CN102944250A - Front-end conditioning circuit for measuring high impedance weak signal - Google Patents
Front-end conditioning circuit for measuring high impedance weak signal Download PDFInfo
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- CN102944250A CN102944250A CN2012104722671A CN201210472267A CN102944250A CN 102944250 A CN102944250 A CN 102944250A CN 2012104722671 A CN2012104722671 A CN 2012104722671A CN 201210472267 A CN201210472267 A CN 201210472267A CN 102944250 A CN102944250 A CN 102944250A
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Abstract
The invention provides a front-end conditioning circuit for measuring a high impedance weak signal and belongs to the technical field of spatial measurement. The circuit comprises a signal source, a first-stage amplifying circuit, a protection circuit and a second-stage amplifying and rectifying circuit, an equivalent circuit of the signal source comprises signal source voltage VS and internal resistance RS, the first-stage amplifying circuit comprises an operational amplifier A1, a capacitor C1, a resistor R1, a resistor R4 and a resistor R5, the protection circuit comprises an operational amplifier A4, a resistor R2, a resistor R3 and a capacitor C2, and the second-stage amplifying and rectifying circuit comprises an operational amplifier A2, an operational amplifier A3, a resistor R6, a resistor R7, a diode D and a capacitor C3. The front-end conditioning circuit has the advantages of being low in noise, high in input impedance, low in output impedance and capable of reducing measurement errors and achieving measurement of the high impedance weak signal.
Description
Technical field
The present invention relates to a kind of preposition modulate circuit for the high impedance weak signal measurement, belong to the space measurement technical field.
Background technology
Along with the development of spationautics, human space exploration activity is more and more frequent, and field of detecting is also more and more wider.But in the detection of space environment and effect, because the feeble signal amplitude is very low, usually flooded by very noisy, and the measurement of high impedance feeble signal easily is subject to the dividing potential drop of measuring system input impedance and the impact of system's input bias current, the detection of feeble signal is very difficult, becomes the key problem in space measurement field.
In the actual measurement, from the feeble signal amplitude of sensor output little (at tens microvolts to the hundreds of microvolt), usually be buried in other noise signals, only under the condition of establishment noise, could increase the amplitude of feeble signal.The impedance of synchronous signal is larger, is needing just can extract useful signal through various conditionings before amplifying.Therefore, need a kind of signal conditioning circuit, be used for solving the problem that the space measurement weak signal is difficult to obtain.
Summary of the invention
In order to solve weak signal measurement problem in the space exploration, the invention provides a kind of preposition modulate circuit for the high impedance weak signal measurement, can realize the measurement of high impedance feeble signal.
The objective of the invention is to be achieved through the following technical solutions.
A kind of preposition modulate circuit for the high impedance weak signal measurement, described circuit comprise that signal source, one-level amplifying circuit, holding circuit, secondary amplify and rectification circuit; Wherein the equivalent electrical circuit of signal source comprises signal source voltage V
SWith internal resistance R
SThe one-level amplifying circuit comprises operational amplifier A 1, capacitor C 1, resistance R 1, R4, R5, holding circuit comprises operational amplifier A 4, resistance R 2, R3, capacitor C 2, and secondary amplifies and rectification circuit comprises operational amplifier A 2, A3, resistance R 6, R7, diode D, capacitor C 3;
The connected mode of described preposition modulate circuit is as follows:
Wherein, signal source one end ground connection, the other end is divided into two-way after by capacitor C 1, and one the tunnel is connected with the in-phase end of operational amplifier A 1, and another road is connected with an end of resistance R 1; The end of oppisite phase of operational amplifier A 1 is connected with the in-phase end of operational amplifier A 4, the end of oppisite phase of operational amplifier A 4 is with after output terminal is connected, and then connecting resistance R3 and capacitor C 2 are divided into two-way successively, one the tunnel is connected with the other end of resistance R 1, ground connection after another road is connected with resistance R 2;
The output terminal of operational amplifier A 1 is divided into two-way, and one the tunnel with after an end of resistance R 4 is connected, through ground connection after the resistance R 5; Be connected with the end of oppisite phase of operational amplifier A 2 behind the connecting resistance R6 of another road; The end of oppisite phase of operational amplifier A 1 is connected with the other end of resistance R 4 simultaneously;
The in-phase end ground connection of operational amplifier A 2, the power end one end ground connection of operational amplifier A 2, another termination voltage signal; One end of capacitor C 3 is connected with the end of oppisite phase that resistance R 6 is connected with operational amplifier A respectively, other end ground connection; The anodic bonding of the output terminal of operational amplifier A 2 and diode D, the negative electrode of diode D is connected with the in-phase end of operational amplifier A 3, and the end of oppisite phase of operational amplifier A 3 is connected with output terminal; Resistance R 7 one ends are connected with the end of oppisite phase of operational amplifier A 2, and the other end is connected with the negative electrode of diode D;
The working method of described preposition modulate circuit is as follows:
The voltage signal that signal source is obtained enters the in-phase end of operational amplifier A 1 after capacitor C 1, after the output terminal output of operational amplifier A 1, be divided into two-way after resistance R 4, and one the tunnel enters the backward end of operational amplifier A 1; Another road enters the in-phase end of operational amplifier A 4, after the output of the output terminal of operational amplifier A 4, pass through successively resistance R 3 and capacitor C 2 after, feed back to the in-phase end of operational amplifier A 1 through resistance R 1;
Through entering the end of oppisite phase of operational amplifier A 2 after the resistance R 6, behind the output signal process diode D, feed back to the end of oppisite phase of operational amplifier A 2 through resistance R 7 through the one-level amplifying signal; Signal after the feedback enters the in-phase end of operational amplifier A 3, after the output of the output terminal of operational amplifier A 3, carries out close-loop feedback through the end of oppisite phase of operational amplifier A 3, obtains output signal from the output terminal of operational amplifier A 3.
Beneficial effect
1. when conventional method was measured, the lower end of resistance R 1 directly was connected to the ground, and the input impedance of system depends primarily on the resistance of resistance R 1, so measuring error is larger.The present invention can address this problem well by using holding circuit.Be specially the voltage follower that in low-impedance holding circuit, uses high input impedance; the electromotive force of the anti-node of circuit medium or low resistance (in-phase end of operational amplifier A 1) is forced to draw high electromotive force approximately equal with high impedance input end (signal source output terminal); then carry out one-level by the operational amplifier A 1 in the one-level amplifying circuit and amplify, the decay of weak signal is dropped to minimum.
2. in the signal condition process, the signal internal noise also is exaggerated along with signal amplifies, and wave filter need to be set eliminate this part noise.At present, for sensor signal filtering commonly used be the RC active analog wave filter that is consisted of by single operational amplifier and resistance capacitance.Simultaneously, can only input positive pulse signal in order to guarantee follow-up A/D convertor circuit, carry out rectification for the signal demand diode that contains negative pulse.Simultaneously preposition amplifier section is because the restriction of operational amplifier bandwidth, and enlargement factor may be not, and the load capacity of pre-amplification circuit is low sometimes, therefore needs to adopt the secondary of the operational amplifier of low noise, high bandwidth to amplify and rectification circuit.The present invention is by adding the voltage follower A3 of high input impedance behind diode rectification, the input impedance that further improves preposition modulate circuit suppresses noise.
Description of drawings
Fig. 1 is the circuit diagram of the preposition modulate circuit for the high impedance weak signal measurement of the present invention.
Embodiment
Below by embodiment, the present invention is further described.
The preposition modulate circuit that is used for the high impedance weak signal measurement as shown in Figure 1, described circuit comprise that signal source, one-level amplifying circuit, holding circuit, secondary amplify and rectification circuit; Wherein the equivalent electrical circuit of signal source comprises signal source voltage V
SWith internal resistance R
SThe one-level amplifying circuit comprises operational amplifier A 1, capacitor C 1, resistance R 1, R4, R5, holding circuit comprises operational amplifier A 4, resistance R 2, R3, capacitor C 2, and secondary amplifies and rectification circuit comprises operational amplifier A 2, A3, resistance R 6, R7, diode D, capacitor C 3;
For the equivalent electrical circuit of signal source, signal source voltage V
SBe 0.1mV, internal resistance R
SBe 10M Ω, the telecommunications weak signal that described signal source can produce for the probe of detector, sensor; Capacitor C 1=1nF, C2=1 μ F, C3=10 μ F, resistance R 1=100M Ω, resistance R 2=100K Ω, resistance R 3=10K Ω, resistance R 4=100K Ω, R5=R6=1K Ω, R7=100K Ω, the voltage source size of A2 is+12V; The model of operational amplifier A 1, A2, A3, A4 is AD743, and the model of diode D is 2CP33 type silicon plastic packaging rectifier diode.
The connected mode of described preposition modulate circuit is as follows:
Wherein, signal source one end ground connection, the other end is divided into two-way after by capacitor C 1, and one the tunnel is connected with the in-phase end of operational amplifier A 1, and another road is connected with an end of resistance R 1; The end of oppisite phase of operational amplifier A 1 is connected with the in-phase end of operational amplifier A 4, the end of oppisite phase of operational amplifier A 4 is with after output terminal is connected, and then connecting resistance R3 and capacitor C 2 are divided into two-way successively, one the tunnel is connected with the other end of resistance R 1, ground connection after another road is connected with resistance R 2;
The output terminal of operational amplifier A 1 is divided into two-way, and one the tunnel with after an end of resistance R 4 is connected, through ground connection after the resistance R 5; Be connected with the end of oppisite phase of operational amplifier A 2 behind the connecting resistance R6 of another road; The end of oppisite phase of operational amplifier A 1 is connected with the other end of resistance R 4 simultaneously;
The in-phase end ground connection of operational amplifier A 2, the power end one end ground connection of operational amplifier A 2, another termination voltage signal; One end of capacitor C 3 is connected with the end of oppisite phase that resistance R 6 is connected with operational amplifier A respectively, other end ground connection; The anodic bonding of the output terminal of operational amplifier A 2 and diode D, the negative electrode of diode D is connected with the in-phase end of operational amplifier A 3, and the end of oppisite phase of operational amplifier A 3 is connected with output terminal; Resistance R 7 one ends are connected with the end of oppisite phase of operational amplifier A 2, and the other end is connected with the negative electrode of diode D.
The working method of described preposition modulate circuit is as follows:
The voltage signal that signal source is obtained enters the in-phase end of operational amplifier A 1 after capacitor C 1, after the output terminal output of operational amplifier A 1, be divided into two-way after resistance R 4, and one the tunnel enters the backward end of operational amplifier A 1; Another road enters the in-phase end of operational amplifier A 4, after the output of the output terminal of operational amplifier A 4, pass through successively resistance R 3 and capacitor C 2 after, feed back to the in-phase end of operational amplifier A 1 through resistance R 1;
Through entering the end of oppisite phase of operational amplifier A 2 after the resistance R 6, behind the output signal process diode D, feed back to the end of oppisite phase of operational amplifier A 2 through resistance R 7 through the one-level amplifying signal; Signal after the feedback enters the in-phase end of operational amplifier A 3, after the output of the output terminal of operational amplifier A 3, carries out close-loop feedback through the end of oppisite phase of operational amplifier A 3, obtains output signal from the output terminal of operational amplifier A 3.
The one-level amplifying circuit adopts the in-phase proportion computing circuit with high input impedance, low output impedance, and described in-phase proportion computing circuit comprises operational amplifier A
1, resistance R 4, R5; Described in-phase proportion computing circuit is introduced the Voltage Series negative feedback and is increased input resistance, reduces output resistance.Simultaneously, because integrated transporting discharging has the common mode input, in order to improve operational precision, should select the integrated operational amplifier A4 of high cmrr.Therefore, enlargement factor A equals:
A=1+R
4/R
5
As shown in fig. 1, work as R
4=100K Ω, R
5During=1K Ω, enlargement factor A=101 doubly.
When conventional method was measured, the lower end of resistance R 1 directly was connected to the ground, and the input impedance of system depends primarily on the resistance of resistance R 1, and the equivalent input impedance of system approximates 100M Ω.Can be drawn by above analysis, its measuring error can reach 10%.So large error is unallowed in actual applications.But by the design protection circuit, can address this problem well.
In holding circuit, introduce signal to the in-phase end of operational amplifier A 4 from the end of oppisite phase of operational amplifier A 1, operational amplifier A 4 reality are voltage follower A
GuardCold end in resistance R 1 adds protection potential V
Guard, as R2〉〉 during R3, in the certain frequency scope, protection potential V
GuardBe approximately equal to high impedance input end current potential V
In, can change by the resistance of regulating resistance R2, R3 protection potential V
GuardSize.Protection potential V
GuardBy voltage follower A
GuardProvide, rather than provided by signal source, the low-impedance end of resistance R 1 adds protection potential V
GuardAfter, its voltage drop will reduce greatly, and its electric current of flowing through also will reduce greatly.
Holding circuit need to satisfy the signal path source of resistance greater than the holding circuit impedance, and described signal path source of resistance is the flow through impedance sum of one-level amplifying circuit and holding circuit of signal, that is:
Wherein, Zs is the signal path source of resistance, and Zg is the holding circuit impedance, as R2=100K Ω, and during C2=1 μ F, Zs/Zg=1000.
During the high impedance feeble signal was measured, the selection of operational amplifier was vital, needed to consider the parameters such as high input impedance, low input bias current, low noise.This circuit is selected the utmost point low noise BiFET operational amplifier A D743 of AD company, and its input bias current maximal value is 250pA, and input impedance is up to 1010 Ω, and CMRR reaches 90dB.
In the actual measuring system, for the error that the input signal cable causes, can the high as far as possible cable of choice for use insulation resistance.In addition, add protection electromotive force V at cable shield
Guard, can greatly reduce the error that the cable Leakage Current causes.Printed circuit board (PCB) causes leakage current owing to the reasons such as pollution cause insulation resistance to descend; when the operational amplifier in-phase input end is adjacent with the power supply input point; can bring interference; therefore; to be loaded on by the protection electromotive force (by the link output of capacitor C 2 and resistance R 2) that holding circuit provides around operational amplifier A 1 input end and the signal wire; with the Leakage Current that greatly reduces on the signal path, and will absorb by protected circuit from the leakage current of power supply.
In sum, above is preferred embodiment of the present invention only, is not for limiting protection scope of the present invention.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (2)
1. preposition modulate circuit that is used for the high impedance weak signal measurement, it is characterized in that: described circuit comprises that signal source, one-level amplifying circuit, holding circuit, secondary amplify and rectification circuit; Wherein the equivalent electrical circuit of signal source comprises signal source voltage V
SWith internal resistance R
SThe one-level amplifying circuit comprises operational amplifier A 1, capacitor C 1, resistance R 1, R4, R5, holding circuit comprises operational amplifier A 4, resistance R 2, R3, capacitor C 2, and secondary amplifies and rectification circuit comprises operational amplifier A 2, A3, resistance R 6, R7, diode D, capacitor C 3;
The connected mode of described preposition modulate circuit is as follows:
Wherein, signal source one end ground connection, the other end is divided into two-way after by capacitor C 1, and one the tunnel is connected with the in-phase end of operational amplifier A 1, and another road is connected with an end of resistance R 1; The end of oppisite phase of operational amplifier A 1 is connected with the in-phase end of operational amplifier A 4, the end of oppisite phase of operational amplifier A 4 is with after output terminal is connected, and then connecting resistance R3 and capacitor C 2 are divided into two-way successively, one the tunnel is connected with the other end of resistance R 1, ground connection after another road is connected with resistance R 2;
The output terminal of operational amplifier A 1 is divided into two-way, and one the tunnel with after an end of resistance R 4 is connected, through ground connection after the resistance R 5; Be connected with the end of oppisite phase of operational amplifier A 2 behind the connecting resistance R6 of another road; The end of oppisite phase of operational amplifier A 1 is connected with the other end of resistance R 4 simultaneously;
The in-phase end ground connection of operational amplifier A 2, the power end one end ground connection of operational amplifier A 2, another termination voltage signal; One end of capacitor C 3 is connected with the end of oppisite phase that resistance R 6 is connected with operational amplifier A respectively, other end ground connection; The anodic bonding of the output terminal of operational amplifier A 2 and diode D, the negative electrode of diode D is connected with the in-phase end of operational amplifier A 3, and the end of oppisite phase of operational amplifier A 3 is connected with output terminal; Resistance R 7 one ends are connected with the end of oppisite phase of operational amplifier A 2, and the other end is connected with the negative electrode of diode D.
2. a kind of preposition modulate circuit for the high impedance weak signal measurement according to claim 1 is characterized in that: signal source voltage V
SBe 0.1mV, internal resistance R
SBe 10M Ω, capacitor C 1=1nF, C2=1 μ F, C3=10 μ F, resistance R 1=100M Ω, resistance R 2=100K Ω, resistance R 3=10K Ω, resistance R 4=100K Ω, R5=R6=1K Ω, R7=100K Ω, the voltage source size of A2 is+12V; The model of operational amplifier A 1, A2, A3, A4 is AD743, and the model of diode D is 2CP33 type silicon plastic packaging rectifier diode.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012104722671A CN102944250A (en) | 2012-11-20 | 2012-11-20 | Front-end conditioning circuit for measuring high impedance weak signal |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012104722671A CN102944250A (en) | 2012-11-20 | 2012-11-20 | Front-end conditioning circuit for measuring high impedance weak signal |
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| CN102944250A true CN102944250A (en) | 2013-02-27 |
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| CN2012104722671A Pending CN102944250A (en) | 2012-11-20 | 2012-11-20 | Front-end conditioning circuit for measuring high impedance weak signal |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105048803A (en) * | 2014-11-04 | 2015-11-11 | 长沙绿智电子科技有限公司 | DC power supply circuit for detecting weak signals |
| CN105158586A (en) * | 2015-09-11 | 2015-12-16 | 兰州空间技术物理研究所 | Active space electric field detection sensor built-in circuit |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2125244A (en) * | 1982-07-24 | 1984-02-29 | Mitsubishi Electric Corp | Absolute value amplifier |
| CN1811487A (en) * | 2006-03-08 | 2006-08-02 | 中南大学 | Preamplification and filtering circuit for precision isolated amplifier |
| JP2009224956A (en) * | 2008-03-14 | 2009-10-01 | Olympus Corp | Half-wave rectifier circuit |
| CN201854195U (en) * | 2010-10-19 | 2011-06-01 | 江西启源科技发展有限公司 | Precise rectification circuit for weak signals |
-
2012
- 2012-11-20 CN CN2012104722671A patent/CN102944250A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2125244A (en) * | 1982-07-24 | 1984-02-29 | Mitsubishi Electric Corp | Absolute value amplifier |
| CN1811487A (en) * | 2006-03-08 | 2006-08-02 | 中南大学 | Preamplification and filtering circuit for precision isolated amplifier |
| JP2009224956A (en) * | 2008-03-14 | 2009-10-01 | Olympus Corp | Half-wave rectifier circuit |
| CN201854195U (en) * | 2010-10-19 | 2011-06-01 | 江西启源科技发展有限公司 | Precise rectification circuit for weak signals |
Non-Patent Citations (2)
| Title |
|---|
| 佟为明: "微机多功能电力监视仪表", 《微处理机》 * |
| 刘青峰 等: "高阻抗微弱信号测量的保护电路设计", 《测控技术》 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105048803A (en) * | 2014-11-04 | 2015-11-11 | 长沙绿智电子科技有限公司 | DC power supply circuit for detecting weak signals |
| CN105048803B (en) * | 2014-11-04 | 2018-06-26 | 湖南绿智传感技术有限公司 | A kind of DC power supply circuit for Detection of Weak Signals |
| CN105158586A (en) * | 2015-09-11 | 2015-12-16 | 兰州空间技术物理研究所 | Active space electric field detection sensor built-in circuit |
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Application publication date: 20130227 |