034] In this embodiment, due to the change of the ambient temperature, the output function of the eddy current sensor will produce a certain offset. Assume that the output function after fitting when the eddy current sensor works at room temperature is: y(x) = ax + b; where x represents the input displacement, with the unit of mm; y represents the output voltage of the eddy current sensor, with the unit of V; a represents the sensitivity of the eddy current sensor, with the unit of V / mm, and b represents the offset voltage of the output, with the unit of V.

[0035] Due to the influence of temperature drift, therefore, the output function of the eddy current sensor will change, and its drift change is mainly reflected in the output sensitivity and offset voltage. After the temperature drift occurs, the output function can be expressed as: y(x) = (a + Δ ta )x + (b + Δ tb ); where, Δ ta is the sensitivity temperature drift change; Δ tb is the offset voltage temperature drift change.

[0036] Therefore, for the output temperature drift of the eddy current sensor, it can be compensated by applying sensitivity and bias temperature compensation modules at the output node respectively. The temperature compensation block diagram is as shown in Figure 2 , and mainly includes a sensitivity temperature compensation module and a bias temperature compensation module.

[0037] Sensitivity temperature compensation module: This part can offset the influence of temperature change on the sensor sensitivity by introducing a module with adjustable amplification factor in the amplification unit 50. This means that at different operating temperatures, the system can adjust the amplification factor to maintain the stability and accuracy of the output signal.

[0038] Bias temperature compensation module: This part offsets the influence of temperature change on the output bias by introducing a compensation voltage with characteristics opposite to the temperature drift at the output voltage node. In this way, even when the ambient temperature changes, the reference point of the output signal can be maintained at the desired position, ensuring the reliability and stability of the system under various operating conditions.

[0039] These temperature compensation measures effectively solve the problems of sensitivity and bias drift caused by temperature change during the operation of the eddy current sensor, improve the performance and reliability of the sensor, and enable it to perform stable and accurate measurement functions in a wide range of application scenarios.

[0040] In one embodiment, please refer to Figure 3 and Figure 4 , the amplification circuit includes a first amplifier and a second amplifier. The inverting input terminal of the first amplifier is connected to the filtering unit 40; a sensitivity temperature compensation module is connected between the output terminal of the first amplifier and the inverting input terminal of the first amplifier. The non-inverting input terminal of the first amplifier is connected to the output terminal of the second amplifier, and the inverting input terminal of the second amplifier is connected to the output terminal of the second amplifier; the non-inverting input terminal of the second amplifier is connected to the bias temperature compensation module, and the other end of the bias temperature compensation module is grounded.

[0041] In one embodiment, please refer to Figure 3 and Figure 4 , a resistor Rf is also connected between the sensitivity temperature compensation module and the inverting input terminal of the first amplifier.

[0042] In one embodiment, please refer to Figure 3 and Figure 4 , a resistor R2 is also connected to the non-inverting input terminal of the second amplifier.

[0043] In one embodiment, please refer to Figure 3 , the sensitivity temperature compensation module includes a thermistor Rt1, and the bias temperature compensation module includes a thermistor Rt2.

[0044] Specifically, the temperature drift of the output curve can be compensated by the thermistor. According to circuit calculation, the output function of the sensor after temperature compensation can be obtained: When the temperature changes, the resistance value of the thermistor changes. Let Rt1 become Rt1 + Δ rt1 、Rt2 become Rt2 + Δ rt2, substituting into the function to obtain the output function after temperature change: When R2 + Rt2 >> Rt2, the above function can be changed to: Let Substituting into the above function, the output function after temperature compensation is: After the temperature changes, temperature drift occurs and its output function becomes Therefore, when the output temperature drift is cancelled out, that is, the output becomes y(x) = ax + b.

[0045] In another embodiment, since the temperature drift changes generated by the sensor and the temperature drift changes of the thermistor cannot be completely cancelled out in different temperature ranges, digital temperature compensation can be used to replace the thermistor with a digital potentiometer.

[0046] Please refer to Figure 4 , the above sensitivity temperature compensation module includes a first digital potentiometer; the bias temperature compensation module includes a second digital potentiometer.

[0047] In another embodiment, please refer to Figure 4 , the above first digital potentiometer and second digital potentiometer are respectively connected to a digital temperature compensation controller.

[0048] In another embodiment, please refer to Figure 4 , the above digital temperature compensation controller is connected to a temperature sensor.

[0049] In another embodiment, please refer to Figure 4 , the above digital temperature compensation controller is used to divide the temperature change range into several small ranges, set the sensitivity temperature compensation coefficient and bias voltage compensation coefficient in each different range, obtain the current temperature measured by the temperature sensor in real time, determine the sensitivity temperature compensation coefficient and bias voltage compensation coefficient according to the current temperature, and correspondingly set the coefficients corresponding to the first digital potentiometer and the second digital potentiometer, so that the temperature drift in different temperature ranges can be compensated more precisely.

[0050] Specifically, the digital temperature compensation controller is connected to the temperature sensor for obtaining the current ambient temperature in real time; the digital temperature compensation controller divides the entire temperature range into multiple small ranges.

[0051] Interval setting: Within each small interval, the digital temperature compensation controller sets different sensitivity temperature compensation coefficients and bias voltage compensation coefficients. The setting of these coefficients is based on previous calibration and experimental data to ensure that within each temperature interval, the output of the sensor can be accurately adjusted and calibrated.

[0052] In the sensitivity temperature compensation module, the first digital potentiometer is used to adjust the amplification factor according to the sensitivity compensation coefficient within the current interval. This can eliminate the sensitivity change caused by temperature variation. In the bias temperature compensation module, the second digital potentiometer adjusts the bias voltage according to the bias voltage compensation coefficient within the current interval. This ensures that even under different temperature conditions, the output bias of the sensor can remain within the expected range.

[0053] Through digital temperature compensation, the system can dynamically adjust the parameters of the sensor under different temperature conditions to eliminate the influence of temperature drift, thereby improving the measurement accuracy and stability. The digital temperature compensation controller can monitor and adjust in real time to ensure that even when the ambient temperature changes, the system can quickly respond and make corresponding compensations to maintain the accuracy of the sensor. Since the temperature range is divided into multiple small intervals and specific compensation parameters are set within each interval, the system can more flexibly adapt to various complex working environments and temperature change conditions.

[0054] In summary, this digital temperature compensation technology not only solves the problems of sensitivity and bias drift of the sensor caused by temperature change, but also improves the reliability and measurement accuracy of the system, and is applicable to application scenarios requiring high precision and stability, such as industrial automation, environmental monitoring and other fields.

[0055] Such as Figure 5 and Figure 6 shown, the output after temperature compensation can ensure stability and accuracy.

[0056] For the above-mentioned eddy current sensor temperature compensation circuit, an AC signal is generated by the excitation source 10. After being processed by the LC resonance unit 20, the detection unit 30, the filtering unit 40 and the amplification unit 50, the temperature compensation unit 60 is used to perform sensitivity and bias compensation on the output signal to offset the influence of temperature change on the performance of the sensor, so as to realize the compensation for the sensitivity temperature drift and bias temperature drift of the output of the eddy current sensor and ensure the stability and accuracy of the output of the eddy current sensor.

[0057] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A temperature compensation circuit for an eddy current sensor, characterized in that: include: An excitation source, an LC resonance unit, a detection unit, a filtering unit, an amplifying unit and a temperature compensation unit; the excitation source is connected to the LC resonance unit; the LC resonance unit is sequentially connected to a detection unit, a filtering unit and an amplifying unit; the temperature compensation unit is connected to the amplifying unit; wherein the excitation source is used to input an AC signal; the LC resonance unit is used to form a resonance according to the AC signal; the detection unit is used to modulate the resonant AC signal into a DC signal; the filtering unit is used to filter the DC signal; the amplifying unit is used to amplify the filtered DC signal and then output it; the temperature compensation unit is used to compensate for the drift of the sensitivity of the signal output by the amplifying unit under temperature changes and to compensate for the drift of the bias of the input signal of the amplifying unit under temperature changes.

2. The eddy current sensor temperature compensation circuit according to claim 1, characterized in that: The temperature compensation unit includes a sensitivity temperature compensation module and a bias temperature compensation module, the amplification unit includes an amplification circuit with a variable amplification factor; the sensitivity temperature compensation module is connected to the output end of the amplification circuit; the bias temperature compensation module is connected to the input end of the amplification circuit.

3. The eddy current sensor temperature compensation circuit according to claim 2, characterized in that: The amplification circuit includes a first amplifier and a second amplifier, the inverting input terminal of the first amplifier is connected to the filtering unit; the sensitivity temperature compensation module is connected between the output terminal of the first amplifier and the inverting input terminal of the first amplifier, the non-inverting input terminal of the first amplifier is connected to the output terminal of the second amplifier, and the inverting input terminal of the second amplifier is connected to the output terminal of the second amplifier; the non-inverting input terminal of the second amplifier is connected to the bias temperature compensation module, and the other end of the bias temperature compensation module is grounded.

4. The eddy current sensor temperature compensation circuit according to claim 3, characterized in that: A resistor Rf is further connected between the sensitivity temperature compensation module and the inverting input terminal of the first amplifier.

5. The eddy current sensor temperature compensation circuit according to claim 4, characterized in that: The non-inverting input terminal of the second amplifier is further connected to a resistor R2.

6. The eddy current sensor temperature compensation circuit according to claim 5, characterized in that: The sensitivity temperature compensation module includes a thermistor Rt1, and the bias temperature compensation module includes a thermistor Rt2.

7. The eddy current sensor temperature compensation circuit according to claim 5, characterized in that: The sensitivity temperature compensation module includes a first digital potentiometer; the bias temperature compensation module includes a second digital potentiometer.

8. The eddy current sensor temperature compensation circuit according to claim 7, characterized in that: The first digital potentiometer and the second digital potentiometer are respectively connected to a digital temperature compensation controller.

9. The eddy current sensor temperature compensation circuit according to claim 8, characterized in that: The digital temperature compensation controller is connected to a temperature sensor.

10. The eddy current sensor temperature compensation circuit according to claim 9, characterized in that: The digital temperature compensation controller is used to divide the temperature change interval into several small intervals, set the sensitivity temperature compensation coefficient and the bias voltage compensation coefficient in each different interval, obtain the current temperature measured by the temperature sensor in real time, determine the sensitivity temperature compensation coefficient and the bias voltage compensation coefficient according to the current temperature, and set the coefficients corresponding to the first digital potentiometer and the second digital potentiometer accordingly.

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