CN107560640A - Capacitance detecting device and system - Google Patents
Capacitance detecting device and system Download PDFInfo
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- CN107560640A CN107560640A CN201710856830.8A CN201710856830A CN107560640A CN 107560640 A CN107560640 A CN 107560640A CN 201710856830 A CN201710856830 A CN 201710856830A CN 107560640 A CN107560640 A CN 107560640A
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- resistance
- electric capacity
- operational amplifier
- compensation
- ultrasonic transducer
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Abstract
The invention discloses capacitance detecting device and system, is related to capacitance detecting field；Including：Capacitive micromachined ultrasonic transducer, feedback resistance, compensation resistance, compensating electric capacity and operational amplifier；The capacitive micromachined ultrasonic transducer is used to for DC offset voltage to be converted into faint current signal；Current signal faint caused by capacitive micromachined ultrasonic transducer is converted to voltage signal by the feedback resistance；The compensation resistance ensures the input of operational amplifier two, and D.C. resistance is equal over the ground；The compensating electric capacity is used for operational amplifier and carries out lead compensation；The operational amplifier is used to be amplified the current signal of input.Circuit of the present invention is simple, can effectively suppress the problem of serious of drifting about so that measurement effect is more accurate；The defects of discharge and recharge for overcoming electric capacity in conventional charge transfer method is controlled by electronic switch network, but electronic switch can bring Charge injection effect, and the influence to measurement result can not avoid completely.
Description
Technical field
The present invention relates to capacitance detecting field, especially capacitance detecting device and system.
Background technology
With the development of MEMS technology, there is capacitive micromachined ultrasonic transducer (cMUT).Capacitance type micro mechanical surpasses
Sonic transducer has high sensitivity, bandwidth, is easily manufactured to the advantages such as big array, therefore it is widely used in pressure, wet
In the detection such as degree, acceleration, displacement, gas.Capacitive micromachined ultrasonic transducer is when receiving ul-trasonic irradiation, the electricity of itself
It is only fF levels to hold change, and much smaller than the stray capacitance in circuit, while self-oscillation and conditions of streaking make output signal by shadow
Ring, and useful signal is submerged in circuit noise, increase measurement difficulty.And the resonance frequency of capacitive micromachined ultrasonic transducer
Rate belongs to high frequency weak capacitive signal detection category all between hundreds of kHz to MHz, the accuracy of detection requirement to detecting circuit
It is very high, therefore many conventional capacitance determining methods are no longer applicable.
At present, micro- capacitance determining method has discharge and recharge detection method, method of charge transfer and across resistance amplification detection method etc..Discharge and recharge
The circuit of method is simple, and relatively low realized using CMOS technology of cost is integrated, and data reading speed is very fast, and shortcoming uses direct current for it
Power supply, the drifting problem after amplification is serious, influences measurement effect；The discharge and recharge of electric capacity is by electronic switch network in method of charge transfer
To control, but electronic switch can bring Charge injection effect, and the influence to measurement result can not avoid completely.
The content of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of capacitance detecting device and system, realizes electricity
The problem of road simply overcomes drift serious so that measurement effect is more accurate；Overcome filling for electric capacity in conventional charge transfer method
Electric discharge is controlled by electronic switch network, but electronic switch can bring Charge injection effect, and the influence to measurement result can not be complete
Full the defects of avoiding.
The purpose of the present invention is achieved through the following technical solutions：Capacitance detecting device, including：Capacitance type micro mechanical
Ultrasonic transducer, feedback resistance, compensation resistance, compensating electric capacity and operational amplifier；
The capacitive micromachined ultrasonic transducer is used to for DC offset voltage to be converted into faint current signal；
Current signal faint caused by capacitive micromachined ultrasonic transducer is converted to voltage letter by the feedback resistance
Number；
The compensation resistance ensures the input of operational amplifier two, and D.C. resistance is equal over the ground；
The compensating electric capacity is used for operational amplifier and carries out lead compensation；
The operational amplifier is used to be amplified the current signal of input.
Further, capacitance detecting device, in addition to：Connect between the in-phase input end of the operational amplifier and ground connection
It is connected to an electric capacity.
Further, the electric capacity and compensation resistor coupled in parallel.
Further, the resistance of the compensation resistance is equal with the resistance of feedback resistance.
Capacitive detection system, comprise at least：Electric capacity, capacitance detecting device and single-chip microcomputer；
The electric capacity is used for output voltage；
The capacitance detecting device is used to detect the voltage of electric capacity output and exports detection signal；
The single-chip microcomputer is used for the detection signal for receiving the detection circuit output.
Further, the electric capacity is microcomputer electric capacity.
Further, the capacitance detecting device, including：Capacitive micromachined ultrasonic transducer, feedback resistance, compensation electricity
Resistance, compensating electric capacity and operational amplifier；
The capacitive micromachined ultrasonic transducer is used to for DC offset voltage to be converted into faint current signal；
Current signal faint caused by capacitive micromachined ultrasonic transducer is converted to voltage letter by the feedback resistance
Number；
The compensation resistance ensures the input of operational amplifier two, and D.C. resistance is equal over the ground；
The compensating electric capacity is used for operational amplifier and carries out lead compensation；
The operational amplifier is used to be amplified the current signal of input.
Further, an electric capacity is connected between the in-phase input end of the operational amplifier and ground connection.
Further, the electric capacity and compensation resistor coupled in parallel.
Further, the resistance of the compensation resistance is equal with the resistance of feedback resistance.
The beneficial effects of the invention are as follows：Circuit of the present invention is simple, can effectively suppress the problem of serious of drifting about so that measurement
Effect is more accurate；The discharge and recharge for overcoming electric capacity in conventional charge transfer method is controlled by electronic switch network, but electronic cutting
The defects of pass can bring Charge injection effect, and the influence to measurement result can not avoid completely.
Brief description of the drawings
Fig. 1 is the circuit theory diagrams of capacitance detecting device one embodiment；
Fig. 2 is the system block diagram of capacitive detection system one embodiment.
Embodiment
Technical scheme is described in further detail below in conjunction with the accompanying drawings, but protection scope of the present invention is not limited to
It is as described below.
As shown in figure 1, the circuit of capacitance detecting device one embodiment, is specifically included：Capacitive micromachined ultrasonic transducing
Device cMUT, feedback resistance Rf, compensation resistance R, electric capacity C, compensating electric capacity Cf and operational amplifier U；Capacitive micromachined ultrasonic
Transducer cMUT voltage input end is connected with the voltage output end of measured capacitance, capacitive micromachined ultrasonic transducer cMUT's
Input is connected with operational amplifier U backward end；One end after feedback resistance Rf is in parallel with compensating electric capacity Cf declines with electric capacity
Common portion connection between mechanical ultrasonic transducer cMUT input and operational amplifier U backward end, feedback resistance Rf
It is connected with the other end after compensating electric capacity Cf parallel connections with operational amplifier U output end；After electric capacity C is in parallel with compensation resistance R
One end is connected with operational amplifier U end in the same direction, and the other end after electric capacity C is in parallel with compensation resistance R is grounded.
Preferably, the capacitive micromachined ultrasonic transducer cMUT detections circuit is used across resistance amplification detection method.Electric capacity
Formula micromachined ultrasonic transducer is to produce Weak current in the presence of 400kHz ultrasound involves direct current biasing, and this circuit is micro- by this
Low current is converted to detectable electricity by operational amplifier U (operational amplifier U described in the present embodiment is trans-impedance amplifier)
Pressure.Need to illustrate be micro- capacitive detection circuit schematic diagram in figure, cMUT is capacitive micromachined ultrasonic transducer
Equivalent model.
Preferably, feedback resistance Rf its played a crucial role in I-V transfer processes, feedback resistance Rf and operational amplifier U
Parallel voltage negtive backword is formed, current signal faint caused by the capacitive micromachined ultrasonic transducer cMUT is converted to
The detectable voltage signal of oscillograph.Signal output waveform during due to only having feedback resistance Rf effects is in the presence of serious from exciting
Swing and conditions of streaking, it is therefore desirable to lead compensation is carried out to it with compensating electric capacity Cf, eliminates this phenomenon.In in-phase input end and connect
Connection compensation resistance R between ground, making the inputs of operational amplifier U two, D.C. resistance is equal over the ground, avoids operational amplifier U from inputting
Bias current produces additional differential-mode input voltage between two inputs, wherein compensation resistance R resistance is equal to feedback resistance
Rf resistance, the upper electric capacity C in parallel of R are used for the clutter noise for removing resistance R introducings.
As shown in Fig. 2 capacitive detection system one embodiment, is specifically included：Electric capacity, capacitance detecting device and monolithic
Machine；The electric capacity is used for output voltage；The capacitance detecting device is used to detect the voltage of electric capacity output and exports inspection
Survey signal；The single-chip microcomputer is used for the detection signal for receiving the detection circuit output.
Preferably, the capacitance detecting device specifically includes：Capacitive micromachined ultrasonic transducer cMUT, feedback resistance
Rf, compensation resistance R, electric capacity C, compensating electric capacity Cf and operational amplifier U；Capacitive micromachined ultrasonic transducer cMUT electricity
Pressure input is connected with the voltage output end of measured capacitance, and capacitive micromachined ultrasonic transducer cMUT input and computing are put
Big device U backward end is connected；One end and capacitive micromachined ultrasonic transducer after feedback resistance Rf is in parallel with compensating electric capacity Cf
Common portion connection between cMUT input and operational amplifier U backward end, feedback resistance Rf and compensating electric capacity Cf is simultaneously
The other end after connection is connected with operational amplifier U output end；One end and operation amplifier after electric capacity C is in parallel with compensation resistance R
Device U end in the same direction is connected, and the other end after electric capacity C is in parallel with compensation resistance R is grounded.
Preferably, the capacitive micromachined ultrasonic transducer cMUT detections circuit is used across resistance amplification detection method.Electric capacity
Formula micromachined ultrasonic transducer is to produce Weak current in the presence of 400kHz ultrasound involves direct current biasing, and this circuit is micro- by this
Low current is converted to detectable electricity by operational amplifier U (operational amplifier U described in the present embodiment is trans-impedance amplifier)
Pressure.Need to illustrate be micro- capacitive detection circuit schematic diagram in figure, cMUT is capacitive micromachined ultrasonic transducer
Equivalent model.
Preferably, feedback resistance Rf its played a crucial role in I-V transfer processes, feedback resistance Rf and operational amplifier U
Parallel voltage negtive backword is formed, current signal faint caused by the capacitive micromachined ultrasonic transducer cMUT is converted to
The detectable voltage signal of oscillograph.Signal output waveform during due to only having feedback resistance Rf effects is in the presence of serious from exciting
Swing and conditions of streaking, it is therefore desirable to lead compensation is carried out to it with compensating electric capacity Cf, eliminates this phenomenon.In in-phase input end and connect
Connection compensation resistance R between ground, making the inputs of operational amplifier U two, D.C. resistance is equal over the ground, avoids operational amplifier U from inputting
Bias current produces additional differential-mode input voltage between two inputs, wherein compensation resistance R resistance is equal to feedback resistance
Rf resistance, the upper electric capacity C in parallel of R are used for the clutter noise for removing resistance R introducings.
Finally illustrate, the above embodiments are merely illustrative of the technical solutions of the present invention and it is unrestricted, although with reference to compared with
The present invention is described in detail good embodiment, it will be understood by those within the art that, can be to the skill of the present invention
Art scheme is modified or equivalent substitution, and without departing from the objective and scope of technical solution of the present invention, it all should cover at this
Among the right of invention.
Claims (10)
1. capacitance detecting device, it is characterised in that including：Capacitive micromachined ultrasonic transducer, feedback resistance, compensation resistance,
Compensating electric capacity and operational amplifier；
The capacitive micromachined ultrasonic transducer is used to for DC offset voltage to be converted into faint current signal；
Current signal faint caused by capacitive micromachined ultrasonic transducer is converted to voltage signal by the feedback resistance；
The compensation resistance ensures the input of operational amplifier two, and D.C. resistance is equal over the ground；
The compensating electric capacity is used for operational amplifier and carries out lead compensation；
The operational amplifier is used to be amplified the current signal of input.
2. capacitance detecting device according to claim 1, it is characterised in that also include：In the same of the operational amplifier
An electric capacity is connected between phase input and ground connection.
3. capacitance detecting device according to claim 2, it is characterised in that：The electric capacity and compensation resistor coupled in parallel.
4. capacitance detecting device according to claim 1, it is characterised in that：The resistance and feedback resistance of the compensation resistance
Resistance it is equal.
5. utilize the capacitive detection system described in claim 1-4 any one, it is characterised in that comprise at least：Electric capacity, electric capacity
Detection means and single-chip microcomputer；
The electric capacity is used for output voltage；
The capacitance detecting device is used to detect the voltage of electric capacity output and exports detection signal；
The single-chip microcomputer is used for the detection signal for receiving the detection circuit output.
6. capacitive detection system according to claim 5, it is characterised in that：The electric capacity is microcomputer electric capacity.
7. capacitive detection system according to claim 5, it is characterised in that the capacitance detecting device, including：Condenser type
Micromachined ultrasonic transducer, feedback resistance, compensation resistance, compensating electric capacity and operational amplifier；
The capacitive micromachined ultrasonic transducer is used to for DC offset voltage to be converted into faint current signal；
Current signal faint caused by capacitive micromachined ultrasonic transducer is converted to voltage signal by the feedback resistance；
The compensation resistance ensures the input of operational amplifier two, and D.C. resistance is equal over the ground；
The compensating electric capacity is used for operational amplifier and carries out lead compensation；
The operational amplifier is used to be amplified the current signal of input.
8. capacitive detection system according to claim 7, it is characterised in that：In the in-phase input end of the operational amplifier
An electric capacity is connected between ground connection.
9. capacitance detecting device according to claim 8, it is characterised in that：The electric capacity and compensation resistor coupled in parallel.
10. capacitance detecting device according to claim 9, it is characterised in that：The resistance of the compensation resistance and feedback electricity
The resistance of resistance is equal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710856830.8A CN107560640A (en) | 2017-09-21 | 2017-09-21 | Capacitance detecting device and system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710856830.8A CN107560640A (en) | 2017-09-21 | 2017-09-21 | Capacitance detecting device and system |
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| Publication Number | Publication Date |
|---|---|
| CN107560640A true CN107560640A (en) | 2018-01-09 |
Family
ID=60982293
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
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| CN201710856830.8A Pending CN107560640A (en) | 2017-09-21 | 2017-09-21 | Capacitance detecting device and system |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109672452A (en) * | 2019-02-25 | 2019-04-23 | 深圳瑞湖科技有限公司 | A kind of pressure sensitivity key detection differential circuit and electronic equipment |
| CN109978875A (en) * | 2019-04-03 | 2019-07-05 | 无锡立赫智能科技有限公司 | A kind of capacitor open defect recognition methods and identification device |
| CN110132320A (en) * | 2019-06-13 | 2019-08-16 | 成都祥民科技发展有限责任公司 | The method for monitoring capacitance type sensor capacitance variations |
| WO2019183922A1 (en) * | 2018-03-30 | 2019-10-03 | 深圳市为通博科技有限责任公司 | Capacitive detection circuit, touch detection apparatus, and terminal device |
| CN111817697A (en) * | 2019-04-11 | 2020-10-23 | 深圳市飞翼科技有限公司 | Capacitive touch key environment compensation circuit and method |
-
2017
- 2017-09-21 CN CN201710856830.8A patent/CN107560640A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019183922A1 (en) * | 2018-03-30 | 2019-10-03 | 深圳市为通博科技有限责任公司 | Capacitive detection circuit, touch detection apparatus, and terminal device |
| US10698550B2 (en) | 2018-03-30 | 2020-06-30 | Shenzhen Weitongbo Technology Co., Ltd. | Capacitance detection circuit, touch detection device and terminal device |
| CN109672452A (en) * | 2019-02-25 | 2019-04-23 | 深圳瑞湖科技有限公司 | A kind of pressure sensitivity key detection differential circuit and electronic equipment |
| CN109978875A (en) * | 2019-04-03 | 2019-07-05 | 无锡立赫智能科技有限公司 | A kind of capacitor open defect recognition methods and identification device |
| CN111817697A (en) * | 2019-04-11 | 2020-10-23 | 深圳市飞翼科技有限公司 | Capacitive touch key environment compensation circuit and method |
| CN110132320A (en) * | 2019-06-13 | 2019-08-16 | 成都祥民科技发展有限责任公司 | The method for monitoring capacitance type sensor capacitance variations |
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Application publication date: 20180109 |