CN206038757U - Little current measuring device - Google Patents
Little current measuring device Download PDFInfo
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- CN206038757U CN206038757U CN201620794634.3U CN201620794634U CN206038757U CN 206038757 U CN206038757 U CN 206038757U CN 201620794634 U CN201620794634 U CN 201620794634U CN 206038757 U CN206038757 U CN 206038757U
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Abstract
The utility model belongs to small signal detection area, concretely relates to little current measuring device. Measuring device comprises switch modulation preamplification circuit, the 1st stage amplifier circuit, the 2nd stage amplifier circuit, differential demodulation circuit, state discrimination circuit, AD converting circuit and single chip circuit. The preamplification stage is enlargied signal modulate, and the current signal that will decline simultaneously changes the minute -pressure signal into, the signal amplification stage respectively by low pass filter enlarge, zero setting circuit, switch selecting circuit, state discrimination circuit constitute, carry out sample and hold by modulation switch respectively to the voltage signal after enlargeing at last, get rid of system error, output at last and the voltage signal who is directly proportional by the micrometer electric current through the differential circuit. The utility model discloses device application switch modulation, low pass filter, fortune are put feedback, multi -stage amplifiers, difference, state discrimination circuit etc. And are constituted whole measurement system, have solved the problem of multi -stage amplifiers with the operational circuit saturation, have improved measurement system's SNR.
Description
Technical field
This utility model is related to tiny signal detection field, more particularly to a kind of micro current device.
Background technology
As the test measurement under development in science and technology, maximum conditions has become the important means of further learning to Understand Nature, this
What is often measured in a little tests is all some very weak physical quantitys, and such as weak magnetic, weak sound, the low light level, weak vibration etc., due to these
Faint signal is typically all to carry out electricity conversion by sensor, makes weak signal to be measured be converted into the signal of telecommunication.It is actual to measure
When, noise and interference cannot be avoided, and have impact on sensitivity and the accuracy of measurement.For pA level current measurements, measuring circuit without
Method Direct Acquisition current signal, needs to carry out I/U conversions.It is for the voltage signal after conversion further need to be amplified, no
Then can be disturbed by the offset voltage of operational amplifier, bias current these direct current signals.Problem is to amplify capture letter to be measured
Number while, the impurity signal such as Hz noise, noise, circuit imbalance is also simultaneously exaggerated, so after needing to design correlation
Continuous circuit is filtered, is removed.For Hz noise, by taking shielding, filtering.And these are straight for circuit imbalance etc.
The elimination of stream impurity signal, needs by filtering out these impurity direct current signals using modulation circuit, difference channel.
In order to solve minimum measurement range for 10pA, accuracy is 0.5 grade of micro current problem, and this utility model is carried
A kind of micro current device is supplied
Utility model content
The technical scheme adopted by this utility model is：
Measurement apparatus are by switch modulation pre-amplification circuit, the 1st stage amplifying circuit, the 2nd stage amplifying circuit, Difference Solution
Adjust unit, state distinguishing circuit, A/D change-over circuits and single chip circuit composition.
(1) switch modulation pre-amplification circuit is by two modulation switch K1And K2, amplifier A, feedback resistance Rf, balancing resistance
R ' is constituted；Two modulation switch K1And K2By Single-chip Controlling break-make in turn, to being input into micro-current ISIt is modulated, filters impurity
Direct current signal, Jing amplifiers A amplify the micro-pressure signal U for obtaining relation proportional to measured signal0It is sent to the 1st stage amplifying circuit defeated
Enter end.
(2) the 1st stage amplifying circuits are made up of 7 grades of low channel filters and amplifier, balancing controls, 8 tunnel selecting switch；Open
Close the signal V after the micro-pressure signal and 7 grades of amplifications for modulating pre-amplification circuit output2～V8, select to open by 8 tunnel of Single-chip Controlling
Pass closes successively, 8 grades of signal V1～V8Saturation judgement unit one is sent to respectively, is judged by saturation judging circuit one, is worked as output
When signal exceedes the range of linearity of amplifier work first, single-chip microcomputer provides selection amplifier stage signal, and series falls back 1 grade, and this
Level signal is sent to the 2nd stage amplifying circuit；For avoiding power frequency interference signals from being exaggerated for several times, all arrange before every grade of amplifying circuit low
Bandpass filter；Before zeroing circuit is arranged on the final stage of amplifying circuit, to avoid measuring circuit misalignment signal itself from being amplified for several times
Afterwards, may be beyond the range of linearity of its work.
(3) the 2nd stage amplifying circuits are made up of 4 grades of low channel filters and amplifier, 4 tunnel selecting switch；1st stage amplified
Signal K of the voltage signal of circuit output Jing after the 4 grades of amplifications of the 2nd stage1～K4, closed by 4 tunnel selecting switch of Single-chip Controlling successively
Close, 4 grades of signal K1～K4Be sent to saturation judgement unit two respectively, judged by saturation judging circuit two, when output signal first
More than amplifier work the range of linearity when, single-chip microcomputer provides selection amplifier stage signal, and series falls back 1 grade, and this grade of signal sent
Toward differential ference spiral unit；Every grade of amplification is unsuitable excessive, is defined by the saturation voltage and output signal maximum that are less than amplifier.
(4) differential ference spiral unit is made up of 2 sampling holders, differential ference spiral circuit, the circuit that takes absolute value, the 2nd stage
The voltage signal of amplifying circuit output is sent to 2 sampling holders, and single-chip microcomputer provides clock signal and controls 2 samplers holdings point
Other closed and disconnected, as a result send differential ference spiral circuit, using difference channel so that companion in pre-amplification circuit, main amplifying circuit
With impurity direct current signal be eliminated；The output of difference channel is sent to the circuit that takes absolute value, and finally exports and gives A/D conversion electricity
Road.
(5) state distinguishing circuit is made up of saturation judgement unit one and saturation judgement unit two；It is defeated that 1st stage amplified signal
Go out to saturation judgement unit one, judging circuit judges result and delivers to single-chip microcomputer；2nd stage amplified signal output and sentences to saturation
Other unit two, judging circuit judges result and delivers to single-chip microcomputer.
(6) A/D change-over circuits and single chip circuit are made up of 16 A/D change-over circuits and single chip circuit, A/D conversion electricity
Road receives the output signal of differential ference spiral circuit, and the digital signal after conversion is to single-chip microcomputer, the operation of monolithic processor control device.
The course of work is：Preposition amplification stage is modulated amplification to signal, while micro-current signal is changed into minute-pressure
Signal；Signal amplification stage is respectively by low-pass filtering amplifying circuit, zeroing circuit, switch selection circuit, state distinguishing circuit structure
Into；Sampling holding is carried out respectively to the voltage signal after amplification by modulation switch finally, systematic error is removed by difference channel,
The voltage signal being directly proportional to tested micro-current is exported finally.
Advantageous Effects of the present utility model are：With switch modulation, low-pass filtering, amplifier feedback, multistage amplification, difference
Point, state distinguishing circuit etc. constitute whole measuring system, solve the problems, such as multistage amplification and discharge circuit saturation, improve survey
The signal to noise ratio of amount system.
Description of the drawings
Accompanying drawing 1 is measuring circuit system pie graph.
Accompanying drawing 2 is weak current difference, modulation preamplifier illustraton of model.
Accompanying drawing 3 is the 1st stage amplifying circuit schematic diagram
Accompanying drawing 4 is the 2nd stage amplifying circuit and differential ference spiral unit schematic diagram
Accompanying drawing 5 is state distinguishing circuit schematic diagram
Specific embodiment
Below in conjunction with the accompanying drawings the specific embodiment of this utility model device is described further.
Detection of Weak Signals seeks to filter out interference signal from signal source, strengthens and reduces to greatest extent useful
Measured signal, improves signal to noise ratio (SNR), effectively suppresses difficult point and emphasis that noise is micro current.According to the species of noise
And feature, mainly there are 2 big sources：1) from intrinsic noise inside electronic system, the bias current, offset voltage including amplifier,
Electronic component sends out thermal noise thermogenetic, the pulsed noise that digital circuit interference is produced, the spike noise that on-off circuit is produced
Deng；2) outside electronic system, Hz noise, radio noise, atmospheric noise, mechanical noise etc..In measurement, to noise
Process it is of crucial importance, micro current it is critical only that suppression circuit impurity direct current signal and Hz noise.
The measuring method of direct current impurity signal in circuit is filtered out with difference, modulation circuit, micro-current is thoroughly eliminated and is surveyed
The interference that measuring instrument circuit itself is produced during amount.Difference, modulation refer to modulation switch by central processing unit control, to micro-
Electric current is modulated, by filtering out these impurity direct current signals using modulation circuit, difference channel, obtain with measured signal into
The micro-pressure signal of proportionate relationship.Difference, modulation circuit principle are as shown in Figure 2.
Work as K1Disconnect, K2Closure, that is, export：U01=ISRf+UI0+Ib+R′+Ib-Rf
Work as K1Closure, K2Disconnect, that is, export：U01=UI0+Ib+R′+Ib-Rf
Two formulas eliminate systematic error by subtracting each other, i.e.,：U0=U01-U02=ISRf
Understand, direct current impurity signal is eliminated, U0With ISIt is directly proportional.But U0Signal is extremely weak, U0Needs are put through layer by layer
Greatly, then carry out difference.If total amplification is K, then it is output as：U0=KISRf；Tested micro-current is：IS=U0/KRf.。
Measurement apparatus are mainly made up of 3 parts as shown in Figure 1：
1) preposition amplification stage, is modulated amplification to signal, while micro-current signal is changed into micro-pressure signal；
2) signal amplification stage, respectively by low-pass filtering amplifying circuit, zeroing circuit, switch selection circuit, condition discrimination
Circuit is constituted；
3) signal output, is made up of sampling holding, difference channel etc., the voltage signal after amplification is distinguished by modulation switch
Sampling holding is carried out, systematic error is removed by difference channel, the voltage signal being directly proportional to tested micro-current is finally exported.
1st stage amplification process is divided into 7 little level (V2～V8) complete, from top to bottom gradually amplify as shown in Figure 3；It is preposition
Amplifying circuit output micro-pressure signal when being amplified in the 1st stage, by Single-chip Controlling number of stages of amplification；The determination of series first by
Variable connector is closed successively, is judged by state distinguishing circuit, when output signal exceedes the range of linearity of amplifier work first
When, series falls back 1 grade, and is sent to the amplification of the 2nd stage.For avoiding power frequency interference signals from being exaggerated for several times, every grade of amplifying circuit is all
Low pass filter is set.Zeroing circuit is arranged on the final stage of amplifying circuit, to avoid measuring circuit misalignment signal itself by for several times
After amplification, may be beyond the range of linearity of its work.
2nd stage was divided into 4 grades of amplifications, and every grade of amplification is unsuitable excessive, to be less than saturation voltage and the output of amplifier
Signal maximum is defined, as shown in Figure 4.According to the different tenses of modulation switch, the result storage that signal amplification stage is exported
In 2 depositors, using difference channel so that pre-amplification circuit, the impurity direct current signal being accompanied by main amplifying circuit
It is eliminated.
Micro current device will be also taken in addition to circuit structure design in components and parts selection, circuit installation and technique
Certain measure.For reaching pA level micro currents, it has to be noted that below some：
1) in order to avoid interference as far as possible, should be by input terminal shading ring entirely around and by screen layer and shell, lining
Bottom and it is signally connected, protection ring is arranged on into the tow sides of printed panel.
2) passage that each bar loop of circuit all should be returned using ground as electric current, in view of the impedance on ground wire is not zero and shape
Into potential difference, the Capacitance Coupled between ground wire and holding wire can further increase noise jamming, therefore, few ground connection is set as far as possible
Distance between point or reduction earth point.
3) during PCB layout, it should be noted that various devices are put, and each chip must configure decoupling capacitor, high-power unit
Requirement on devices reduces wire length as far as possible near position of source, applies copper in the output par, c large area of power supply and amplifier.Entering
During the cabling of row line plate, get ahead ground wire and power line.
According to the utility model proposes micro current device, for 10pA electric currents, instrument accuracy grade up to 0.5 grade,
With higher accuracy and preferable measurement reproducibility, stability.
Above-described is only preferred implementation of the present utility model, and this utility model is not limited to above example.Can
To understand, those skilled in the art on the premise of without departing from spirit of the present utility model and design directly derive or associate
Oher improvements and changes, are considered as being included within protection domain of the present utility model.
Claims (1)
1. a kind of micro current device, it is characterised in that measurement apparatus were put by switch modulation pre-amplification circuit, the 1st stage
Big circuit, the 2nd stage amplifying circuit, differential ference spiral unit, state distinguishing circuit, A/D change-over circuits and single chip circuit composition；
Switch modulation pre-amplification circuit is by two modulation switch K1And K2, amplifier A, feedback resistance Rf, balancing resistance R ' composition, two
Modulation switch K1And K2By Single-chip Controlling break-make in turn, to being input into micro-current ISIt is modulated, filters impurity direct current signal, Jing
Amplifier A amplifies the micro-pressure signal U for obtaining relation proportional to measured signal0It is sent to the 1st stage input amplifier；1st rank
Section amplifying circuit is made up of 7 grades of low channel filters and amplifier, balancing controls, 8 tunnel selecting switch, and switch modulation is preposition to amplify electricity
Signal V after the micro-pressure signal of road output and 7 grades of amplifications2～V8, closed by 8 tunnel selecting switch of Single-chip Controlling successively, 8 grades of letters
Number V1～V8Saturation judgement unit one is sent to respectively, is judged by saturation judging circuit one, when output signal exceedes amplifier first
During the range of linearity of work, single-chip microcomputer provides selection amplifier stage signal, and series falls back 1 grade, and this grade of signal was sent to for the 2nd stage
Amplifying circuit；Low pass filter is all set before every grade of amplifying circuit, before zeroing circuit is arranged on the final stage of 7 grades of amplifying circuits；2nd
Stage amplifying circuit is made up of 4 grades of low channel filters and amplifier, 4 tunnel selecting switch, the voltage of the 1st stage amplifying circuit output
Signal K of the signal Jing after the 4 grades of amplifications of the 2nd stage1～K4, closed by 4 tunnel selecting switch of Single-chip Controlling successively, 4 grades of signal K1~
K4Saturation judgement unit two is sent to respectively, is judged by saturation judging circuit two, when output signal is worked more than amplifier first
The range of linearity when, single-chip microcomputer be given selection amplifier stage signal, series fall back 1 grade, and this grade of signal be sent to differential ference spiral electricity
Road；Differential ference spiral unit is made up of 2 sampling holders, differential ference spiral circuit, the circuit that takes absolute value, the 2nd stage amplifying circuit
The voltage signal of output is sent to 2 sampling holders, single-chip microcomputer be given clock signal control 2 samplers keep being respectively closed and
Disconnect, as a result send differential ference spiral circuit；The output of differential ference spiral circuit is sent to the circuit that takes absolute value, and finally exports and changes to A/D
Circuit；State distinguishing circuit is made up of saturation judgement unit one and saturation judgement unit two, and the 1st stage amplified signal output to full
With judgement unit one, judging circuit judges result and delivers to single-chip microcomputer；2nd stage amplified signal output and gives saturation judgement unit
Two, judging circuit judges result and delivers to single-chip microcomputer, A/D change-over circuits and single chip circuit by 16 A/D change-over circuits and
Single chip circuit is constituted, and A/D change-over circuits receive the output signal of differential ference spiral circuit, and the digital signal after conversion is to monolithic
Machine, the operation of monolithic processor control device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620794634.3U CN206038757U (en) | 2016-07-27 | 2016-07-27 | Little current measuring device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201620794634.3U CN206038757U (en) | 2016-07-27 | 2016-07-27 | Little current measuring device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN206038757U true CN206038757U (en) | 2017-03-22 |
Family
ID=58307935
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201620794634.3U Expired - Fee Related CN206038757U (en) | 2016-07-27 | 2016-07-27 | Little current measuring device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN206038757U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108196115A (en) * | 2018-03-07 | 2018-06-22 | 漳州市东方智能仪表有限公司 | A kind of zero point adjusting method and circuit of digital direct current pincerlike meter |
-
2016
- 2016-07-27 CN CN201620794634.3U patent/CN206038757U/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108196115A (en) * | 2018-03-07 | 2018-06-22 | 漳州市东方智能仪表有限公司 | A kind of zero point adjusting method and circuit of digital direct current pincerlike meter |
| CN108196115B (en) * | 2018-03-07 | 2024-02-23 | 漳州市东方智能仪表有限公司 | Zero point adjusting method and circuit of digital direct current clamp meter |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20170322 Termination date: 20170727 |