CN111307026A - Charge-discharge type capacitive sensor based on diode switch - Google Patents
Charge-discharge type capacitive sensor based on diode switch Download PDFInfo
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- CN111307026A CN111307026A CN201911099116.4A CN201911099116A CN111307026A CN 111307026 A CN111307026 A CN 111307026A CN 201911099116 A CN201911099116 A CN 201911099116A CN 111307026 A CN111307026 A CN 111307026A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/45—Differential amplifiers
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Abstract
The invention discloses a charging and discharging type capacitance sensor based on a diode switch, which comprises: the circuit comprises a bipolar square wave generator, a switching circuit, a trans-impedance amplifier and a differential-single end conversion circuit; the bipolar square wave generator is used for generating bipolar square waves, the switching circuit is a diode switching circuit, and the bipolar square waves control charging and discharging of the differentially changed capacitor pair to be tested under the control of the switching circuit; the trans-impedance amplifier is used for converting the charging and discharging current into a pair of large reverse voltages; the differential-single-ended conversion circuit is used for converting a pair of equal and opposite voltages output by the trans-impedance amplifier into a single-ended voltage and outputting the single-ended voltage; under the mutual cooperation of the switch circuit, the trans-impedance amplifier and the differential-single end conversion circuit, the relative capacitance of the capacitance pair to be measured is converted into an easily-measured voltage value; the precision of capacitance difference detection is improved. The invention can obtain high sensitivity and high resolution performance, and has the advantages of relatively simple circuit structure, low power consumption and the like.
Description
Technical Field
The invention belongs to the field of high-precision capacitance detection, and particularly relates to a diode switch-based charge-discharge type capacitance sensor.
Background
The high-precision capacitive displacement sensor serving as a traditional non-contact sensor has the advantages of high sensitivity and resolution, good linearity, strong anti-interference capability and the like, and is widely applied to inertial measurement devices, such as accelerometers, gyroscopes, seismometers, gravimeters, gravity gradiometers and other precision measurement devices, and the instruments have wide application and important positions in the fields of space science, earth science and the like. At present, a bridge type capacitance displacement sensor based on a transformer is applied more, the resolution ratio of the sensor is extremely high, but the circuit structure is relatively complex, and a post-processing circuit is relatively complex, so that the design requirement of low power consumption is not favorably realized.
The capacitance sensor based on the capacitance charge-discharge principle generally adopts an analog switch device to control the charge-discharge process (such as the chinese patent CN 105652099B, CN 103888128B), needs an external control signal, has a complex structure, and is easily limited in dynamic performance by factors such as dynamic response time and on-resistance of the analog switch device.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a charge-discharge type capacitive sensor which can realize high-precision capacitance difference detection and has a relatively simple structure.
The invention provides a diode switch-based charge-discharge type capacitive sensor, which comprises: the circuit comprises a bipolar square wave generator, a switching circuit, a trans-impedance amplifier and a differential-single end conversion circuit; the bipolar square wave generator is used for generating bipolar square waves, the switching circuit is a diode switching circuit, and the bipolar square waves control charging and discharging of the differentially changed capacitor pair to be tested under the control of the switching circuit; the trans-impedance amplifier is used for converting the charging and discharging current into a pair of large reverse voltages; the differential-single-ended conversion circuit is used for converting a pair of equal and opposite voltages output by the trans-impedance amplifier into a single-ended voltage and outputting the single-ended voltage; under the mutual cooperation of the switch circuit, the trans-impedance amplifier and the differential-single end conversion circuit, the relative capacitance of the capacitance pair to be measured is converted into an easily-measured voltage value; the precision of capacitance difference detection is improved.
Still further, a bipolar square wave generator includes: the system comprises a crystal oscillator, a counter, a voltage reference source module and an analog switch; after the frequency generated by the crystal oscillator is divided by the counter, the frequency is combined with the voltage reference source module to form a bipolar square wave with adjustable frequency and amplitude in a certain range under the action of the analog switch, the frequency is determined by the crystal oscillator and the counter, and the amplitude of the bipolar voltage is determined by the reference voltage source.
The voltage reference source module can be formed by connecting a plurality of voltage reference sources in parallel, so that the noise suppression effect is achieved.
Furthermore, a diode can be selected as a switch control device to be matched with the bipolar square wave for use, so that the capacitor pair to be tested can be automatically charged and discharged without an external switch control signal. Specifically, the switching circuit includes: diode D1Diode D2Diode D3And a diode D4. Diode D1Anode of (2) and diode D2The cathode of the capacitor pair to be tested is connected with CaIs a non-common terminal, diode D1Cathode and diode D3The anode of the first path of the input end of the transimpedance amplifier is connected with the 1 st input end of the transimpedance amplifier; diode D4Anode of (2) and diode D3The cathode of the capacitor pair to be tested is connected with CbIs a non-common terminal, diode D4Cathode and diode D2Is connected with the 2 nd input end of the transimpedance amplifier.
Wherein, the diode D1、D2、D3And D4The switching diode model is adopted. Preferably, in order to improve the consistency of performance parameters such as the conducting voltage, the diode is a two-way or four-way integrated high-speed switch diode.
The bipolar square wave is used as a modulation carrier signal and is used for periodically charging and discharging the capacitor to be measured. Preferably, the square wave generator should adopt a scheme with adjustable amplitude and frequency and good stability.
The charge and discharge current is converted into a pair of voltages with large inversions by using a trans-impedance amplifier, and preferably, the trans-impedance amplifier adopts an operational amplifier with low input noise current.
Wherein the transimpedance amplifier preferably has an equivalent input current noise spectral density of about 10Hz and not more than 20fA/Hz1/2The equivalent input voltage noise spectral density is around 10Hz and not more than 20nV/Hz1/2The operational amplifier of (1).
The differential-to-single-ended conversion circuit can be selected to convert a pair of equal and reverse voltages output by the trans-impedance amplifier into single-ended voltage to be output, so that the signal-to-noise ratio of the single-ended voltage signal is increased, and the resolution level of the sensing circuit is improved.
The invention realizes that the relative capacitance of the differential capacitor pair to be detected is converted into the voltage value easy to detect, and simultaneously, the diode switch circuit is utilized to carry out charge and discharge control on the capacitor to be detected under the action of no external time sequence control circuit. The sensitivity of the invention depends only on the feedback resistance RfSquare wave period f, amplitude of square wave VpAnd VnAnd the on-voltage V of the dioded。
The invention utilizes the bipolar square wave with high amplitude stability generated by the switch type square wave generator adopting the parallel reference voltage source, adopts the two-way or four-way integrated high-speed switch diode to inhibit the influence of the difference of the conduction voltages of the bipolar square wave, and obtains the performances of high sensitivity and high resolution, and simultaneously has the advantages of relatively simple circuit structure, low power consumption and the like.
Drawings
Fig. 1 is a schematic diagram of a diode switch-based charge-discharge type capacitive sensor according to the present invention.
Fig. 2 is a schematic diagram of an embodiment of a diode switch-based charge-discharge type capacitive sensor according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention particularly relates to a differential capacitance sensor with a simple structure based on a charge-discharge principle and using a diode as a switch control device, which is suitable for the field of capacitance sensors with high precision, low power consumption and high reliability, such as inertial instruments such as a space inertial sensor and the like or geophysical measuring instruments. The diode switch-based charge-discharge type capacitive sensor provided by the invention not only can realize high-precision displacement detection, but also ensures that the circuit has the characteristics of simple structure and low power consumption.
The schematic diagram of a charge-discharge type capacitance displacement sensing circuit based on a diode switch is shown in fig. 1, and the functional units of the circuit are described as follows: 1 is a bipolar square wave generator, the high and low level amplitudes of the output square wave are in equal and opposite directions and are respectively + Vp、-Vn(ii) a 2 is a differential variable capacitance pair to be measured; 3 is a diode switch circuit; 4 is a transimpedance amplifier; and 5 is a differential to single-ended conversion circuit.
The principle of the sensing circuit is summarized as follows: capacitor C to be measuredaAnd a capacitor CbIs a pair of capacitors sensitive to a certain physical quantity (such as acceleration) and producing differential change, and when the external input physical quantity is zero, CaAnd CbEqual in size, and when the input physical quantity is not zero, the capacitance CaAnd CbThe magnitude changes differentially (one increases and the other decreases, with equal amounts of change). The capacitor C is controlled by the diode switch circuit 3 by using the bipolar square wave generated by the bipolar square wave generator 1aAnd CbAnd charging and discharging. When the square wave voltage is changed from negative to positive, the square wave is applied to the capacitor CaAnd CbCharging while diode D1And D4Conducting; when the square wave voltage changes from positive to negative, the capacitor CaAnd CbAfter discharge, the diode D is charged in reverse2And D3And conducting. The capacitor C in one square wave period is calculated by the following formulaaAnd CbChange of charge amount:
Qa＝(Vp+Vn-2Vd)×Ca，Qb＝(Vp+Vn-2Vd)×Cb。
the electric quantities entering the two transimpedance amplifiers in one square wave period are respectively as follows:
Qa0＝(Vp+Vn-2Vd)×(Ca-Cb)，Qb0＝-(Vp+Vn-2Vd)×(Ca-Cb)。
since the square wave frequency is f, the currents entering the two transimpedance amplifiers are respectively:
Ia＝Qa0×f，Ib＝Qb0×f。
the gain of the transimpedance amplifier is dependent on the feedback resistance RfAnd through the action of the differential circuit, the final output voltage is:
Vout＝2Rf×(Vp+Vn-2Vd)×(Ca-Cb)。
let Δ C ═ Ca-CbThen the sensitivity coefficient of the circuit is:
K＝Vout/ΔC＝2Rf×f×(Vp+Vn-2Vd)。
the relative change of the capacitor pair can be obtained by measuring the final voltage value of the circuit, and the sensitivity of the circuit depends on the feedback resistor RfSquare wave period f, amplitude of square wave VpAnd VnAnd the on-voltage V of the dioded. For suppressing diode conducting voltage VdInfluence on sensitivity, preferably the square wave has a chosen amplitude VpAnd VnA larger bipolar square wave. To suppress the effect of the transimpedance amplifier noise, a square wave with a higher frequency is preferably used to improve the sensitivity of the sensing circuit. In order to suppress the influence of the conduction voltage of the diode and the difference of different diodes on the sensitivity and the noise floor and improve the switching rate, preferably, the four diodes are of a two-way or four-way integrated high-speed switching diode type with low conduction voltage and good consistency. Preferably, the amplifying circuit employs an operational amplifying circuit having a low input noise current.
FIG. 2 is a schematic diagram of an implementation of the above-mentioned features, which mainly includes a bipolar square wave generating circuit 1, a capacitor Ca、CbThe device comprises a pair of capacitors to be tested 2 with differential change, a diode switch circuit 3, a trans-impedance amplifier 4 and a differential-to-single-ended conversion circuit 5.
The bipolar square wave generating circuit 1 includes: the frequency generated by the crystal oscillator 11 is divided by the counter 12, and then combined with the voltage reference source module 13 (which can be realized by connecting a plurality of voltage reference sources in parallel) to form a bipolar square wave with adjustable frequency and amplitude within a certain range under the action of the analog switch 14, wherein the frequency is determined by the crystal oscillator 11 and the counter 12, and the bipolar voltage amplitude is determined by the reference voltage source 13. The capacitance C is changed when the sensitive physical quantity of the capacitance sensor changesaAnd CbThe size of the differential change (one is increased, the other is decreased, the change amount is equal), the pair of capacitors is automatically charged and discharged under the control of the diode switch circuit 3 by using the bipolar square wave, the pair of capacitor signals are converted into charging and discharging current signals, and the charging and discharging current signals are converted into a pair of large and reverse voltage signals under the action of the trans-impedance amplifier. The differential-to-single-ended conversion circuit 5 performs a difference on the voltage signals to obtain a single-ended output voltage, thereby suppressing low-frequency noise of the transimpedance amplifier. And finally, acquiring the voltage signal in real time through a voltage acquisition system, and converting the output voltage into the input capacitance difference according to the calibrated capacitance measurement sensitivity coefficient, so that the differential capacitance sensing measurement is realized. For example, the square wave amplitude is ± 10V, the frequency is 0.625MHz, the diode is an integrated double diode BAS40 of an enzimap semiconductor (NXP), the reverse recovery time is ns magnitude, and the on-voltage is about 0.3V when the forward current is 1 mA; the transimpedance amplifier adopts an operational amplifier OP297 of an Adenon semiconductor (ADI) and has lower equivalent input voltage noise of 17nV/Hz at 1kHz1/2At 10Hz, with lower equivalent input current noise of 20fA/Hz1/2Feedback resistance RfIf 1M omega is selected, the output sensitivity theoretical value of the sensing circuit is about 25V/pF.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. A diode switch based charge-discharge capacitive sensor comprising: the circuit comprises a bipolar square wave generator (1), a switching circuit (3), a trans-impedance amplifier (4) and a differential-single-ended conversion circuit (5);
the bipolar square wave generator (1) is used for generating bipolar square waves and loading the bipolar square waves at the common end of the capacitor pair (2) to be tested;
the switch circuit (3) is a diode switch circuit, and the bipolar square wave controls the charging and discharging of the differentially changed capacitor pair (2) to be tested under the control of the switch circuit (3);
the trans-impedance amplifier (4) is used for converting the charging and discharging current into a pair of large reverse voltages;
the differential-single-ended conversion circuit (5) is used for converting a pair of equal and opposite voltages output by the trans-impedance amplifier into a single-ended voltage and outputting the single-ended voltage;
under the mutual cooperation of the switch circuit (3), the trans-impedance amplifier (4) and the differential-single end conversion circuit (5), the relative capacitance of the capacitor pair (2) to be measured is converted into an easily-measured voltage value; the precision of capacitance difference detection is improved.
2. The charge-discharge capacitive sensor according to claim 1, characterized in that the bipolar square-wave generator (1) comprises: the device comprises a crystal oscillator (11), a counter (12), a voltage reference source module (13) and an analog switch (14);
after the frequency generated by the crystal oscillator (11) is divided by the counter (12), the frequency is combined with the voltage reference source module (13) to form a bipolar square wave with adjustable frequency and amplitude within a certain range under the action of the analog switch (14), the frequency is determined by the crystal oscillator (11) and the counter (12), and the amplitude of the bipolar voltage is determined by the reference voltage source (13).
3. The charge-discharge capacitive sensor according to claim 2, characterized in that the voltage reference source module (13) is connected in parallel by a plurality of voltage reference sources to achieve a noise suppression effect.
4. A charge-discharge capacitive sensor according to any of claims 1-3, characterized in that the switching circuit (3) comprises: diode D1Diode D2Diode D3And a diode D4，
Diode D1Anode of (2) and diode D2The cathode of the capacitor is connected with C in the capacitor pair (2) to be measuredaIs a non-common terminal, diode D1Cathode and diode D3The anode of the voltage regulator is connected with the 1 st input end of the transimpedance amplifier (4);
diode D4Anode of (2) and diode D3The cathode of the capacitor is connected with C in the capacitor pair (2) to be measuredbIs a non-common terminal, diode D4Cathode and diode D2The anode of the second-path resistor is connected with the 2 nd input end of the transimpedance amplifier (4).
5. The charge-discharge capacitive sensor of claim 4 wherein the diode is selected as a switch for use with a bipolar square wave to autonomously control charge and discharge without the need for external timing control signals.
6. The charge-discharge capacitive sensor of claim 5 wherein the diode D1、D2、D3And D4The two-way or four-way integrated high-speed switch diode model with relatively good performance consistency is adopted.
7. A charge-discharge capacitance sensor according to any of claims 1-6, characterized in that the charge-discharge current is converted into a pair of largely inverted voltage signals using a transimpedance amplifier (4), the transimpedance amplifier (4) preferably being used for equivalent input current noise spectral densityAt 10Hz and not more than 20fA/Hz1/2The equivalent input voltage noise spectral density is around 10Hz and not more than 20nV/Hz1/2The operational amplifier of (1).
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112325980A (en) * | 2020-10-30 | 2021-02-05 | 中国航空工业集团公司西安航空计算技术研究所 | Self-balancing alternating current bridge capacitance type oil quantity sensor acquisition device and method |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005257539A (en) * | 2004-03-12 | 2005-09-22 | Omron Corp | Optical encoder |
| CN105281567A (en) * | 2014-07-01 | 2016-01-27 | 王帅 | Low power consumption DC-DC converter |
| CN107238382A (en) * | 2017-05-22 | 2017-10-10 | 东南大学 | A kind of silicon micro-gyroscope differential capacitance detection circuit |
| CN206563771U (en) * | 2017-03-24 | 2017-10-17 | 湖北工程学院 | Capacitance measurement circuit and device |
| CN207198708U (en) * | 2017-08-31 | 2018-04-06 | 华中科技大学 | A kind of voltage-reference with noise suppressed |
-
2019
- 2019-11-11 CN CN201911099116.4A patent/CN111307026A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005257539A (en) * | 2004-03-12 | 2005-09-22 | Omron Corp | Optical encoder |
| CN105281567A (en) * | 2014-07-01 | 2016-01-27 | 王帅 | Low power consumption DC-DC converter |
| CN206563771U (en) * | 2017-03-24 | 2017-10-17 | 湖北工程学院 | Capacitance measurement circuit and device |
| CN107238382A (en) * | 2017-05-22 | 2017-10-10 | 东南大学 | A kind of silicon micro-gyroscope differential capacitance detection circuit |
| CN207198708U (en) * | 2017-08-31 | 2018-04-06 | 华中科技大学 | A kind of voltage-reference with noise suppressed |
Non-Patent Citations (2)
| Title |
|---|
| 刘殿臣 等: "《贴片元器件应用宝典》", 30 April 2009, 国防工业出版社 * |
| 祝翔宇: "高分辨率充放电式差分电容传感器研究", 《中国优秀硕士学位论文全文数据库 信息科技辑》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112325980A (en) * | 2020-10-30 | 2021-02-05 | 中国航空工业集团公司西安航空计算技术研究所 | Self-balancing alternating current bridge capacitance type oil quantity sensor acquisition device and method |
| CN112325980B (en) * | 2020-10-30 | 2024-03-01 | 中国航空工业集团公司西安航空计算技术研究所 | Self-balancing alternating current bridge type capacitive oil mass sensor acquisition device and method |
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