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CN-122015622-A - Precise capacitance micrometer system and micrometer method

CN122015622ACN 122015622 ACN122015622 ACN 122015622ACN-122015622-A

Abstract

The application discloses a precise capacitance micrometer system which comprises a modulation signal source, a sensitive probe, a differential transformer bridge circuit, a signal amplification link, a multiplier and a low-pass filter circuit which are electrically connected in sequence, wherein a double-limit comparator is arranged between the signal amplification link and the multiplier, the input end of the double-limit comparator is connected with the output end of the signal amplification link, and the output end of the double-limit comparator is connected with one input end of the multiplier and is used for shaping an amplified modulation signal and taking the shaped signal as a demodulation input signal. The application also provides a precise capacitance micrometer method. The precise capacitance micrometer system provided by the embodiment of the application ensures that the system output is insensitive to phase difference fluctuation in a certain demodulation phase difference range, and finally realizes the high-precision measurement of micro displacement. All modules complete full-link conversion from physical quantity to measurable voltage signal through step-by-step transmission and functional complementation of signals.

Inventors

  • LI KE
  • YUAN BIN

Assignees

  • 中国人民解放军信息支援部队工程大学

Dates

Publication Date
20260512
Application Date
20251231

Claims (10)

  1. 1. A precise capacitance micrometer system comprises a modulation signal source, a sensitive probe, a differential transformer bridge circuit, a signal amplifying link, a multiplier and a low-pass filter circuit which are electrically connected in sequence, The modulating signal source is used for generating a sine carrier signal, the sensitive probe comprises a testing quality and an upper polar plate and a lower polar plate which form a differential capacitor with the testing quality, the sensitive probe is used for converting micro-displacement into a differential capacitor signal, the differential transformer bridge is connected with the differential capacitor through a primary coil to form a balanced bridge, the differential transformer bridge is used for modulating the differential capacitor signal onto the sine carrier and outputting a modulating voltage signal, the signal amplifying link is connected with the differential transformer bridge and used for amplifying and noise suppressing the modulating voltage signal, and the multiplier is used for receiving a demodulation input signal and a demodulation reference signal, performing multiplication demodulation operation and outputting a demodulation signal; The low-pass filter circuit is connected with the output end of the multiplier and is used for filtering high-frequency components in demodulation signals generated by multiplication and demodulation operations, and extracting direct-current voltage signals in direct proportion to the micro-displacement as system output; The device is characterized by further comprising a double-limit comparator arranged between the signal amplification link and the multiplier, wherein the input end of the double-limit comparator is connected with the output end of the signal amplification link, and the output end of the double-limit comparator is connected to one input end of the multiplier and is used for shaping an amplified modulation signal and taking the shaped signal as the demodulation input signal.
  2. 2. The precision capacitance micrometer system according to claim 1, wherein the double-limit comparator comprises a threshold comparison unit and a 2-to-1 analog switch; The threshold comparison unit is used for judging whether the amplitude of the input signal exceeds a section defined by an upper threshold voltage and a lower threshold voltage; The 2-to-1 analog switch is controlled by the output of the threshold comparison unit, outputs a signal consistent with the input signal when the input signal amplitude is outside the interval defined by the upper threshold voltage and the lower threshold voltage, and outputs a zero-level signal when the input signal amplitude is within the interval defined by the upper threshold voltage and the lower threshold voltage.
  3. 3. The precision capacitance micrometer system according to claim 2, wherein the threshold comparison unit comprises a two-way differential comparator connected to the upper threshold voltage and the lower threshold voltage, respectively, the output of the two-way differential comparator being logically combined with the upper threshold voltage and the lower threshold voltage by a diode or a logic gate circuit to generate a control signal for transmission to the control terminal of the 2-to-1 analog switch.
  4. 4. The precision capacitance micrometer system according to claim 2, wherein the threshold comparison unit comprises an analog-to-digital converter and a programmable gate array or a microprocessor, wherein the analog-to-digital converter is used for collecting analog signals output by the signal amplification link, and the programmable logic device or the microprocessor is used for comparing the digitized signal amplitude with the upper threshold voltage and the lower threshold voltage to generate corresponding control signals for transmission to a control terminal of the 2-to-1 analog switch.
  5. 5. The precision capacitance micrometer system according to claim 1, wherein the signal amplification link is a three-stage cascade amplification circuit comprising a front-end amplification circuit, a differential amplification circuit, and an ac amplification circuit electrically connected in sequence: The front-end amplifying circuit is used for amplifying the modulated voltage signal output by the differential transformer bridge circuit and inhibiting input stage noise; the differential amplifying circuit is used for amplifying differential signals related to displacement and inhibiting common mode noise; The alternating current amplifying circuit is used for amplifying signals near carrier frequency and inhibiting noise outside the bandwidth.
  6. 6. The precision capacitance micrometer system according to claim 1, wherein the multiplier is a switched multiplier, and the demodulation reference signal is a waveform of the same frequency as the sine carrier and symmetrical up and down.
  7. 7. The precision capacitance micrometer system according to any one of claims 1-6, wherein the upper threshold voltage and the lower threshold voltage are equal in absolute value and have a magnitude lower than a magnitude of the ac amplifying circuit output signal.
  8. 8. A precision capacitance micrometer system according to claim 3 wherein the two-way differential comparator is built up as an integrated or discrete component.
  9. 9. A precision capacitance micrometer method comprising: S100, generating a sine carrier signal by using a modulation signal source; S200, detecting capacitive micro-displacement through a sensitive probe, and converting the micro-displacement into a differential capacitive signal; s300, modulating the differential capacitance signal onto the sine carrier wave and outputting a modulated voltage signal; s400, amplifying and noise suppressing the modulated voltage signal, inputting the amplified signal into a multiplier for multiplication and demodulation operation, and outputting a demodulation signal; S500, filtering high-frequency components in demodulation signals generated by multiplication and demodulation operations through a low-pass filter circuit, and extracting direct-current voltage signals proportional to the micro-displacement to be used as system output; The method is characterized in that after the modulated voltage signal is amplified and noise-suppressed and before the modulated voltage signal is input into a multiplier, a double-limit comparator is further arranged to shape the amplified and noise-suppressed modulated signal, and the shaped modulated signal is input into the multiplier as a demodulation input signal.
  10. 10. The precise capacitance micrometer method according to claim 9, wherein the setting the double limit comparator shapes the amplified and noise-suppressed modulated signal, specifically comprising: Comparing the instantaneous amplitude of the amplified modulation signal with a preset upper threshold voltage and a preset lower threshold voltage in real time, setting a control signal to a first state when the instantaneous amplitude of the amplified modulation signal is larger than the upper threshold voltage or smaller than the lower threshold voltage, and setting the control signal to a second state when the instantaneous amplitude of the amplified modulation signal is not larger than the upper threshold voltage and not smaller than the lower threshold voltage; And selecting an output signal through an analog switch based on the state of the control signal, wherein when the control signal is in a first state, a waveform which is consistent with the amplified modulation signal and output by the analog switch is used as a demodulation input signal, and when the control signal is in a second state, the signal output by the analog switch is set as a zero level signal and is used as the demodulation input signal.

Description

Precise capacitance micrometer system and micrometer method Technical Field The application relates to the technical field of precise measurement, in particular to a precise capacitance micrometer system and a micrometer method. Background The basic principle of the capacitance micrometric technology as a high-precision non-contact measurement method is to invert displacement by detecting capacitance change caused by micro displacement of an object to be measured. The technology has the outstanding advantages of high sensitivity, good stability, quick dynamic response, relatively simple structure and the like, and is widely applied to scenes with extreme requirements on measurement precision, such as core sensing instruments of a gravity meter, a seismometer, a gyroscope, an accelerometer and the like. In these applications, the measurement system often needs to maintain stable and reliable performance under complex working conditions such as large temperature variation and electromagnetic interference, so improving the anti-interference capability and long-term stability of the capacitance micrometer system is always an important research direction of those skilled in the art. At present, a differential transformer bridge structure based on sine carrier modulation and demodulation has become a main technical scheme for realizing high-precision capacitance micrometer, and the scheme provides favorable conditions for subsequent signal amplification and noise suppression by modulating a low-frequency displacement signal onto a high-frequency carrier. In the prior art solutions, the demodulation step usually requires a multiplication of a reference signal (e.g. square wave) of the same frequency as the carrier wave with the modulated input signal. However, there is inevitably a phase difference θ between the demodulation reference signal and the input signal. Theoretical analysis and practice show that the final output of the system is directly proportional to cos theta, which means that any micro fluctuation of phase difference theta caused by ambient temperature drift, element parameter variation or signal transmission path difference can be directly converted into measurement error of the system output, and further improvement of measurement accuracy is severely restricted. To overcome this drawback, a method of using quadrature demodulation to suppress the influence of phase difference fluctuation has been proposed in the prior art. However, the implementation structure of the method is complex, quadrature errors can be introduced, the gain and phase symmetry of a quadrature channel and an in-phase channel in a demodulation circuit are highly dependent, ideal performance is difficult to achieve and maintain for a long time in practical engineering application, the complexity and cost of a system are increased, and the practical anti-interference effect is difficult to be effectively ensured. Therefore, a demodulation scheme which has a relatively simple structure, is insensitive to phase difference fluctuation and has stable performance is sought, and the technical problem to be solved in the field is urgent. Disclosure of Invention In response to at least one of the foregoing needs and improvements, the present application provides a precision capacitive micrometer system and method that address at least one of the problems set forth in the background. To achieve the above object, according to a first aspect of the present application, there is provided a precision capacitance micrometer system comprising a modulating signal source, a sensitive probe, a differential transformer bridge, a signal amplifying link, a multiplier and a low-pass filter circuit electrically connected in this order, wherein, The modulating signal source is used for generating a sine carrier signal, the sensitive probe comprises a testing quality and an upper polar plate and a lower polar plate which form a differential capacitor with the testing quality, the sensitive probe is used for converting micro-displacement into a differential capacitor signal, the differential transformer bridge is connected with the differential capacitor through a primary coil to form a balanced bridge, the differential transformer bridge is used for modulating the differential capacitor signal onto the sine carrier and outputting a modulating voltage signal, the signal amplifying link is connected with the differential transformer bridge and used for amplifying and noise suppressing the modulating voltage signal, and the multiplier is used for receiving a demodulation input signal and a demodulation reference signal, performing multiplication demodulation operation and outputting a demodulation signal; The low-pass filter circuit is connected with the output end of the multiplier and is used for filtering high-frequency components in demodulation signals generated by multiplication and demodulation operations, and extracting direct-current voltage sign