CN104569610A - Measuring circuit of micro differential capacitor - Google Patents
Measuring circuit of micro differential capacitor Download PDFInfo
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- CN104569610A CN104569610A CN201510001129.9A CN201510001129A CN104569610A CN 104569610 A CN104569610 A CN 104569610A CN 201510001129 A CN201510001129 A CN 201510001129A CN 104569610 A CN104569610 A CN 104569610A
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- differential
- operational amplifier
- operational amplifiers
- differential capacitor
- measuring circuit
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Abstract
The invention relates to a measuring circuit for a micro differential capacitor. The measuring circuit for the micro differential capacitor is mainly and technologically characterized by comprising a sine constant current excitation source, two operational amplifiers, two feedback resistors, a precise differential operational amplifier, a multiplier and two gain adjustment resistors, wherein two public pins of a measured differential capacitor are connected to the sine constant current excitation source, the other pin of the measured differential capacitor is connected to the inverted input ends of the two operational amplifiers, and the output ends of the two operational amplifiers are connected to the inverted input ends of the two operational amplifiers through the feedback resistors respectively and connected to the two input ends of the precise differential operational amplifier through the gain adjustment resistors. A differential amplification signal output by the precise differential operational amplifier is demodulated into a direct-current signal through the multiplier. By the adoption of the measuring circuit for the micro differential capacitor, the micro differential capacitor is measured in the mode of low noise, low drift, high bandwidth and high stability, and the measuring circuit can be widely applied to the application occasions needing differential capacitor measurement for micro displacement, such as a quartz flexible accelerometer.
Description
Technical field
The invention belongs to capacitance measuring technique field, especially a kind of tiny differential capacitance metering circuit.
Background technology
At present, pulse excitation level comparison expression tiny differential capacitance detection line and sinusoidal excitation bridge type tiny differential capacitance detection line are mainly contained for tiny differential capacitance measurement.Pulse excitation level comparison expression tiny differential capacitance detection line there is larger impulse noise interference and temperature stability is poor; The output impedance of sinusoidal excitation bridge type tiny differential capacitance detection line is higher, is easily subject to the impact of distribution parameter, produces deviation effects.Above two kinds of mode measuring circuit are difficult to be applied in the occasion needing high precision, high bandwidth, low noise.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art, a kind of reasonable in design, precision is high, stability is strong tiny differential capacitance metering circuit is provided.
The present invention solves its technical matters and takes following technical scheme to realize:
A kind of tiny differential capacitance metering circuit, comprise sinusoidal constant current drive source, two operational amplifiers, two feedback resistances, precision differential operational amplifier, multiplier, two gain setting resistor, the common pin of two tested differential capacitances is received on sinusoidal constant current drive source, another pin of two tested differential capacitances is connected respectively on the reverse input end of two operational amplifiers, the output terminal of two operational amplifiers is connected to the reverse input end of two operational amplifiers respectively by feedback resistance, the output terminal of two operational amplifiers is also connected to two input ends of precision differential operational amplifier respectively by gain setting resistor, the differential amplification signal that this precision differential operational amplifier exports is demodulated into direct current signal by multiplier, this signal is linear with differential electrical capacitance among a small circle, for follow-up control or processing circuitry.
And the value of described two feedback resistances is identical.
Advantage of the present invention and good effect are:
1, the present invention utilizes the input virtual earth principle of trsanscondutance amplifier to solve the contradiction of input resistant matching, utilize single channel sinusoidal excitation to ensure that circuit low noise and reduce the difficulty of line parameter circuit value symmetric design, high frequency differential effect after utilizing constant current drive source to make difference channel access trsanscondutance amplifier is inhibited, reduce further circuit noise, thus achieve low noise, low drifting, high bandwidth, the tiny differential capacitance measurement function of high stable, the application scenario that quartz flexible accelerometer etc. needs to be measured by differential capacitance measurement micrometric displacement can be widely used in.
2, resistance to overturning of the present invention depends primarily on the relative stability of the feedback resistance of two trsanscondutance amplifiers, and this circuit depending on active device performance than other more easily realizes, and performance is more reliable.
Accompanying drawing explanation
Fig. 1 is circuit theory diagrams of the present invention;
Fig. 2 is each several part circuit output waveform figure of the present invention.
Embodiment
Below in conjunction with accompanying drawing, the embodiment of the present invention is further described:
A kind of tiny differential capacitance metering circuit, two of differential capacitance individual pin are received two be respectively designed on the trsanscondutance amplifier of Striking symmetry, apply through the sinusoidal constant current drive of filtering noise reduction at the common port of differential capacitance, eventually through precision differential operational amplifier the voltage signal linear with differential capacitance variable quantity outputted in the rear class circuit of needs and go.
As shown in Figure 1, tiny differential capacitance metering circuit comprises sinusoidal constant current drive source (1), operational amplifier (5), operational amplifier (7), feedback resistance (4), feedback resistance (6), precision differential operational amplifier (10), multiplier (11), gain setting resistor (8) and gain setting resistor (9), tested differential capacitance (2), the common pin of tested differential capacitance (3) is received on sinusoidal constant current drive source (1), tested differential capacitance (2), another pin of tested differential capacitance (3) is connected respectively to operational amplifier (5), on two reverse input ends of operational amplifier (7), operational amplifier (5), the output terminal of operational amplifier (7) is respectively by feedback resistance (4), feedback resistance (6) is connected to operational amplifier (5), the reverse input end of operational amplifier (7), feedback resistance (4), feedback resistance (6) value is equal, and needs to select resistance according to actual gain.The output terminal of operational amplifier (5), operational amplifier (7) is also connected to two input ends of precision differential operational amplifier (10) respectively by resistance (8), resistance (9), the output signal of operational amplifier (5), operational amplifier (7) carries out differential amplification by precision differential operational amplifier (10), and resistance (8) and resistance (9) provide the gain-adjusted means of two paths of differential signals.The differential amplification signal that precision differential operational amplifier (10) exports is demodulated into direct current signal by multiplier (11), and this signal is linear with differential electrical capacitance among a small circle, for follow-up control or processing circuitry.
Each several part waveform in this tiny differential capacitance metering circuit as shown in Figure 2.Wherein, V1, V2 are respectively the voltage waveform of two operational amplifier pins 5, pin 7 output terminal, and the capacitance of amplitude size same electric capacity (2), electric capacity (3) is respectively directly proportional; V3 is V1, V2 output voltage waveforms after precision differential operational amplifier (10) differential amplification; V4 is the output voltage waveforms of V3 after multiplier (11) demodulation; V5 is the voltage waveform that V4 obtains on electric capacity (12) through RC low-pass filtering, and the difference value of the same electric capacity of this DC voltage (2), electric capacity (3) is linear.
It is emphasized that; embodiment of the present invention is illustrative; instead of it is determinate; therefore the present invention includes the embodiment be not limited to described in embodiment; every other embodiments drawn by those skilled in the art's technical scheme according to the present invention, belong to the scope of protection of the invention equally.
Claims (2)
1. a tiny differential capacitance metering circuit, it is characterized in that: comprise sinusoidal constant current drive source, two operational amplifiers, two feedback resistances, precision differential operational amplifier, multiplier, two gain setting resistor, the common pin of two tested differential capacitances is received on sinusoidal constant current drive source, another pin of two tested differential capacitances is connected respectively on the reverse input end of two operational amplifiers, the output terminal of two operational amplifiers is connected to the reverse input end of two operational amplifiers respectively by feedback resistance, the output terminal of two operational amplifiers is also connected to two input ends of precision differential operational amplifier respectively by gain setting resistor, the differential amplification signal that this precision differential operational amplifier exports is demodulated into direct current signal by multiplier, this signal is linear with differential electrical capacitance among a small circle, for follow-up control or processing circuitry.
2. a kind of tiny differential capacitance metering circuit according to claim 1, is characterized in that: the value of described two feedback resistances is identical.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510001129.9A CN104569610B (en) | 2015-01-05 | 2015-01-05 | A kind of tiny differential capacitance measuring circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510001129.9A CN104569610B (en) | 2015-01-05 | 2015-01-05 | A kind of tiny differential capacitance measuring circuit |
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| Publication Number | Publication Date |
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| CN104569610A true CN104569610A (en) | 2015-04-29 |
| CN104569610B CN104569610B (en) | 2017-10-03 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201510001129.9A Active CN104569610B (en) | 2015-01-05 | 2015-01-05 | A kind of tiny differential capacitance measuring circuit |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106124865A (en) * | 2016-08-31 | 2016-11-16 | 北京汽车股份有限公司 | The measuring method of the capacitance of differential capacitance and device |
| CN108680616A (en) * | 2018-05-29 | 2018-10-19 | 湖北工业大学 | A kind of humidity sensing device and method of digitized processing |
| CN113467320A (en) * | 2021-07-21 | 2021-10-01 | 西安龙飞电气技术有限公司 | Weak signal detection algorithm based on gain compensation |
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| US3812424A (en) * | 1972-09-27 | 1974-05-21 | Ade Corp | Capacitive wire gauge |
| CN101551420A (en) * | 2009-05-08 | 2009-10-07 | 北京航空航天大学 | A weak capacitive detection circuit of MEMS device |
| CN102435859A (en) * | 2011-09-21 | 2012-05-02 | 常州大学 | Small capacitance measurement circuit based on AC (alternating current) voltage drop balance and measurement method |
| US20130141121A1 (en) * | 2010-06-08 | 2013-06-06 | Iee International Electronics & Engineering S.A | "Robust Capacitive Measurement System", |
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2015
- 2015-01-05 CN CN201510001129.9A patent/CN104569610B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US3812424A (en) * | 1972-09-27 | 1974-05-21 | Ade Corp | Capacitive wire gauge |
| CN101551420A (en) * | 2009-05-08 | 2009-10-07 | 北京航空航天大学 | A weak capacitive detection circuit of MEMS device |
| US20130141121A1 (en) * | 2010-06-08 | 2013-06-06 | Iee International Electronics & Engineering S.A | "Robust Capacitive Measurement System", |
| CN102435859A (en) * | 2011-09-21 | 2012-05-02 | 常州大学 | Small capacitance measurement circuit based on AC (alternating current) voltage drop balance and measurement method |
Non-Patent Citations (1)
| Title |
|---|
| 赵礼杰: "自制桥式差分电容测量电路", 《武汉理工大学学报》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106124865A (en) * | 2016-08-31 | 2016-11-16 | 北京汽车股份有限公司 | The measuring method of the capacitance of differential capacitance and device |
| CN108680616A (en) * | 2018-05-29 | 2018-10-19 | 湖北工业大学 | A kind of humidity sensing device and method of digitized processing |
| CN108680616B (en) * | 2018-05-29 | 2021-01-01 | 湖北工业大学 | Humidity sensing device and method for digital processing |
| CN113467320A (en) * | 2021-07-21 | 2021-10-01 | 西安龙飞电气技术有限公司 | Weak signal detection algorithm based on gain compensation |
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| CN104569610B (en) | 2017-10-03 |
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