Compensation method of vibration capacitance type electrostatic sensor

Abstract

The invention discloses a compensation method for a vibration capacitance type electrostatic sensor, and the method comprises the steps: detecting the temperature of an environment where the current electrostatic sensor is located, enabling a sensitive piece signal to serve as an input value after amplification and filtering, obtaining a sensor output value through a linear temperature compensation function, and achieving the low calculation amount and convenient integration; a temperature compensation method comprises the following steps: detecting the temperature of an environment where a current electrostatic sensor is located, loading a sinusoidal signal of a reference resonant frequency corresponding to the temperature to a first piezo-electric crystal, and detecting a feedback signal peak value of a second piezo-electric crystal, so that a tuning fork always vibrates at a natural vibration frequency, and the adaptability of the electrostatic sensor to the environment temperature is improved; according to the induction distance compensation method, the vertical distance between a current electrostatic sensor and the surface of a detected object is detected, a sensitive piece signal is amplified and filtered to serve as an input value, a sensor output value is obtained through a linear induction distance compensation function, the calculated amount is low, and integration is convenient.

Description

Technical Field

[0001] The invention relates to the technical field of electrostatic monitoring, and in particular to a compensation method for a vibrating capacitive electrostatic sensor. Background Art

[0002] Electrostatic discharge has the characteristics of high potential, large transient current and difficulty in observation. If not properly protected, it can cause hazards such as increased semiconductor production defect rates and explosion of combustible materials.

[0003] Electrostatic monitoring is an effective means of electrostatic protection and is widely used in semiconductors, medicine, chemicals and other fields. Electrostatic sensors are the core of electrostatic monitoring. According to the measurement principle, they can be divided into direct induction, rotary vane and vibration capacitance types. Direct induction electrostatic sensors use a high input impedance DC amplifier circuit for measurement. During the measurement process, the induced charge on the induction electrode decays over time in the amplifier circuit, resulting in unstable measurement results. Regular zeroing is required, which affects the stability of the measurement. Rotary vane electrostatic sensors use micro motors to drive the shielding electrode to rotate, periodically shield the induction electrode, and expose the induction electrode to the electric field periodically, thereby generating an alternating current signal on the induction electrode, ensuring the stability of the measurement. However, there are problems such as unstable motor speed and short life caused by motor wear. Vibration capacitance electrostatic sensors drive the shielding electrode to vibrate periodically through piezoelectric ceramics, so that the induction electrode is periodically exposed to the electric field, thereby generating an alternating current signal on the induction electrode. It has the advantages of small size, light weight and high precision, and is widely used in the field of non-contact electrostatic measurement.

[0004] However, vibration capacitive electrostatic sensing still has the following two problems: First, the vibration capacitive sensor drives the relative area between the sensing electrode and the surface of the object to be measured to change periodically through the inverse piezoelectric effect of piezoelectric ceramics, but the change in ambient temperature affects the piezoelectric constant of the piezoelectric ceramics and the elastic modulus of the shielding electrode, causing the resonant frequency and amplitude of the cantilever beam of the shielding electrode to change, that is, the relative area changes, thereby causing measurement errors. In actual industrial production environments, the ambient temperature often fluctuates within a certain range; second, when the sensing distance between the electrostatic sensor and the surface of the object to be measured changes, the capacitance value formed by the sensing electrode and the surface of the object to be measured changes, thereby changing the sensitivity of the sensor. In actual applications, the sensing distance needs to be manually calibrated, and it is difficult to achieve electrostatic potential measurement on the surface of dynamic objects. Summary of the invention

[0005] The present invention proposes a compensation method for an electrostatic sensor to solve the above technical problems, and performs temperature compensation and sensing distance compensation on a vibrating capacitive electrostatic sensor, aiming to reduce the influence of ambient temperature and sensing distance on the measurement results of the electrostatic sensor and enhance the environmental adaptability of the vibrating capacitive electrostatic sensor.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] According to a first aspect of an embodiment of the present invention, a compensation method for a vibrating capacitive electrostatic sensor is provided, and temperature compensation is performed on the electrostatic sensor based on pre-calibrated parameters, comprising the following steps:

[0008] Step S101, using a temperature sensor to detect the current ambient temperature T of the electrostatic sensor;

[0009] Step S102, the microcontroller controls the digital-to-analog conversion circuit to generate a sinusoidal signal of a reference resonance frequency f0, eliminates the high-frequency component and the DC component in the sinusoidal signal through a first bandpass filter, and forms an excitation signal through a high-voltage amplifier circuit, which is loaded into the first piezoelectric crystal to drive the tuning fork to vibrate periodically;

[0010] Step S103, after the signal of the sensitive chip is amplified and filtered by the preamplifier and the secondary amplifier circuit, the first analog-to-digital conversion circuit converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller;

[0011] Step S104: the microcontroller divides the collected signal amplitude by the total gain of the preamplifier and the secondary amplifier circuit to obtain the value V T As the input value, the output value V is obtained through the linear temperature compensation function. out , as the measurement result of the surface potential of the object being measured.

[0012] Preferably, the reference resonance frequency f0 is the resonance frequency of the tuning fork when it is at an ambient temperature T0, and T0 is a reference temperature for calibrating the output value of the electrostatic sensor.

[0013] As a preferred embodiment, the linear temperature compensation function is V out =V T / K T (T-T0), where K T The value range is -0.0026±0.0004.

[0014] According to a second aspect of an embodiment of the present invention, a compensation method for a vibrating capacitive electrostatic sensor is provided, and temperature compensation is performed on the electrostatic sensor based on active search of a tuning fork resonance frequency, comprising the following steps:

[0015] Step S201, using a temperature sensor to detect the current ambient temperature T of the electrostatic sensor;

[0016] Step S202, the microcontroller controls the digital-to-analog conversion circuit to generate a sinusoidal signal of a reference resonance frequency f0, eliminates the high-frequency component and the DC component in the sinusoidal signal through a first bandpass filter, and forms an excitation signal through a high-voltage amplifier circuit, which is loaded to the first piezoelectric crystal;

[0017] Step S203, after the feedback signal of the second piezoelectric crystal passes through a bandpass filter, the high-frequency component and the low-frequency component in the feedback signal are removed, and after passing through a peak detection circuit, the output peak value of the peak detection circuit is collected by a second analog-to-digital conversion circuit and transmitted to a microcontroller;

[0018] Step S204, if the output peak value deviates from the set amplitude, then within the set frequency range, the microcontroller gradually increases or decreases the excitation signal frequency; if the output peak value exceeds the set amplitude or reaches the upper and lower limits of the set frequency range, the microcontroller decreases or increases the excitation signal frequency until the output peak value returns to the set amplitude;

[0019] Step S205, after the signal of the sensitive chip is amplified and filtered by the preamplifier and the secondary amplifier circuit, the first analog-to-digital conversion circuit converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller;

[0020] Step S206: The microcontroller divides the collected signal amplitude by the total gain of the preamplifier and the secondary amplifier circuit to obtain the value V T As the measurement result of the surface potential of the object being measured.

[0021] Preferably, the first piezoelectric crystal and the second piezoelectric crystal are piezoelectric crystals of the same size and type, and the first piezoelectric crystal and the second piezoelectric crystal are located at the same position of their respective cantilevers.

[0022] Preferably, the reference resonance frequency f0 is the resonance frequency of the tuning fork when it is at an ambient temperature T.

[0023] Preferably, the frequency variation range of the excitation signal is limited to f0±0.1f0.

[0024] According to a third aspect of an embodiment of the present invention, a compensation method for a vibrating capacitive electrostatic sensor is provided, which performs sensing distance compensation on the electrostatic sensor, comprising the following steps:

[0025] Step S301, using a laser distance measuring sensor to detect a vertical distance d between the current electrostatic sensor and the surface of the object being measured;

[0026] Step S302, the microcontroller controls the digital-to-analog conversion circuit to generate a sinusoidal signal of a reference resonance frequency f0, eliminates the high-frequency component and the DC component in the sinusoidal signal through a first bandpass filter, and forms an excitation signal through a high-voltage amplifier circuit, which is loaded to the first piezoelectric crystal;

[0027] Step S303, after the signal of the sensitive chip is amplified and filtered by the preamplifier and the secondary amplifier circuit, the first analog-to-digital conversion circuit converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller;

[0028] Step S304: the microcontroller divides the collected signal amplitude by the total gain of the preamplifier and the secondary amplifier circuit to obtain the value V D As the input value, the output value V is obtained through the linear sensing distance compensation function. out , as the measurement result of the surface potential of the object being measured.

[0029] Preferably, the linear sensing distance compensation function is V out =V D / (K a / d+K c ), where K a The value range of K is 0.0144±0.0006, c The value range is 0.4060±0.0005.

[0030] Compared with the prior art, the electrostatic sensor temperature compensation method based on pre-calibrated parameters of the present invention measures the ambient temperature of the electrostatic sensor and compensates the output value of the electrostatic sensor through a temperature compensation function, so that the electrostatic sensor maintains the same sensitivity coefficient at different ambient temperatures; the electrostatic sensor temperature compensation method based on active search of the tuning fork resonance frequency adjusts the driving signal amplitude of the active piezoelectric crystal according to the vibration amplitude of the passive tuning fork cantilever, so that the tuning fork always vibrates at its natural vibration frequency, so that the electrostatic sensor maintains the same sensitivity coefficient at different ambient temperatures, and improves the adaptability of the electrostatic sensor to ambient temperature; the electrostatic sensor induction distance compensation method measures the vertical distance between the electrostatic sensor and the surface of the object to be measured by a laser sensor and compensates the output value of the electrostatic sensor through induction distance compensation, so that the electrostatic sensor maintains the same sensitivity coefficient at different induction distances, so that the electrostatic sensor can realize the electrostatic potential measurement of the surface of dynamic objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the tuning fork vibration of the vibrating capacitive electrostatic sensor;

[0032] Figure 2 It is a schematic diagram of tuning fork driving and amplitude detection of a vibrating capacitive electrostatic sensor;

[0033] Figure 3 This is a comparison diagram of the excitation signal and feedback signal of the vibration capacitive electrostatic sensor at different temperatures;

[0034] Figure 4 It is a schematic diagram of the output signal of the vibration capacitive electrostatic sensor at different temperatures;

[0035] Figure 5 Schematic diagram of a vibration capacitive electrostatic sensor compensation method according to Embodiment 1 of the present invention;

[0036] Figure 6 Schematic diagram of a vibration capacitive electrostatic sensor compensation method according to Embodiment 2 of the present invention;

[0037] Figure 7 It is a schematic diagram of the output signal of the vibration capacitive electrostatic sensor at different sensing distances;

[0038] Figure 8 Schematic diagram of a vibration capacitive electrostatic sensor compensation method according to Embodiment 3 of the present invention.

[0039] In the figure, 1-first vibration plate, 2-second vibration plate, 3-sensitive plate, 4-first cantilever, 5-second cantilever, 6-support, 7-first piezoelectric crystal, 8-second piezoelectric crystal, 9-first adhesive, 10-second adhesive, 11-high voltage amplifier circuit, 12-first bandpass filter, 13-digital-to-analog conversion circuit, 14-temperature sensor, 15-microcontroller, 16-preamplifier, 17-secondary amplifier circuit, 18-first analog-to-digital conversion circuit, 19-second bandpass filter, 20-peak detection circuit, 21-second analog-to-digital conversion circuit, 22-laser ranging sensor. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on these embodiments are all included in the protection scope of the present invention.

[0041] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the drawings or descriptions, similar or identical parts all use the same figure numbers. The implementation methods not shown or described in the drawings are forms known to those of ordinary skill in the art. In addition, although demonstrations of parameters containing specific values ​​may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint. The directional terms mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only reference to the directions of the drawings. Therefore, the phrases used are used to illustrate and are not used to limit the scope of protection of the present invention.

[0042] The vibration capacitive electrostatic sensor probe structure is composed of a first vibration plate 1, a second vibration plate 2, a sensitive plate 3, a first cantilever 4, a second cantilever 5, a bracket 6, a piezoelectric crystal 7, and a piezoelectric crystal 8. Figure 1As shown in (a), the first vibrating plate 1, the second vibrating plate 2, the first cantilever 4, the second cantilever 5 and the bracket 6 are made of the same metal material and are integrated to form a double cantilever tuning fork; the sensitive plate 3 is located below the first vibrating plate 1 and the second vibrating plate 2, and is used to sense the measured signal; the first piezoelectric crystal 7 is located on the side of the first cantilever 4, and the second piezoelectric crystal 8 is located on the side of the second cantilever 5. The first piezoelectric crystal 7 periodically expands and contracts under the action of the excitation signal, causing the tuning fork to resonate. Driven by the first cantilever 4 and the second cantilever 5, the first vibrating plate 1 and the second vibrating plate 2 move at the same speed and in opposite directions, periodically changing the exposed area of ​​the sensitive plate in the external electric field, thereby modulating the measured signal. In the non-working state, the first cantilever 4 and the second cantilever 5 of the electrostatic sensor probe are parallel, and the exposed sensitive plate area is a*l. When the first vibrating plate 1 and the second vibrating plate 2 move inward at the same time, the exposed sensitive plate area is reduced. The maximum moving distance of the first vibrating plate 1 along the central axis is Δl, and the maximum moving distance of the piezoelectric crystal 7 along the central axis is b, as shown in Figure 1 (b) When the first vibration plate 1 and the second vibration plate 2 move outward at the same time, the exposed sensitive plate area increases, and the distance between the central axes of the first vibration plate 1 and the second vibration plate 2 is l+2Δl, as shown in Figure 1 (c) as shown.

[0043] The vibration amplitude of the first piezoelectric crystal 7 under the sinusoidal excitation signal can be expressed as b·sinωt, and the vibration amplitude of the first vibrating plate 1 can be expressed as Δl·sinωt. The size of Δl depends on the position of the first cantilever 4 where the piezoelectric crystal 7 is located and the vibration mode of the tuning fork. In the two states of the area reduction of the sensitive plate 3 and the area increase of the sensitive plate 3, the area of ​​the sensitive plate 3 is a trapezoid, and its area S can be:

[0044] S=(l+2Δl·sinωt) ·a (1)

[0045] Let the vertical distance between the sensitive piece 3 and the surface of the object to be measured be d, and the capacitance formed by the two be C, then:

[0046] C=εS / d (2)

[0047] The charge accumulated by the capacitor is Q, and the induced current flowing through the sensitive chip is:

[0048] i=dQ / dt= dCV / dt= V·dC / dt+ CdV / dt (3)

[0049] Since the surface potential V of the measured object is an electrostatic potential and is much larger than the induced potential of the sensitive piece, the potential difference across the capacitor can be considered to be consistent with the surface potential of the measured object, and CdV / dt is zero. The induced current flowing through the sensitive piece is:

[0050] i=V·dC / dt=2VεΔlaω / d·cosωt. (4)

[0051] Since the maximum moving distance Δl of the vibrating plate 1 along the central axis, the height a of the sensitive plate, the angular frequency ω of the excitation signal and the vertical distance d between the sensitive plate and the surface of the measured object are known quantities, the surface potential V of the measured object can be obtained by detecting the induced current i flowing through the sensitive plate.

[0052] In order to improve the sensitivity of the electrostatic sensor, the tuning fork resonance frequency is usually set to the excitation signal frequency. However, in actual applications, due to changes in ambient temperature, the tuning fork resonance frequency is not a constant value. Figure 2 As shown, the first piezoelectric crystal 7 and the first cantilever 4 of the tuning fork are fixed with a first adhesive 9. When the ambient temperature changes, the characteristics of the first piezoelectric crystal 7 and the first adhesive 9 change accordingly, resulting in a change in the resonance frequency of the tuning fork. The piezoelectric crystal 8 is fixed to the second cantilever 5 of the tuning fork with a second adhesive 10, and the output signal of the second piezoelectric crystal 8 is used as a feedback signal to detect the tuning fork amplitude. Figure 3 As shown in the figure, when the excitation signal amplitude and frequency are fixed and the ambient temperature is set to 19°C, 24°C, and 26°C respectively, the feedback signal amplitude and phase output by the piezoelectric crystal 8 change, that is, the resonance frequency and vibration mode of the tuning fork change, which in turn causes the sensitivity of the electrostatic sensor to change, resulting in an increase in the deviation of the measurement result. Figure 4 As shown, when the surface potential of the object being measured and the sensing distance of the electrostatic sensor remain unchanged, the output reading of the electrostatic sensor generally decreases linearly with the increase of the ambient temperature, resulting in a deviation between the measurement result and the surface potential of the object being measured.

[0053] Embodiment 1: The present invention provides a compensation method for a vibrating capacitive electrostatic sensor, which is a temperature compensation method for an electrostatic sensor based on pre-calibrated parameters, such as Figure 5 As shown, including:

[0054] The temperature sensor 14 is used to detect the current ambient temperature T of the electrostatic sensor;

[0055] The microcontroller 15 controls the digital-to-analog conversion circuit 13 to generate a sinusoidal signal of a reference resonance frequency f0, and the high-frequency component and the DC component in the sinusoidal signal are eliminated by the first bandpass filter 12, and an excitation signal is formed after passing through the high-voltage amplifier circuit 11, which is loaded to the first piezoelectric crystal 7, thereby driving the tuning fork to vibrate periodically;

[0056] After the signal of the sensitive chip 3 is amplified and filtered by the preamplifier 16 and the secondary amplifier circuit 17, the first analog-to-digital conversion circuit 18 converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller 15;

[0057] The microcontroller 15 divides the collected signal amplitude by the total gain of the preamplifier 16 and the secondary amplifier circuit 17 to obtain a value V T As the input value, the output value V is obtained through the linear temperature compensation function. out , as the measurement result of the surface potential of the object being measured.

[0058] Preferably, the reference resonance frequency f0 is the resonance frequency of the tuning fork when it is at an ambient temperature T0, and T0 is a reference temperature for calibrating the output value of the electrostatic sensor.

[0059] Preferably, the linear temperature compensation function is V out =V T / K T (T-T0), K T The value range is -0.0026±0.0004.

[0060] The linear temperature compensation function has a low computational complexity and is easy to integrate into embedded devices such as handheld electrometers. However, as the working time of the electrostatic sensor increases, the vibration characteristics of the tuning fork deviate from the initial value to a certain extent, and the pre-calibrated parameters cannot fully meet the temperature characteristics of the aging tuning fork, resulting in the electrostatic sensor output reading still changing with temperature even after the above-mentioned electrostatic sensor temperature compensation method based on pre-calibrated parameters. This requires frequent calibration of the electrostatic sensor.

[0061] Embodiment 2: The present invention provides a compensation method for a vibrating capacitive electrostatic sensor, which is a temperature compensation method for an electrostatic sensor based on active search of the tuning fork resonance frequency, such as Figure 6 As shown, including:

[0062] The temperature sensor 14 is used to detect the current ambient temperature T of the electrostatic sensor;

[0063] The microcontroller 15 controls the digital-to-analog conversion circuit 13 to generate a sinusoidal signal of a reference resonance frequency f0, and the high-frequency component and the DC component in the sinusoidal signal are eliminated by the first bandpass filter 12, and the excitation signal is formed after passing through the high-voltage amplifier circuit 11 and loaded to the first piezoelectric crystal 7;

[0064] The feedback signal of the second piezoelectric crystal 8 passes through the second bandpass filter 19 to remove the high-frequency component and the low-frequency component in the feedback signal, and passes through the peak detection circuit 20. The second analog-to-digital conversion circuit 21 collects the output peak value of the peak detection circuit 20 and transmits it to the microcontroller 15.

[0065] If the output peak value deviates from the set amplitude, the microcontroller 15 gradually increases or decreases the excitation signal frequency within the set frequency range. If the acquisition peak value exceeds the set amplitude or reaches the upper and lower limits of the set frequency range, the microcontroller 15 decreases or increases the excitation signal frequency until the acquisition peak value returns to the set amplitude.

[0066] After the signal of the sensitive chip 3 is amplified and filtered by the preamplifier 16 and the secondary amplifier circuit 17, the first analog-to-digital conversion circuit 18 converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller 15;

[0067] The microcontroller 15 divides the collected signal amplitude by the total gain of the preamplifier 16 and the secondary amplifier circuit 17 to obtain a value V T As the measurement result of the surface potential of the object being measured.

[0068] Preferably, the first piezoelectric crystal 7 and the second piezoelectric crystal 8 are piezoelectric crystals of the same size and type, and the first piezoelectric crystal 7 and the second piezoelectric crystal 8 are located at the same position of their respective cantilevers.

[0069] Preferably, the reference resonance frequency f0 is the resonance frequency of the tuning fork when it is at an ambient temperature T.

[0070] Preferably, the frequency variation range of the excitation signal is limited to f0±0.1f0 to prevent the tuning fork from operating in an abnormal vibration mode.

[0071] By loading an excitation signal of the resonance frequency of the tuning fork at the ambient temperature T onto the first piezoelectric crystal 7 to drive the tuning fork to vibrate, adding a second piezoelectric crystal 8 to the other cantilever of the tuning fork to detect the vibration amplitude of the tuning fork, actively adjusting the frequency of the excitation signal within the range of the reference resonance frequency f0±0.1f0, searching for the resonance frequency of the tuning fork at the current ambient temperature, thereby ensuring that the tuning fork is always in a resonant state, avoiding changes in the vibration amplitude of the tuning fork due to changes in the ambient temperature, and improving the insensitivity of the electrostatic sensor to the ambient temperature.

[0072] From formula (4), we know that the induced current i flowing through the sensitive sheet 3 is inversely proportional to the vertical distance d between the sensitive sheet 3 and the surface of the measured object, that is, the sensing distance. When the sensing distance d changes, the induced current i changes accordingly, and it is impossible to measure the surface electrostatic potential of the measured object in a non-static state. Figure 7 As shown, when the surface potential of the object being measured and the ambient temperature of the electrostatic sensor remain unchanged, the output reading of the electrostatic sensor generally increases linearly with the increase of the reciprocal of the sensing distance, resulting in a deviation between the measurement result and the surface potential of the object being measured.

[0073] Embodiment 3: The present invention provides a compensation method for a vibration capacitive electrostatic sensor, which is a sensing distance compensation method applicable to a vibration capacitive electrostatic sensor, such as Figure 8 As shown, including:

[0074] The laser distance measuring sensor 19 is used to detect the vertical distance d between the current electrostatic sensor and the surface of the object being measured;

[0075] The microcontroller 15 controls the digital-to-analog conversion circuit 13 to generate a sinusoidal signal of a reference resonance frequency f0, and the high-frequency component and the DC component in the sinusoidal signal are eliminated by the first bandpass filter 12, and the excitation signal is formed after passing through the high-voltage amplifier circuit 11 and loaded to the first piezoelectric crystal 7;

[0076] After the signal of the sensitive chip 3 is amplified and filtered by the preamplifier 16 and the secondary amplifier circuit 17, the analog-to-digital conversion circuit 18 converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller 15;

[0077] The microcontroller 15 divides the collected signal amplitude by the total gain of the preamplifier 16 and the secondary amplifier circuit 17 to obtain a value V D As the input value, the output value V is obtained through the linear sensing distance compensation function. out , as the measurement result of the surface potential of the object being measured.

[0078] The probe of the laser distance sensor 22 and the sensitive sheet 3 are in the same plane. Preferably, the linear sensing distance compensation function is V out =V D / (K a / d+K c ), where K a The value range is 0.0144±0.0006, K c The value range is 0.4060±0.0005.

[0079] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present invention are indicated by the claims of the present application.

[0080] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A compensation method for a vibrating capacitive electrostatic sensor, characterized in that: Temperature compensation of the electrostatic sensor based on pre-calibrated parameters includes the following steps: Step S101, using a temperature sensor to detect the current ambient temperature T of the electrostatic sensor; Step S102, the microcontroller controls the digital-to-analog conversion circuit to generate a sinusoidal signal of a reference resonance frequency f0, eliminates the high-frequency component and the DC component in the sinusoidal signal through a first bandpass filter, and forms an excitation signal through a high-voltage amplifier circuit, which is loaded into the first piezoelectric crystal to drive the tuning fork to vibrate periodically; Step S103, after the signal of the sensitive chip is amplified and filtered by the preamplifier and the secondary amplifier circuit, the first analog-to-digital conversion circuit converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller; Step S104: the microcontroller divides the collected signal amplitude by the total gain of the preamplifier and the secondary amplifier circuit to obtain the value V T As the input value, the output value V is obtained through the linear temperature compensation function. out , as the measurement result of the surface potential of the object being measured.

2. A compensation method for a vibration capacitive electrostatic sensor according to claim 1, characterized in that: The reference resonance frequency f0 is the resonance frequency of the tuning fork when it is at an ambient temperature T0, and T0 is a reference temperature at which the output value of the electrostatic sensor has been calibrated.

3. The compensation method of a vibration capacitive electrostatic sensor according to claim 1, characterized in that: The linear temperature compensation function is V out =V T / K T (T-T0), where K T The value range is -0.0026±0.0004.

4. A compensation method for a vibrating capacitive electrostatic sensor, characterized in that: Temperature compensation of the electrostatic sensor based on active search of the tuning fork resonance frequency includes the following steps: Step S201, using a temperature sensor to detect the current ambient temperature T of the electrostatic sensor; Step S202, the microcontroller controls the digital-to-analog conversion circuit to generate a sinusoidal signal of a reference resonance frequency f0, eliminates the high-frequency component and the DC component in the sinusoidal signal through a first bandpass filter, and forms an excitation signal through a high-voltage amplifier circuit, which is loaded to the first piezoelectric crystal; Step S203, after the feedback signal of the second piezoelectric crystal passes through a bandpass filter, the high-frequency component and the low-frequency component in the feedback signal are removed, and after passing through a peak detection circuit, the output peak value of the peak detection circuit is collected by a second analog-to-digital conversion circuit and transmitted to a microcontroller; Step S204, if the output peak value deviates from the set amplitude, then within the set frequency range, the microcontroller gradually increases or decreases the excitation signal frequency; if the output peak value exceeds the set amplitude or reaches the upper and lower limits of the set frequency range, the microcontroller decreases or increases the excitation signal frequency until the output peak value returns to the set amplitude; Step S205, after the signal of the sensitive chip is amplified and filtered by the preamplifier and the secondary amplifier circuit, the first analog-to-digital conversion circuit converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller; Step S206: The microcontroller divides the collected signal amplitude by the total gain of the preamplifier and the secondary amplifier circuit to obtain the value V T As the measurement result of the surface potential of the object being measured.

5. A compensation method for a vibration capacitive electrostatic sensor according to claim 4, characterized in that: The first piezoelectric crystal and the second piezoelectric crystal are piezoelectric crystals of the same size and type, and the first piezoelectric crystal and the second piezoelectric crystal are located at the same position of their respective cantilevers.

6. A compensation method for a vibration capacitive electrostatic sensor according to claim 4, characterized in that: The reference resonance frequency f0 is the resonance frequency of the tuning fork when it is at an ambient temperature T.

7. A compensation method for a vibration capacitive electrostatic sensor according to claim 4, characterized in that: The frequency variation range of the excitation signal is limited to f0±0.1f0.

8. A compensation method for a vibrating capacitive electrostatic sensor, characterized in that: The sensing distance compensation of the electrostatic sensor includes the following steps: Step S301, using a laser distance measuring sensor to detect a vertical distance d between the current electrostatic sensor and the surface of the object being measured; Step S302, the microcontroller controls the digital-to-analog conversion circuit to generate a sinusoidal signal of a reference resonance frequency f0, eliminates the high-frequency component and the DC component in the sinusoidal signal through a first bandpass filter, and forms an excitation signal through a high-voltage amplifier circuit, which is loaded to the first piezoelectric crystal; Step S303, after the signal of the sensitive chip is amplified and filtered by the preamplifier and the secondary amplifier circuit, the first analog-to-digital conversion circuit converts the amplified and filtered analog signal into a digital signal and transmits it to the microcontroller; Step S304: the microcontroller divides the collected signal amplitude by the total gain of the preamplifier and the secondary amplifier circuit to obtain the value V D As the input value, the output value V is obtained through the linear sensing distance compensation function. out , as the measurement result of the surface potential of the object being measured.

9. A compensation method for a vibration capacitive electrostatic sensor according to claim 8, characterized in that: The linear sensing distance compensation function is V out =V D / (K a / d+K c ), where K a The value range of K is 0.0144±0.0006, c The value range is 0.4060±0.0005.

Images