CN101441236A - Capacity sensor circuit based on Wien bridge and phase-locked loop - Google Patents
Capacity sensor circuit based on Wien bridge and phase-locked loop Download PDFInfo
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- CN101441236A CN101441236A CNA200810207551XA CN200810207551A CN101441236A CN 101441236 A CN101441236 A CN 101441236A CN A200810207551X A CNA200810207551X A CN A200810207551XA CN 200810207551 A CN200810207551 A CN 200810207551A CN 101441236 A CN101441236 A CN 101441236A
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Abstract
A capacitor sensor circuit based on Wien bridge and phase-locked loop comprises a Wien bridge circuit, a phase-locked loop circuit and an analog-to-digital conversion circuit; wherein, one or two capacitors in the negative feedback loop of the Wien bridge circuit are sensor capacitors; the output end of the Wien bridge circuit is connected with the input end of the phase-locked loop circuit, and a frequency regulating resistance in the phase-locked loop circuit is a sensitivity condition resistance; the analog-to-digital conversion circuit is connected with the output end of the phase-locked loop circuit, which is used for conducting analog-to-digital conversion on the signal output by the phase-locked loop circuit. Furthermore, the circuit comprises an amplifying circuit connected between the output end of the phase-locked loop circuit and the analog-to-digital conversion circuit. The circuit effectively reduces noise disturbance and greatly improve measurement precision and sensitivity through effective circuit structure and modulation and demodulation process, which can be used for measuring capacitance variation with 10<-2>pF of order of magnitude.
Description
Technical field
The invention belongs to signalling arrangement and detection range, the circuit of particularly a kind ofly be applicable to fast, low noise being measured the capacitive-based sensing system.
Background technology
Current capacity measurement technology is varied, comprises height LCR tester accurately, high-precision single step electric capacity digital conversion integrated circuit, experiment instrument of low precision or the like.Different capacity measurement technology based on technology also different, therefore also have corresponding defective.For height LCR tester accurately, though the precision height, it is bulky, and price is extremely expensive, mainly satisfies breadboard accuracy requirement.The precision height of high-precision single step electric capacity digital conversion integrated circuit, price is low, good stability, but its processing speed is slow relatively.And common experiment instrument, price is low, but precision is low excessively, and speed is slow.These shortcomings have caused these test macros can't detect some sensors based on capacitance technology.And the detection system of this type of sensor needs fast, miniaturization, low noise, accurate cheaply testing capacitor value and changes in capacitance.
Summary of the invention
The object of the present invention is to provide the capacity sensor circuit based on Wien bridge circuit and phaselocked loop of a kind of high speed, small-sized, low noise.
The present invention is substituted one or two electric capacity in the feedback loop in the Wien bridge circuit by sensor capacitance, thereby variable capacitance transducer is integrated in the Wien bridge circuit, realizes the modulated process that electric bridge changes sensor capacitance.By utilizing the control of the resistance in the electric bridge negative-feedback circuit, thus easy adjusting and the optimization of finishing the working sensor frequency; The output of Wien bridge circuit is carried out demodulation by phaselocked loop, and the frequency adjustment resistance of phase-locked loop circuit self is transformed into sensitivity condition resistance here, effectively the susceptibility of setting sensor and work tolerance.The second-order low-pass filter attribute that utilizes phaselocked loop self to have is simultaneously reasonably regulated the low pass attribute, filters the voltage of exporting after the demodulation.The output voltage of phaselocked loop is through an amplifying circuit, and the reference voltage by the regulation meter circuit reaches the purpose of regulating whole sensor offset operation voltage, also reaches reduction output impedance simultaneously, adjusts circuit gain, improves the output anti-interference.
The following technical scheme of the concrete employing of the present invention:
A kind of capacity sensor circuit based on Wien bridge circuit and phaselocked loop comprises:
Wien Bridge Circuit, one or two electric capacity in the feedback loop of described Wien Bridge Circuit is sensor capacitance;
Phase-locked loop circuit, the output terminal of described Wien Bridge Circuit is connected with the input end of phase-locked loop circuit, and the frequency adjustment resistance in the described phase-locked loop circuit is sensitivity condition resistance;
Analog to digital conversion circuit is connected with the output terminal of described phase-locked loop circuit, is used for the signal of described phase-locked loop circuit output is carried out analog to digital conversion.
Further, also comprise the output terminal that is connected in described phase-locked loop circuit and the amplifying circuit between the analog to digital conversion circuit.
Further, described Wien Bridge Circuit comprises resistance R 11, resistance R 12, resistance R 13, resistance R 14, resistance R 15, resistance R 16, first amplifier element, capacitor C 11, capacitor C 12, diode D11, diode D22, described resistance R 13 is serially connected with between the electrode input end and ground of described first amplifier element, be connected between the electrode input end and output terminal of described first amplifier element after described resistance R 14 and resistance R 15 serial connections, described diode D11 forward is serially connected with between the output terminal of described resistance R 15 1 ends and first amplifier element, described diode D12 oppositely is serially connected with between the output terminal of described resistance R 15 1 ends and first amplifier element, the other end of described resistance R 15 is connected on the line between resistance R 14 and the resistance R 15, described resistance R 11 is serially connected with between the negative input and ground of described first amplifier element, described capacitor C 11 is connected in the two ends of described resistance R 11, described capacitor C 12 be connected between the negative input and output terminal of described first amplifier element after described resistance R 12 is connected in series, one or two in described capacitor C 11 and the capacitor C 12 is sensor capacitance.
Further, the model of described first amplifier element is LT1354.
Further, described phase-locked loop circuit comprises second amplifier element, the model of this second amplifier element is 74HC4046B, the output signal of described Wien Bridge Circuit is connected with the pin 14 of described second amplifier element, signal after the modulation is by pin 13 outputs of described second amplifier element, be connected with resistance R 21 between the pin R1 of described second amplifier element and the ground, be connected with resistance R 22 between the pin R2 of described second amplifier element and the ground, be connected with capacitor C 21 between the pin CIA of described second amplifier element and the pin CIB.
Further, also be connected with low-pass first order filter between described phase-locked loop circuit and the described amplifying circuit.
Further, described low-pass first order filter comprises the resistance R 23 of the output terminal that is connected in described second amplifier element and described input amplifier and is connected in capacitor C 22 between described input amplifier and the ground.
Further, described amplifying circuit comprises the 3rd amplifier element, rheostat R31, rheostat R32 and resistance R 33, the model of described the 3rd amplifier element is AD627, between described rheostat R31 and resistance R 33 serial connection back access+5V electrodes and the ground, the negative input of described the 3rd amplifier element is connected between described rheostat R31 and the resistance R 33, and described rheostat R32 is connected between the pin 1 and pin 8 of described the 3rd amplifier element.
The present invention has following beneficial effect:
1, by effective circuit structure and modulation process, effectively reduces noise jamming, improved precision and the susceptibility measured greatly, can measure 10
-2The capacitance variations of the pF order of magnitude.
2, reach error correction by the attribute resistance of adjusting circuit self, the multiplex (MUX) makes range and sets, and the purpose that bias voltage is adjusted reduces structure complexity, need not to add special-purpose functional module.
3, use the universal integrated circuit chip, cheap for manufacturing cost, the surveying instrument of same relatively precision, cost declines to a great extent.
4, advance Wien bridge circuit with capacitive transducer is integrated, electric capacity and frequency directly are coupled, and reach the purpose of modulation, and be simple in structure.
5, through simply adjusting, entire circuit can be transplanted in the detection system that obtains based on resistance variations.
Further specify the present invention below in conjunction with drawings and Examples.
Description of drawings
Fig. 1 is the capacity sensor circuit embodiment block diagram that the present invention is based on Wien bridge circuit and phaselocked loop;
Fig. 2 is the capacity sensor circuit physical circuit figure that the present invention is based on Wien bridge circuit and phaselocked loop;
Fig. 3 is Wen's bridge sensitivity distribution plan in the embodiment of the invention.
Embodiment
As shown in Figure 1, a kind of capacity sensor circuit based on Wien bridge circuit and phaselocked loop comprises:
Wien Bridge Circuit, one or two electric capacity in the feedback loop of described Wien Bridge Circuit is sensor capacitance;
Phase-locked loop circuit, the output terminal of described Wien Bridge Circuit is connected with the input end of phase-locked loop circuit, and the frequency adjustment resistance in the described phase-locked loop circuit is sensitivity condition resistance;
Amplifying circuit, the output terminal of described phase-locked loop circuit is connected with described amplifying circuit, is used for the phase-locked loop circuit output signal is amplified;
Analog to digital conversion circuit is connected with described amplifying circuit, is used for the signal of amplifying circuit output is carried out analog to digital conversion.
The capacitance variations that it is the sensor of 2pF that present embodiment is used for measuring a capacitance.This sensor is used for detecting the quantity of the living beings that move with 1.5m/s.Because the moisture of living beings is extremely low and distance is far away, so changes in capacitance only is 1%～2%, and promptly 20～40fF (10
-15F).
As shown in Figure 2, described Wien Bridge Circuit comprises resistance R 11, resistance R 12, resistance R 13, resistance R 14, resistance R 15, resistance R 16, first amplifier element, capacitor C 11, capacitor C 12, diode D11, diode D22, described resistance R 13 is serially connected with between the electrode input end and ground of described first amplifier element, be connected between the electrode input end and output terminal of described first amplifier element after described resistance R 14 and resistance R 15 serial connections, described diode D11 forward is serially connected with between the output terminal of described resistance R 15 1 ends and first amplifier element, described diode D12 oppositely is serially connected with between the output terminal of described resistance R 15 1 ends and first amplifier element, the other end of described resistance R 15 is connected on the line between resistance R 14 and the resistance R 15, described resistance R 11 is serially connected with between the negative input and ground of described first amplifier element, described capacitor C 11 is connected in the two ends of described resistance R 11, described capacitor C 12 be connected between the negative input and output terminal of described first amplifier element after described resistance R 12 is connected in series, one or two in described capacitor C 11 and the capacitor C 12 is sensor capacitance.
Wherein, first amplifier element is selected LT1354 for use, and its driving voltage is+5V.
In the present embodiment, capacitor C 11 is a sensor capacitance, and capacitor C 12 is the fixed value patch capacitor of capacitance near 2pF.Capacitor C 11 is not reciprocity with capacitor C 12 on the test susceptibility, and according to the more sensitive electric capacity of experiment concrete decision, both can not change.When capacitance during greater than 30-50pF, capacitor C 11 and capacitor C 12 all can be used sensor capacitance, can increase the response susceptibility like this.Regulate the frequency of operation that resistance R 11 and resistance R 12 can be regulated electric bridge, optimize the working point.The selection of best operating point must obtain by experiment, and theoretical model lost efficacy substantially.Fig. 3 is the susceptibility distribution plan of sensor capacitance, can see the sensor sensing degree distribution situation between different resistance R 11 and the resistance R 12, judge that by figure resistance R 11 is about 50K Ω, resistance R 12 is about 200K Ω, again through the experiment fine setting, resistance R 11, resistance R 12 are demarcated respectively at 43K Ω and 169K Ω, and the frequency of operation of this moment is 245KHz.
If make the Wien bridge circuit can steady operation, then the gain amplifier of regenerative feedback loop should be 3.The occurrence of the electric elements in the positive feedback can obtain by the Pspice emulation of the computer software, then by concrete experiment fine setting, to obtain best concussion stability.Relevant electrical equipment parameter is:
| Electrical equipment | Parameter |
| Resistance R 11 | 43KΩ |
| Resistance R 12 | 169KΩ |
| Resistance R 13 | 1KΩ |
| Resistance R 14 | 1KΩ |
| Resistance R 15 | 6KΩ |
| Resistance R 16 | 2.4KΩ |
| Diode D11, D22 | D1N914 |
As shown in Figure 2, described phase-locked loop circuit comprises second amplifier element, this second amplifier element is the 74HC4046B of Texas Instrument, its driving voltage is+5V, the output signal of described Wien Bridge Circuit is connected with the pin 14 of described second amplifier element, signal after the modulation is by pin 13 outputs of described second amplifier element, be connected with resistance R 21 between the pin R1 of described second amplifier element and the ground, be connected with resistance R 22 between the pin R2 of described second amplifier element and the ground, be connected with capacitor C 21 between the pin CIA of described second amplifier element and the pin CIB.The high precision of test circuit will realize that promptly adjust resistance R 21, resistance R 22 and capacitor C 21, concrete value is determined by experiment by the working point of regulating phaselocked loop.
In the present embodiment, also be connected with low-pass first order filter between described phase-locked loop circuit and the described amplifying circuit, described low-pass first order filter comprises the resistance R 23 of the output terminal that is connected in described second amplifier element and described input amplifier and is connected in capacitor C 22 between described input amplifier and the ground.The single order low-pass filter circuit that resistance R 23 and capacitor C 22 are formed combines with phase-locked loop circuit, forms a second-order low-pass filter.The occurrence of resistance R 13 and capacitor C 12 can tentatively be obtained by Theoretical Calculation earlier, determines end value by actual test again.Relevant electrical equipment parameter is:
| Electrical equipment | Parameter |
| Capacitor C 21 | |
| Capacitor C | |
| 22 | 1200pF |
| Resistance R 21 | 100KΩ |
| Resistance R 22 | 33KΩ |
| Resistance R 23 | 200KΩ |
The output signal of described phase-locked loop circuit has been available voltage signal, and signal to noise ratio (S/N ratio) is not less than 5, but also may exist output impedance bigger than normal, therefore shortcomings such as direct current biasing is serious, and the signal absolute value is less than normal are for the analog to digital conversion in later stage, increase by an amplifying circuit, to eliminate these shortcomings simultaneously.This amplifying circuit comprises the 3rd amplifier element, rheostat R31, rheostat R32 and resistance R 33, the 3rd amplifier element is selected AD627 for use, its driving voltage is+5V, between described rheostat R31 and resistance R 33 serial connection back access+5V electrodes and the ground, the negative input of described second amplifier element is connected between described rheostat R31 and the resistance R 33, and described rheostat R32 is connected between the pin 1 and pin 8 of described the 3rd amplifier element.Wherein, described rheostat R31 is used to regulate dc offset voltage, and rheostat R32 is used for the regulation voltage gain.The occurrence of rheostat R31 and resistance R 33 is by specific circuit application decision.
Claims (10)
1, a kind of capacity sensor circuit based on Wien bridge circuit and phaselocked loop is characterized in that comprising: Wien Bridge Circuit, and one or two electric capacity in the feedback loop of described Wien Bridge Circuit is sensor capacitance; Phase-locked loop circuit, the output terminal of described Wien Bridge Circuit is connected with the input end of phase-locked loop circuit, and the frequency adjustment resistance in the described phase-locked loop circuit is sensitivity condition resistance; Analog to digital conversion circuit is connected with the output terminal of described phase-locked loop circuit, is used for the signal of described phase-locked loop circuit output is carried out analog to digital conversion.
2, the capacity sensor circuit based on Wien bridge circuit and phaselocked loop according to claim 1 is characterized in that: also comprise the output terminal that is connected in described phase-locked loop circuit and the amplifying circuit between the analog to digital conversion circuit.
3, capacity sensor circuit based on Wien bridge circuit and phaselocked loop according to claim 2, it is characterized in that: described Wien Bridge Circuit comprises resistance R 11, resistance R 12, resistance R 13, resistance R 14, resistance R 15, resistance R 16, first amplifier element, capacitor C 11, capacitor C 12, diode D11, diode D22, described resistance R 13 is serially connected with between the electrode input end and ground of described first amplifier element, be connected between the electrode input end and output terminal of described first amplifier element after described resistance R 14 and resistance R 15 serial connections, described diode D11 forward is serially connected with between the output terminal of described resistance R 15 1 ends and first amplifier element, described diode D12 oppositely is serially connected with between the output terminal of described resistance R 15 1 ends and first amplifier element, the other end of described resistance R 15 is connected on the line between resistance R 14 and the resistance R 15, described resistance R 11 is serially connected with between the negative input and ground of described first amplifier element, described capacitor C 11 is connected in the two ends of described resistance R 11, described capacitor C 12 be connected between the negative input and output terminal of described first amplifier element after described resistance R 12 is connected in series, one or two in described capacitor C 11 and the capacitor C 12 is sensor capacitance.
4, the capacity sensor circuit based on Wien bridge circuit and phaselocked loop according to claim 3 is characterized in that: the model of described first amplifier element is LT1354.
5, according to claim 3 or 4 described capacity sensor circuits based on Wien bridge circuit and phaselocked loop, it is characterized in that: described phase-locked loop circuit comprises second amplifier element, the model of this second amplifier element is 74HC4046B, the output signal of described Wien Bridge Circuit is connected with the pin 14 of described second amplifier element, signal after the modulation is by pin 13 outputs of described second amplifier element, be connected with resistance R 21 between the pin R1 of described second amplifier element and the ground, be connected with resistance R 22 between the pin R2 of described second amplifier element and the ground, be connected with capacitor C 21 between the pin CIA of described second amplifier element and the pin CIB.
6, the capacity sensor circuit based on Wien bridge circuit and phaselocked loop according to claim 5 is characterized in that: also be connected with low-pass first order filter between described phase-locked loop circuit and the described amplifying circuit.
7, the capacity sensor circuit based on Wien bridge circuit and phaselocked loop according to claim 6 is characterized in that: described low-pass first order filter comprises the resistance R 23 of the output terminal that is connected in described second amplifier element and described input amplifier and is connected in capacitor C 22 between described input amplifier and the ground.
8, the capacity sensor circuit based on Wien bridge circuit and phaselocked loop according to claim 7, it is characterized in that: described amplifying circuit comprises the 3rd amplifier element, rheostat R31, rheostat R32 and resistance R 33, the model of described the 3rd amplifier element is AD627, between described rheostat R31 and resistance R 33 serial connection back access+5V electrodes and the ground, the negative input of described the 3rd amplifier element is connected between described rheostat R31 and the resistance R 33, and described rheostat R32 is connected between the pin 1 and pin 8 of described the 3rd amplifier element.
9, the capacity sensor circuit based on Wien bridge circuit and phaselocked loop according to claim 8, it is characterized in that: the resistance of described resistance R 11, resistance R 12, resistance R 13, resistance R 14, resistance R 15, resistance R 16 is respectively 43K Ω, 169K Ω, 1K Ω, 1K Ω, 6K Ω, 2.4K Ω, described capacitor C 21 is 10nF, described capacitor C 22 is 1200pF, and the resistance of described resistance R 21, resistance R 22, resistance R 23 is respectively 100K Ω, 33K Ω, 200K Ω.
10, the capacity sensor circuit based on Wien bridge circuit and phaselocked loop according to claim 9 is characterized in that: the model of described diode D11 and diode D22 is D1N914.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA200810207551XA CN101441236A (en) | 2008-12-23 | 2008-12-23 | Capacity sensor circuit based on Wien bridge and phase-locked loop |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA200810207551XA CN101441236A (en) | 2008-12-23 | 2008-12-23 | Capacity sensor circuit based on Wien bridge and phase-locked loop |
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| CNA200810207551XA Pending CN101441236A (en) | 2008-12-23 | 2008-12-23 | Capacity sensor circuit based on Wien bridge and phase-locked loop |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102376258A (en) * | 2010-08-16 | 2012-03-14 | 上海天马微电子有限公司 | Electronic paper drive control circuit |
| CN103812393A (en) * | 2014-02-21 | 2014-05-21 | 南通大青节能科技有限公司 | Driving circuit for permanent-magnet synchronous motor |
| CN103869176A (en) * | 2014-03-30 | 2014-06-18 | 上海理工大学 | Capacitive transducer circuit based on Wien bridge and phase-locked loop |
| CN108507695A (en) * | 2017-02-27 | 2018-09-07 | 北京自动化控制设备研究所 | A kind of atomic air chamber temperature checking method based on locking phase amplification |
| CN112816790A (en) * | 2021-02-02 | 2021-05-18 | 北京大学 | Quantum capacitance measuring system and measuring method thereof |
-
2008
- 2008-12-23 CN CNA200810207551XA patent/CN101441236A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102376258A (en) * | 2010-08-16 | 2012-03-14 | 上海天马微电子有限公司 | Electronic paper drive control circuit |
| CN102376258B (en) * | 2010-08-16 | 2014-11-12 | 上海天马微电子有限公司 | electronic paper drive control circuit |
| CN103812393A (en) * | 2014-02-21 | 2014-05-21 | 南通大青节能科技有限公司 | Driving circuit for permanent-magnet synchronous motor |
| CN103869176A (en) * | 2014-03-30 | 2014-06-18 | 上海理工大学 | Capacitive transducer circuit based on Wien bridge and phase-locked loop |
| CN108507695A (en) * | 2017-02-27 | 2018-09-07 | 北京自动化控制设备研究所 | A kind of atomic air chamber temperature checking method based on locking phase amplification |
| CN112816790A (en) * | 2021-02-02 | 2021-05-18 | 北京大学 | Quantum capacitance measuring system and measuring method thereof |
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Open date: 20090527 |