Inductive displacement sensor probe temperature drift compensation circuit

Abstract

The application provides an inductive displacement sensor probe temperature drift compensation circuit, which comprises a probe coil, a probe sensitive resistor connected with the probe coil, and a high-frequency signal source for exciting the probe coil through the probe sensitive resistor; further comprising a direct current reference voltage and a superposition amplifier; the superposition amplifier is configured to superimpose alternating current and direct current signals after the direct current reference voltage and the high-frequency signal source are isolated by a direct current isolation capacitor; the superposition amplifier is further configured to excite the probe coil through the superimposed alternating current and direct current signals. In the above technical solution, no modification is needed for the ordinary conventional sensor probe. The temperature drift of the direct current impedance of the probe coil and the thermal expansion drift of the structure constituting the probe component can be compensated at the same time, and the measurement effect is improved.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a temperature drift compensation circuit for an inductive displacement sensor probe. Background Technology

[0002] When inductive displacement sensors measure displacement / vibration in high-temperature environments, especially ultra-high and ultra-low temperature environments, the DC impedance of the probe coil changes with temperature. This causes changes in the sensor's sensitivity, range, and linearity, leading to measurement errors. Additionally, because the components of the probe have different coefficients of thermal expansion, the physical gap between the probe head and the target object changes with temperature due to the influence of these coefficients, resulting in deviations in the measurement data.

[0003] Existing probe temperature drift compensation technologies mainly employ two methods: installing a temperature sensor inside the probe and using a dual-coil structure, with one coil serving as the temperature compensation coil.

[0004] In temperature compensation methods that use a temperature sensor installed inside the probe, the temperature drift curve of the probe coil and the temperature drift curve of the temperature sensor are unlikely to match, resulting in limited temperature compensation effectiveness. Furthermore, this compensation scheme does not consider the different thermal expansion coefficients of the probe components, or that the probe material changes with temperature, causing variations in the probe's physical length. This affects the actual physical gap between the probe and the target object, leading to temperature deviations in the measurement results.

[0005] In the dual-coil structure method, the probe structure is complex and the external size of the probe cannot be reduced. The compensation is only good at the midpoint of the measurement range. Similarly, this compensation scheme does not take into account the different thermal expansion coefficients of the components of the probe, the changes in the probe material due to temperature changes that affect the physical length of the probe itself, thus affecting the actual physical gap between the probe and the target object, and causing the measurement results to deviate with changes in ambient temperature. Summary of the Invention

[0006] This application provides a temperature drift compensation circuit for an inductive displacement sensor probe, which improves the measurement effect.

[0007] This application provides a temperature drift compensation circuit for an inductive displacement sensor probe. The inductive displacement sensor probe temperature drift compensation circuit includes: a probe coil, a probe sensitive resistor connected to the probe coil, and a high-frequency signal source that excites the probe coil through the probe sensitive resistor.

[0008] It also includes a DC reference voltage and a superposition amplifier; the superposition amplifier is configured to superimpose AC / DC signals on the DC reference voltage and the high-frequency signal source after isolation by a DC blocking capacitor; the superposition amplifier is also configured to excite the probe coil by the superimposed AC / DC signals.

[0009] The above technical solution requires no modification to conventional sensor probes. It can simultaneously compensate for the temperature drift of the probe coil's DC impedance and the thermal expansion drift of the structural components constituting the probe, thereby improving measurement performance.

[0010] In one specific implementation, a temperature-sensitive resistor is further included, configured between the superimposed amplifier and the probe coil; the superimposed amplifier drives the probe coil through the temperature-sensitive resistor.

[0011] In a specific feasible implementation, it also includes:

[0012] A filtering circuit configured to filter the displacement / temperature composite signal in the output signal of the superimposed amplifier;

[0013] A detection circuit configured to detect a filtered displacement / temperature composite signal;

[0014] Probe coil DC impedance extraction circuit: The probe coil DC impedance extraction circuit is configured to isolate and extract the DC impedance signal of the probe coil.

[0015] In one specific implementation, the detection circuit is a peak detection circuit, a peak-to-peak detection circuit, an RMS detection circuit, a lock-in amplifier detection circuit, or a phase-sensitive detection circuit.

[0016] In one specific implementation, the probe coil DC impedance extraction circuit includes an integrating resistor and a low-pass filter capacitor; the integrating resistor and the low-pass filter capacitor C2 are configured to isolate and extract the probe signal of the coil temperature DC impedance signal and then send the coil temperature DC impedance signal to the DC impedance signal amplifier after low-pass filtering.

[0017] In one specific implementation, a coil DC impedance temperature drift compensation circuit is also included, which is configured to perform a subtraction operation on the displacement / temperature composite signal from the detector and the probe coil DC impedance signal from the DC impedance signal amplifier to eliminate the DC impedance temperature drift of the probe coil.

[0018] In one specific implementation scheme, it further includes: a displacement signal conditioning circuit and a probe thermal expansion compensation circuit, wherein the displacement signal conditioning circuit is configured to amplify, filter, and normalize the signal from the coil DC impedance temperature drift compensation circuit;

[0019] The probe thermal expansion compensation circuit is configured to perform addition and subtraction operations on signals from the displacement signal conditioning circuit and the coil DC impedance amplifier to compensate for temperature drift caused by probe thermal expansion.

[0020] In one specific implementation, the displacement signal conditioning circuit includes a sensor linearity correction circuit and an amplification and normalization circuit.

[0021] In one specific implementation, the superimposed amplifier is a voltage follower or a finite gain amplifier.

[0022] In one specific implementation, the temperature-sensitive resistor is a pure resistor or an impedance network consisting of RC or RLC circuits. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the temperature drift compensation circuit for the inductive displacement sensor probe provided by the present invention.

[0024] Figure 2 This is a schematic diagram of another inductive displacement sensor probe temperature drift compensation circuit provided by the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the application will now be described in further detail with reference to the accompanying drawings.

[0026] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of this specification should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar words used in one or more embodiments of this specification do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0027] refer to Figure 1This application provides a temperature drift compensation circuit for an inductive displacement sensor probe. Due to the structural characteristics of the inductive displacement sensor, the temperature drift of the probe includes the sensitivity temperature drift of the probe coil and the thermal expansion drift of the various components constituting the probe. The DC impedance of the probe coil has a fixed proportional relationship with the temperature change, and the ambient temperature of the probe coil can be measured by measuring the DC impedance of the probe coil.

[0028] In this embodiment, the inductive displacement sensor probe temperature drift compensation circuit includes: a probe coil L1, a probe sensitive resistor R2 connected to the probe coil L1, and a high-frequency signal source that excites the probe coil L1 through the probe sensitive resistor R2; it also includes a DC reference voltage and a superposition amplifier IC1; the superposition amplifier IC1 is configured to superimpose the AC / DC signal after isolating the DC reference voltage and the high-frequency signal source through a DC blocking capacitor; the superposition amplifier IC1 is also configured to excite the probe coil L1 through the superimposed AC / DC signal.

[0029] In this configuration, a high-frequency signal source drives the probe coil L1 through the probe sensitivity resistor R2. For example, the probe coil L1 is excited by the high-frequency signal source S1 through the probe sensitivity resistor R2. Adjusting the value of the probe sensitivity resistor R2 changes the probe's sensitivity. O1 represents the high-frequency source excitation current signal for the probe coil L1.

[0030] In this embodiment, the temperature drift compensation circuit further includes a temperature-sensitive resistor R configured between the superposition amplifier and the probe coil: the superposition amplifier drives the probe coil through the temperature-sensitive resistor. For example, the superposition amplifier IC1 superimposes the DC reference voltage REF1 and the high-frequency signal applied to the probe coil L1, and then drives the probe coil L1 through the temperature-sensitive resistor R3. Specifically, the superposition amplifier IC1 isolates the DC reference voltage REF1 and the high-frequency voltage signal on the probe coil L1 through the DC blocking capacitor C1, performs AC / DC signal superposition, and then drives the probe coil L1 through the temperature-sensitive resistor R3. I2 is the excitation current signal superimposed from the high-frequency source and the DC source of the superposition amplifier IC1 driving the probe coil L1 through R3. The superposition amplifier includes, but is not limited to, a voltage follower and a finite gain amplifier.

[0031] The temperature-sensitive resistor R3 has two functions: first, it forms a DC voltage divider circuit with the inherent DC impedance of the probe coil L1, outputting a DC voltage signal proportional to the temperature at the positive terminal of the coil; second, it provides the probe coil L1 with a high-frequency excitation signal that is in the same source and phase as the high-frequency excitation signal, thereby improving the sensitivity of the probe. In the embodiments of this application, the temperature-sensitive resistor R3 includes, but is not limited to, a pure resistor, and an impedance network composed of RC or RLC circuits.

[0032] The temperature drift compensation circuit provided in this embodiment further includes a filtering circuit and a detection circuit. The filtering circuit is configured to filter the displacement / temperature composite signal in the output signal of the superposition amplifier; the detection circuit is configured to detect the filtered displacement / temperature composite signal. In use, the output signal of the superposition amplifier IC1 is fed into the filtering circuit U1 for DC blocking filtering of the displacement / temperature composite signal, then sent to the detector U2 for detection, and finally the displacement / temperature composite signal enters the coil DC impedance temperature drift compensation circuit IC2.

[0033] In the embodiments of this application, the detection circuit U2 includes, but is not limited to, peak detection circuit, peak-to-peak detection circuit, RMS detection circuit, lock-in amplifier detection circuit, and phase-sensitive detection circuit.

[0034] As an optional solution, in this embodiment, the AC voltage output value of the superposition amplifier IC1 is consistent with or proportional to the value of the probe coil L1. The aforementioned fixed proportion can be adjusted by changing the gain of IC1 based on actual temperature drift detection data to achieve the desired design requirements.

[0035] The filter circuit U1 separates the displacement / temperature composite signal from the signal output from the superposition amplifier IC1 by DC blocking, then filters the displacement / temperature composite signal, and finally inputs it to the detector circuit U2 for displacement / temperature composite signal detection. The detected displacement / temperature composite signal is then input to the coil DC impedance temperature drift compensation circuit IC2.

[0036] In this embodiment, the temperature drift compensation circuit further includes a coil DC impedance extraction circuit, which is configured to isolate and extract the DC impedance signal of the probe coil. Specifically, the coil DC impedance extraction circuit includes an integrating resistor and a low-pass filter capacitor; the integrating resistor R4 and the low-pass filter capacitor C2 are configured to isolate and extract the coil temperature DC impedance signal of the probe signal and then low-pass filter it before sending the coil temperature DC impedance signal to the DC impedance signal amplifier U3. Specifically, the integrating resistor R4 and the low-pass filter capacitor C2 isolate and extract the coil temperature DC impedance signal of the probe signal and then low-pass filter it before sending the coil temperature DC impedance signal to the DC impedance signal amplifier U3. It should be understood that the integrating resistor R4 and the low-pass filter capacitor C2 isolate and extract the coil temperature DC impedance signal of the probe signal and then low-pass filter it before sending the coil temperature DC impedance signal to the DC impedance signal amplifier U3.

[0037] In this embodiment, the temperature drift compensation circuit further includes a coil DC impedance temperature drift compensation circuit. This circuit is configured to subtract the displacement / temperature composite signal from the detector from the probe coil's DC impedance signal from the DC impedance signal amplifier, thereby eliminating the DC impedance temperature drift of the probe coil. For example, the coil DC impedance temperature drift compensation circuit IC2 subtracts the displacement / temperature composite signal from the detector U2 from the DC impedance signal amplifier U3, outputting a displacement signal independent of temperature changes and sending it to the displacement signal conditioning circuit U4. Specifically, the coil DC impedance temperature drift compensation circuit IC2 subtracts the displacement / temperature composite signal from the detector U2 from the probe coil's DC impedance signal I4 from the DC impedance signal amplifier U3 to eliminate the DC impedance temperature drift of the probe coil.

[0038] The temperature drift compensation circuit provided in this embodiment further includes a displacement signal conditioning circuit and a probe thermal expansion compensation circuit. The displacement signal conditioning circuit is configured to amplify, filter, and normalize the signal from the coil DC impedance temperature drift compensation circuit; while the probe thermal expansion compensation circuit is configured to perform addition and subtraction operations on the signals from the displacement signal conditioning circuit and the coil DC impedance amplifier to compensate for the temperature drift caused by the thermal expansion of the probe. For example, the displacement signal conditioning circuit U4 amplifies, filters, and normalizes the signal from the coil DC impedance temperature drift compensation circuit IC2, and then sends it to the probe thermal expansion compensation circuit IC3. The probe thermal expansion compensation circuit IC3 performs addition and subtraction operations on the displacement signal from the displacement signal conditioning circuit U4 and the temperature DC impedance signal from the DC impedance signal amplifier U3 to compensate for the thermal expansion drift of the probe, obtaining a pure gap displacement signal independent of temperature.

[0039] Specifically, the displacement signal conditioning circuit U4 includes, but is not limited to, various sensor linear correction circuits such as linear amplification, logarithmic linear correction, digital circuit interpolation linear correction, and high-order analog linear correction, as well as amplification and normalization circuits.

[0040] The probe thermal expansion compensation circuit IC3 performs addition and subtraction operations on the signal O3 from the displacement signal conditioning circuit and the coil DC impedance amplifier U3 to compensate for the temperature drift caused by the thermal expansion of the probe.

[0041] The aforementioned temperature drift compensation circuit also includes a temperature normalization circuit. Temperature normalization circuit U5 normalizes the DC impedance-temperature change characteristic output by DC impedance signal amplifier U3, outputting a temperature signal that is linear with temperature change. For example, temperature normalization circuit U5 normalizes the DC impedance-temperature change signal I5 output by DC impedance signal amplifier U3, outputting a temperature signal that is linear with temperature change.

[0042] It should be understood that the probe coil DC impedance signal I3, probe coil DC impedance signal I4, and DC impedance-temperature change signal I5 mentioned above are actually the same probe coil temperature DC impedance signal output by the DC impedance signal amplifier U3.

[0043] refer to Figure 2 , Figure 2 As another variation of the temperature drift compensation circuit for an inductive displacement sensor probe, the DC reference voltage REF1 passes through R1 to DC amplifier IC1-1, and then excites the probe coil L1 through temperature sensitivity resistor R3. The probe signal is buffered and amplified by buffer amplifier IC1-2 after passing through DC blocking capacitor C1, and then sent to filter circuit U1. Figure 1 It achieves the same effect, but the probe sensitivity of this solution is higher than... Figure 1 A smaller sensor size will reduce the sensor's resolution and signal-to-noise ratio.

[0044] As can be seen from the above solution, the temperature drift compensation circuit provided in this application embodiment requires no modification to a conventional sensor probe. It can simultaneously compensate for the temperature drift of the probe coil's DC impedance and the thermal expansion drift of the structures constituting the probe components, thereby improving measurement performance.

[0045] One or more embodiments of this specification are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments of this specification should be included within the scope of protection of this disclosure.

[0046] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A temperature drift compensation circuit for an inductive displacement sensor probe, characterized in that, include: The probe coil, the probe sensing resistor connected to the probe coil, and the high-frequency signal source that excites the probe coil through the probe sensing resistor; It also includes a DC reference voltage and a superposition amplifier; the superposition amplifier is configured to superimpose AC / DC signals from the DC reference voltage and the high-frequency signal source after isolation by a DC blocking capacitor; the superposition amplifier is further configured to excite the probe coil through the superimposed AC / DC signal; the superposition amplifier is a voltage follower or a finite gain amplifier; wherein, The AC voltage output value of the superimposed amplifier is consistent with or in a fixed proportion to the value of the probe coil; It also includes a filtering circuit connected to the superimposed amplifier, the filtering circuit being configured to filter the displacement / temperature composite signal in the output signal of the superimposed amplifier; It also includes a detection circuit connected to the filtering circuit, the detection circuit being configured to detect the filtered displacement / temperature composite signal; It also includes a probe coil DC impedance extraction circuit, which is configured to isolate and extract the DC impedance signal of the probe coil. The probe coil DC impedance extraction circuit includes an integrating resistor and a low-pass filter capacitor; the integrating resistor and the low-pass filter capacitor are configured to isolate and extract the probe signal of the coil temperature DC impedance signal and then send the coil temperature DC impedance signal into the DC impedance signal amplifier after low-pass filtering. It also includes a coil DC impedance temperature drift compensation circuit, which is configured to perform a subtraction operation on the displacement / temperature composite signal from the detector and the probe coil DC impedance signal from the DC impedance signal amplifier to eliminate the DC impedance temperature drift of the probe coil. It also includes a displacement signal conditioning circuit and a probe thermal expansion compensation circuit connected to the probe coil DC impedance extraction circuit. The displacement signal conditioning circuit is configured to amplify, filter, and normalize the signal from the coil DC impedance temperature drift compensation circuit. The probe thermal expansion compensation circuit is configured to perform addition and subtraction operations on the signals from the displacement signal conditioning circuit and the coil DC impedance amplifier to compensate for the temperature drift caused by the thermal expansion of the probe.

2. The temperature drift compensation circuit for the inductive displacement sensor probe according to claim 1, characterized in that, It also includes a temperature-sensitive resistor configured between the superimposed amplifier and the probe coil; the superimposed amplifier drives the probe coil through the temperature-sensitive resistor.

3. The temperature drift compensation circuit for the inductive displacement sensor probe according to claim 1, characterized in that, The detection circuit is a peak detection circuit, a peak-to-peak detection circuit, an RMS detection circuit, a lock-in amplifier detection circuit, or a phase-sensitive detection circuit.

4. The temperature drift compensation circuit for the inductive displacement sensor probe according to claim 1, characterized in that, The displacement signal conditioning circuit includes a sensor linear correction circuit and an amplification and normalization circuit.

5. The temperature drift compensation circuit for the inductive displacement sensor probe according to claim 2, characterized in that, The temperature-sensitive resistor is a pure resistor or an impedance network composed of RC or RLC circuits.

Images