CN101349716A - Micro-capacitance reference measuring circuit - Google Patents
Micro-capacitance reference measuring circuit Download PDFInfo
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- CN101349716A CN101349716A CNA2008100408369A CN200810040836A CN101349716A CN 101349716 A CN101349716 A CN 101349716A CN A2008100408369 A CNA2008100408369 A CN A2008100408369A CN 200810040836 A CN200810040836 A CN 200810040836A CN 101349716 A CN101349716 A CN 101349716A
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- operational amplifier
- input end
- capacitor
- capacitance
- feedback
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Abstract
The invention discloses two micro capacitance reference measuring circuits, whose circuit structure adopts the parallel connection between a reference capacity and a measured micro capacitance, wherein the excitation voltage adopts a current-limiting resistance to charge and discharge the measured micro capacitance and the reference capacity synchronously, the charge and discharge current of the measured micro capacitance and the reference capacity are converted by an inverted operational amplifier respectively into voltage signals, the ratio of the two voltage signals can be measured to attain the capacity of the measured micro capacitance. The invention eliminates the defects of the prior micro capacitance measurement circuits, has simple and cheap circuit, can further reduce the minimum measurement range of micro capacitance measurement, and can improve measurement accuracy.
Description
Technical field
The present invention relates to the application of capacitive transducer and mimic channel, be specifically related to two kinds of micro-capacitance reference measuring circuits.
Background technology
Capacitive transducer is because characteristics such as its simple in structure, high temperature resistant, anti-interference and Noninvasives, be widely used in input such as liquid level, concentration, humidity, pressure, displacement, flow, be subjected to common concern and attention in the electric and electronic industry, the 26S Proteasome Structure and Function of capacitive transducer is also being updated and is being improved.Accurate measurement to the accurate measurement, particularly little electric capacity of electric capacity is a key of guaranteeing the capacitive transducer quality.Yet the distributed capacitance of measuring input circuit might be far longer than tested little electric capacity, and it is necessary therefore seeking a kind of little capacitance measurement circuit of high precision of not measured the input circuit distribution influence.
Present little capacitance measurement circuit extensively adopts the electric charge based on operational amplifier to charge and discharge electrical method, and can range two kinds of basic skills, a kind of metering circuit that is based on capacitive feedback, and another kind is based on the metering circuit of resistance feedback.
As shown in Figure 3, a kind of metering circuit based on capacitive feedback, E is a voltage source among Fig. 3, C
XFor by micrometer electric capacity, C
D1, C
D2For measuring loop distribution electric capacity, C
FBe feedback capacity, A is an operational amplifier, S
1, S
2, S
3Be the MOS electronic switch.Work as S
1, S
3Closure, S
2Disconnect, voltage source E is to by the micrometer capacitor C
XCharge to voltage E, feedback capacity C in this process
FVoltage is 0; Work as S
1, S
3Disconnect S
2Closure is by the micrometer capacitor C
XBe discharged to 0 over the ground, the micrometer capacitor C
XElectric charge is transferred to feedback capacity C
FOn, the amplifier output voltage is EC
F/ C
X, because the virtual earth of operational amplifier is measured the loop distribution capacitor C
D2Influence eliminated.In addition, owing to adopt voltage source to discharge and recharge, measure the loop distribution capacitor C
D1Influence also eliminated.
Metering circuit based on the resistance feedback is exactly the capacitor C among Fig. 3
FChange resistance R into
FAnd remove S
3Get final product.
The shortcoming that described little capacitance measurement circuit exists is:
(1) there is distributed capacitance in the gate pole of MOS electronic switch to leakage, source electrode, and the gate pole control signal has been introduced additional discharging and recharging by these distributed capacitance.
(2) change the variation cause the input circuit structure when on off state, the transmission path of the bias current of operational amplifier is changed, cause additional discharging and recharging.
(3) capacitance voltage can not suddenly change, and charging and discharging currents is very big, and the operational amplifier output current is limited in one's ability, makes the operational amplifier reverse input end can not remain virtual earth, promptly can not guarantee linear working state all the time.
(4) capacitance voltage can not suddenly change, and charging and discharging currents is very big, causes the voltage source fluctuation.
More than these drawbacks limit little capacitance measurement circuit precision and the minimum range that can reach.
Summary of the invention
In view of above-mentioned existing little capacitance measurement circuit existing defective on technology and function thereof, in order to eliminate these defectives, technical matters to be solved by this invention is, two kinds of micro-capacitance reference measuring circuits are provided, the minimum range of little capacitance measurement circuit is further reduced, and precision further improves.
In order to address the above problem technical scheme of the present invention is such:
(1) micro-capacitance reference measuring circuit of resistance feedback, this circuit input end connect resistance R again and measure the loop distribution capacitor C by introducing the driving voltage E of random waveform
D, be divided into two-way afterwards and insert operational amplifier A respectively
1, A
2, wherein lead up to connection by the micrometer capacitor C
xWith measurement loop distribution capacitor C
D' access operational amplifier A
1Reverse input end, the positive input ground connection of this operational amplifier, output terminal U
xAnd be connected with feedback resistance R between reverse input end
1Another road is by connecting known reference capacitor C
RInsert operational amplifier A
2Reverse input end, the positive input ground connection of this operational amplifier, output terminal U
RAnd be connected with feedback resistance R between reverse input end
2
(2) micro-capacitance reference measuring circuit of capacitive feedback, this circuit input end connect resistance R again and measure the loop distribution capacitor C by introducing the driving voltage E of random waveform
D, be divided into two-way afterwards and insert operational amplifier A respectively
1, A
2, wherein lead up to connection by the micrometer capacitor C
xWith measurement loop distribution capacitor C
D' access operational amplifier A
1Reverse input end, the positive input ground connection of this operational amplifier, output terminal U
xAnd be connected in parallel to feedback resistance R between reverse input end
1With feedback capacity C
1Another road is by connecting known reference capacitor C
RInsert operational amplifier A
2Reverse input end, the positive input ground connection of this operational amplifier, output terminal U
RAnd be connected in parallel to feedback resistance R between reverse input end
2With feedback capacity C
2
The common advantage of above-mentioned two similar micro-capacitance reference measuring circuits is:
(1) owing to the effect of current-limiting resistance R, the maximum output current that allows of charging and discharging currents less-than operation amplifier can not influence operational amplifier and voltage source operate as normal;
(2) adopt the reference measurement technology, the amplitude of driving voltage and waveform are to not influence of measurement result;
(3) distributed capacitance in input measurement loop is to not influence of measurement result;
(4) the input measurement loop does not have the MOS modulation switch, the modulation error that does not exist the switch distributed capacitance to cause;
(5) the input measurement loop structure does not change in measuring process, so the bias current of operational amplifier transmission road can not cause the error that bring through variation on the transmission road through constant;
(6) measurement result and driving voltage size and waveform are irrelevant, so driving voltage does not require very steady very accurate.
Different is because the difference of feedback element, and the stability of feedback resistance is better than the stability of feedback capacity.
Description of drawings
Describe the present invention in detail below in conjunction with the drawings and specific embodiments;
Fig. 1 is the schematic diagram of the micro-capacitance reference measuring circuit of one of circuit of the present invention resistance feedback;
Fig. 2 is the schematic diagram of the micro-capacitance reference measuring circuit of two capacitive feedback of circuit of the present invention;
Fig. 3 is the schematic diagram of a kind of metering circuit based on capacitive feedback in the background technology.
Embodiment
For technological means, creation characteristic that the present invention is realized, reach purpose and effect is easy to understand, below in conjunction with concrete diagram, further set forth the present invention.
Embodiment 1: the micro-capacitance reference measuring circuit of resistance feedback.
As shown in Figure 1, C
xFor by micrometer electric capacity, C
RBe known reference electric capacity, C
D, C
D' for measuring loop distribution electric capacity, E is the driving voltage of random waveform, R is a current-limiting resistance, A
1, A
2Be operational amplifier, R
1, R
2Be respectively feedback resistance.The reference capacitor C
ROne end with by the micrometer capacitor C
xOne end links, by the micrometer capacitor C
xThe other end is linked one group of operational amplifier A
1Inverting input, the reference capacitor C
RThe other end is linked another group operational amplifier A
2Inverting input, current-limiting resistance R one end and excitation voltage source E link, the other end and reference capacitor C
RWith by the micrometer capacitor C
xPublic union end link.Measuring method is: a point voltage is u, operational amplifier, A
1, A
2Output be respectively:
U is by the micrometer capacitor C in the formula
XVoltage, also be the reference capacitor C
RVoltage.Measured capacitance C
XFor:
As seen, by measuring operational amplifier A
1, A
2Output voltage, can record by micrometer electric capacity through calculating.
Embodiment 2: the micro-capacitance reference measuring circuit of capacitive feedback.
As shown in Figure 2, C
xFor by micrometer electric capacity, C
RBe known reference electric capacity, C
D,C
D' for measuring loop distribution electric capacity, E is the driving voltage of random waveform, R is a current-limiting resistance, A
1, A
2Be operational amplifier, C
1, C
2Be respectively feedback capacity.In order to eliminate the integral action of operational amplifier bias current to feedback capacity, resistance R that resistance is higher in parallel respectively at the feedback capacity two ends
1, R
2.a point voltage is u, ignores R
1, R
2Influence, operational amplifier A
1, A
2Output be respectively:
U
x＝C
xu/C
1 (1)
U
R＝C
Ru/C
2 (2)
U is by the micrometer capacitor C in the formula
XVoltage, also be the reference capacitor C
RVoltage.Measured capacitance C
XFor:
As seen, by measuring operational amplifier A
1, A
2Output voltage, can record by micrometer electric capacity through calculating.Through calculating, desirable 0.01 microfarad of reference electric capacity, the electric capacity of this numerical value is bigger, does not belong to little electric capacity, therefore by the simple transformation to circuit, can implement online accurate measurement to reference electric capacity, thereby guarantee by the measuring accuracy of micrometer electric capacity.
Above-mentioned two embodiment compare, and both circuit structures are basic identical, and different is because the difference of feedback element, and the stability of feedback resistance is better than the stability of feedback capacity.
More than show and described ultimate principle of the present invention, principal character and advantage of the present invention.The technician of the industry should understand; the present invention is not restricted to the described embodiments; that describes in the foregoing description and the instructions just illustrates principle of the present invention; the present invention also has various changes and modifications without departing from the spirit and scope of the present invention, and these changes and improvements all fall in the claimed scope of the invention.The claimed scope of the present invention is defined by appending claims and equivalent thereof.
Claims (2)
1, micro-capacitance reference measuring circuit is characterized in that, this circuit input end connects resistance R again and measures the loop distribution capacitor C by introducing the driving voltage E of random waveform
D, be divided into two-way afterwards and insert operational amplifier A respectively
1, A
2, wherein lead up to connection by the micrometer capacitor C
xWith measurement loop distribution capacitor C
D /Insert operational amplifier A
1Reverse input end, the positive input ground connection of this operational amplifier, output terminal U
xAnd be connected with feedback resistance R between reverse input end
1Another road is by connecting known reference capacitor C
RInsert operational amplifier A
2Reverse input end, the positive input ground connection of this operational amplifier, output terminal U
RAnd be connected with feedback resistance R between reverse input end
2
2, micro-capacitance reference measuring circuit is characterized in that, this circuit input end connects resistance R again and measures the loop distribution capacitor C by introducing the driving voltage E of random waveform
D, be divided into two-way afterwards and insert operational amplifier A respectively
1, A
2, wherein lead up to connection by the micrometer capacitor C
xWith measurement loop distribution capacitor C
D /Insert operational amplifier A
1Reverse input end, the positive input ground connection of this operational amplifier, output terminal U
xAnd be connected in parallel to feedback resistance R between reverse input end
1With feedback capacity C
1Another road is by connecting known reference capacitor C
RInsert operational amplifier A
2Reverse input end, the positive input ground connection of this operational amplifier, output terminal U
RAnd be connected in parallel to feedback resistance R between reverse input end
2With feedback capacity C
2
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008100408369A CN101349716B (en) | 2008-07-22 | 2008-07-22 | Micro-capacitance reference measuring circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008100408369A CN101349716B (en) | 2008-07-22 | 2008-07-22 | Micro-capacitance reference measuring circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101349716A true CN101349716A (en) | 2009-01-21 |
| CN101349716B CN101349716B (en) | 2012-06-20 |
Family
ID=40268576
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2008100408369A Expired - Fee Related CN101349716B (en) | 2008-07-22 | 2008-07-22 | Micro-capacitance reference measuring circuit |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102012464A (en) * | 2010-09-30 | 2011-04-13 | 彭建学 | Micro capacitance measurement method and special device |
| CN102270075A (en) * | 2011-03-25 | 2011-12-07 | 苏州瀚瑞微电子有限公司 | Capacity measurement method for capacitive touch screen scanning line and circuit module |
| CN101833042B (en) * | 2009-03-09 | 2012-07-18 | 瑞鼎科技股份有限公司 | Capacitance measuring circuit and comprehensive control circuit applying same |
| CN103269203A (en) * | 2013-06-05 | 2013-08-28 | 歌尔声学股份有限公司 | Biasing circuit of operational amplifier |
| CN103308774A (en) * | 2012-03-09 | 2013-09-18 | 帕拉贡股份公司 | Device and method used for determining measuring value of direct ratio between inductances or capacitances of two inductor or capacitor assemblies |
| CN103714330A (en) * | 2014-01-06 | 2014-04-09 | 李扬渊 | Capacitive fingerprint sensor |
| CN105974202A (en) * | 2016-06-21 | 2016-09-28 | 北京华峰测控技术有限公司 | Micro-capacitance reference measurement circuit with multiple measuring ranges and measurement method thereof |
| CN108613718A (en) * | 2016-12-12 | 2018-10-02 | 中国航空工业集团公司西安航空计算技术研究所 | The anti-interference measuring system of aviation fuel-quantity transducer overlength distance |
| CN110501575A (en) * | 2019-08-02 | 2019-11-26 | 苏州大学 | The quick micro- capacitance measurement system of superhigh precision |
| CN113075459A (en) * | 2021-03-18 | 2021-07-06 | 合肥恒钧检测技术有限公司 | Electrostatic capacity detection device |
| CN116859126A (en) * | 2023-08-31 | 2023-10-10 | 国网山东省电力公司泰安供电公司 | AC impedance spectrum measurement system and method based on double-channel half-bridge method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2056515U (en) * | 1988-01-30 | 1990-04-25 | 北京大学 | Current compensation type micro-capacitivity test device |
| DE19833211C2 (en) * | 1998-07-23 | 2000-05-31 | Siemens Ag | Method for determining very small capacities and use |
-
2008
- 2008-07-22 CN CN2008100408369A patent/CN101349716B/en not_active Expired - Fee Related
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101833042B (en) * | 2009-03-09 | 2012-07-18 | 瑞鼎科技股份有限公司 | Capacitance measuring circuit and comprehensive control circuit applying same |
| CN102012464B (en) * | 2010-09-30 | 2012-10-31 | 彭建学 | Micro capacitance measurement method and special device |
| CN102012464A (en) * | 2010-09-30 | 2011-04-13 | 彭建学 | Micro capacitance measurement method and special device |
| CN102270075A (en) * | 2011-03-25 | 2011-12-07 | 苏州瀚瑞微电子有限公司 | Capacity measurement method for capacitive touch screen scanning line and circuit module |
| CN103308774B (en) * | 2012-03-09 | 2017-09-12 | 帕拉贡股份公司 | For the apparatus and method for the measured value for determining to be directly proportional to the ratio between the inductance or electric capacity of two inductance or capacitance component |
| CN103308774A (en) * | 2012-03-09 | 2013-09-18 | 帕拉贡股份公司 | Device and method used for determining measuring value of direct ratio between inductances or capacitances of two inductor or capacitor assemblies |
| CN103269203A (en) * | 2013-06-05 | 2013-08-28 | 歌尔声学股份有限公司 | Biasing circuit of operational amplifier |
| CN103714330A (en) * | 2014-01-06 | 2014-04-09 | 李扬渊 | Capacitive fingerprint sensor |
| CN103714330B (en) * | 2014-01-06 | 2017-12-19 | 苏州迈瑞微电子有限公司 | Capacitive fingerprint sensor |
| CN105974202A (en) * | 2016-06-21 | 2016-09-28 | 北京华峰测控技术有限公司 | Micro-capacitance reference measurement circuit with multiple measuring ranges and measurement method thereof |
| CN105974202B (en) * | 2016-06-21 | 2019-06-28 | 北京华峰测控技术股份有限公司 | With multiple range micro-capacitance reference measuring circuit and method |
| CN108613718A (en) * | 2016-12-12 | 2018-10-02 | 中国航空工业集团公司西安航空计算技术研究所 | The anti-interference measuring system of aviation fuel-quantity transducer overlength distance |
| CN108613718B (en) * | 2016-12-12 | 2020-01-14 | 中国航空工业集团公司西安航空计算技术研究所 | Ultra-long distance anti-interference measuring system of aviation fuel quantity sensor |
| CN110501575A (en) * | 2019-08-02 | 2019-11-26 | 苏州大学 | The quick micro- capacitance measurement system of superhigh precision |
| CN113075459A (en) * | 2021-03-18 | 2021-07-06 | 合肥恒钧检测技术有限公司 | Electrostatic capacity detection device |
| CN113075459B (en) * | 2021-03-18 | 2023-02-03 | 合肥恒钧检测技术有限公司 | Electrostatic capacity detection device |
| CN116859126A (en) * | 2023-08-31 | 2023-10-10 | 国网山东省电力公司泰安供电公司 | AC impedance spectrum measurement system and method based on double-channel half-bridge method |
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| Publication number | Publication date |
|---|---|
| CN101349716B (en) | 2012-06-20 |
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