CN103713181B - Weak current signal supervisory instrument - Google Patents
Weak current signal supervisory instrument Download PDFInfo
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- CN103713181B CN103713181B CN201310743456.2A CN201310743456A CN103713181B CN 103713181 B CN103713181 B CN 103713181B CN 201310743456 A CN201310743456 A CN 201310743456A CN 103713181 B CN103713181 B CN 103713181B
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Abstract
The invention discloses a kind of Weak current signal supervisory instrument, comprise power frequency change-over circuit and its main operational circuit, power frequency change-over circuit comprises current integration circuit, thresholding controls and capacitor charging protection circuit, sequence circuit and constant-current source circuit; Current integration circuit comprises resistance R, operational amplifier I and electric capacity C; Thresholding controls and capacitor charging protection circuit comprises diode, resistance and triode; The CPLD of what the control chip of sequence circuit adopted is Xilinx; Constant-current source circuit comprises operational amplifier II, triode and resistance.This device has broken away from the dependence to sampling resistor, reduces the requirement to resistance, reduces installation cost, improves the stability of device simultaneously.
Description
Technical field
The present invention relates to a kind of current signal detecting device, particularly relate to a kind of Weak current signal supervisory instrument, this device is applicable to the detection of various Weak current, extensively can be suitable in fields such as medical treatment, navigation, measurements, improves the detectability of equipment.
Background technology
All can occur the detection of Weak current signal in a lot of field, detection method mostly in the past is, by sampling resistor, current signal is converted to voltage signal, is carried out converting corresponding digital signal to by voltage signal, then show or send by A/D chip; Also have and adopt V_F conversion chip, the voltage signal after being changed by sampling resistor converts frequency signal to, then converts frequency signal to current value by compute chip, shows or send.
The testing product relative merits of existing current signal:
1, traditional device current signal being converted to current value by sampling resistor and A/D chip, its advantage is: circuit is simple, easily realizes.Its shortcoming is: the degree of dependence of sampling resistor is high, requires that sampling resistor has high precision, good temperature characterisitic; The requirement of A/D chip is high, and the quality of A/D chip directly determines the precision of equipment; Device cost is high, detect Weak current signal, has higher requirement to sampling resistor and A/D chip, and resistance high-end like this and A/D chip cause the cost of whole equipment to uprise.
2, convert current signal to voltage signal by sampling resistor, by V_F conversion chip, convert the signal into corresponding frequency signal, carry out frequency counting by chip, finally convert corresponding digital signal to.Although this method reduces the requirement to chip, still do not break away from the dependence to sampling resistor.The stability of whole equipment is caused to can not get promoting.
Summary of the invention
For above shortcomings part in prior art, the invention provides a kind of Weak current signal supervisory instrument.This Weak current signal supervisory instrument makes the detection of Weak current break away from dependence to sampling resistor and chip, improves accuracy of detection and the degree of stability of equipment, reduces the cost of this series products.
In order to solve the problems of the technologies described above, present invention employs following technical scheme:
Weak current signal supervisory instrument, comprise power frequency change-over circuit and its main operational circuit, current signal input current freq converting circuit, power frequency change-over circuit is converted to frequency signal input core computing circuit, exported by current value by its main operational circuit, described power frequency change-over circuit comprises current integration circuit, thresholding controls and capacitor charging protection circuit, sequence circuit and constant-current source circuit again;
Described current integration circuit comprises resistance R, operational amplifier I and electric capacity C; Current signal is connected with one end of resistance R, and the other end of described resistance R is all connected with the negative electrode of operational amplifier I with one end of electric capacity C, the plus earth of described operational amplifier I;
Described thresholding controls and capacitor charging protection circuit comprises diode VZ, diode VF, resistance RZ1, resistance RZ2, resistance RM1, resistance RM2, resistance RF1, resistance RF2, resistance RM3, resistance RM4, triode VZT and triode VFT; The output terminal of described operational amplifier I is connected with the positive pole of diode VZ and the negative pole of diode VF respectively, the base stage of the negative pole connecting triode VZT of described diode VZ, the collector of described triode VZT is connected with+5V power supply, the emitter of described triode VZT is connected with one end of resistance RZ2, one end of described resistance RZ1 is connected with the base stage of triode VZT, and the other end of described resistance RZ1 is connected with the collector of triode VZT; The positive pole of described diode VF is connected with the base stage of triode VFT, the collector of described triode VFT is connected with-5V power supply, the emitter of described triode VFT is connected with one end of resistance RF2, one end of described resistance RF1 is connected with the base stage of triode VFT, and the other end of described resistance RF1 is connected with the collector of triode VFT; One end of described resistance RM1 is connected with the collector of triode VZT, and the other end of described resistance RM1 is connected with one end of resistance RM2, and one end of described resistance RM4 is connected with the collector of triode VFT, and the other end of resistance RM4 is connected with one end of resistance RM3; The other end of described resistance RZ2 is connected with the other end of resistance RF2, the other end of described resistance RM2 is connected with the other end of resistance RM3, and the other end and the resistance RM2 of described resistance RZ2 and resistance RF2 are connected with the other end of electric capacity C respectively with the other end of resistance RM3;
The CPLD of what the control chip of described sequence circuit adopted is Xilinx, the I/O interface of this chip is accessed in the other end of described resistance RM1 and one end of resistance RM2; The I/O interface of this chip is accessed in the other end of described resistance RM4 and one end of resistance RM3;
Described constant-current source circuit comprises operational amplifier II, triode M1, triode M2, triode M3 and resistance R1; The anode of described operational amplifier II is connected with 10V power supply, the output terminal of described operational amplifier II is connected with the base stage of triode M3, the collector of described triode M3 is connected with the base stage of triode M1 and collector, the negative electrode of described operational amplifier II is connected with the emitter of triode M3, and the emitter of described triode M3 is by resistance R1 ground connection; The base stage of described triode M1 is connected with the base stage of triode M2, and the emitter of described triode M1 is all connected with 15V power supply with the emitter of triode M2, and the collector of described triode M2 is connected with one end of resistance R in current integration circuit.
As a preferred embodiment of the present invention, to carry out capacitance voltage after detection reaches Umax, opening the opposite current circuit corresponding with input current signal by sequence circuit, closing input current simultaneously at thresholding control circuit, enter current integration circuit, make electric capacity carry out reverse charging; Reverse charging makes electric capacity both end voltage lower than after Umin, is controlled the input of current integration circuit by sequence circuit, closes back discharge electric current, opens input current, again charge to electric capacity; Control signal in sequence circuit exports the frequency signal corresponding with input current through process.
Compared with prior art, tool of the present invention has the following advantages:
1, break away from the dependence to sampling resistor, reduced the requirement to resistance, reduce installation cost, improve the stability of device simultaneously.
2, directly current signal is processed, reduce and the power consumption of tested circuit is affected, improve the accommodation of equipment.
3, have employed integrating circuit to current signal process, avoid using the AD conversion chip in conventional detection devices or V_F conversion chip, broken away from the impact of precision by chip restriction, reduced installation cost, and improve real-time and the accuracy of input.
4, have employed capacitance protection circuit, the reliability of device is got a promotion.
5, selected band-gap reference bias current sources as the constant current source of inside, the temperature characterisitic of device and stability are got a promotion.
Accompanying drawing explanation
Fig. 1 is the structured flowchart of Weak current signal supervisory instrument;
Fig. 2 is the structured flowchart of power frequency change-over circuit;
Fig. 3 is current integration circuit figure;
Fig. 4 is that thresholding controls and capacitor charging protection circuit figure;
Fig. 5 is constant-current source circuit figure;
Fig. 6 is the signal mode graphoid of power frequency change-over circuit.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.
As shown in Figure 1, Weak current signal supervisory instrument, comprises power frequency change-over circuit and its main operational circuit, current signal input current freq converting circuit, power frequency change-over circuit is converted to frequency signal input core computing circuit, then is exported by current value by its main operational circuit.
Power frequency change-over circuit comprises current integration circuit, thresholding controls and capacitor charging protection circuit, sequence circuit and constant-current source circuit, as shown in Figure 2.
As shown in Figure 3, current integration circuit comprises resistance R, operational amplifier I and electric capacity C to current integration circuit.Current signal is connected with one end of resistance R, and the other end of resistance R is all connected with the negative electrode of operational amplifier I with one end of electric capacity C, the plus earth of operational amplifier I.Adopt BiMOS operational amplifier 7F3140 as the amplifier part of integrating circuit, 7F3140 has high input impedance, low-down input current, lower specified input offset voltage.The computing formula of integrating circuit is: out_V=1/C* ∫ in_I*dt.
Thresholding control and capacitor charging protection circuit are as shown in Figure 4; thresholding controls and capacitor charging protection circuit comprises diode VZ, diode VF, resistance RZ1, resistance RZ2, resistance RM1, resistance RM2, resistance RF1, resistance RF2, resistance RM3, resistance RM4, triode VZT and triode VFT.The output terminal of operational amplifier I is connected with the positive pole of diode VZ and the negative pole of diode VF respectively, the base stage of the negative pole connecting triode VZT of diode VZ, the collector of triode VZT is connected with+5V power supply, the emitter of described triode VZT is connected with one end of resistance RZ2, one end of resistance RZ1 is connected with the base stage of triode VZT, and the other end of resistance RZ1 is connected with the collector of triode VZT.The positive pole of diode VF is connected with the base stage of triode VFT, the collector of triode VFT is connected with-5V power supply, the emitter of triode VFT is connected with one end of resistance RF2, and one end of resistance RF1 is connected with the base stage of triode VFT, and the other end of resistance RF1 is connected with the collector of triode VFT.One end of resistance RM1 is connected with the collector of triode VZT, and the other end of resistance RM1 is connected with one end of resistance RM2, and one end of resistance RM4 is connected with the collector of triode VFT, and the other end of resistance RM4 is connected with one end of resistance RM3.The other end of resistance RZ2 is connected with the other end of resistance RF2, the other end of resistance RM2 is connected with the other end of resistance RM3, and the other end of resistance RZ2 is connected with the other end of electric capacity C with the other end of resistance RM3 respectively with the other end of resistance RF2 and the other end of resistance RM2.Thresholding control and the Main Function of capacitor charging protection circuit be prevent integrating circuit discharge and recharge excessively, external out gate limited signal simultaneously.Thresholding control circuit main operational principle: when input signal enters circuit, carries out forward and reverse shunting by two diodes (VZ, VF) to signal; Positive signal enters the base stage of triode VZT, and negative signal enters the base stage of triode VFT; When the charging of forward (oppositely) signal acquires a certain degree, triode VZT(VFT) cut-off, make circuit stop charging to electric capacity C; Prevent electric capacity C overcharged, cause capacitance damage.
The CPLD(XC9536 of what the control chip of sequence circuit adopted is Xilinx), the I/O interface of this chip is accessed in the other end of resistance RM1 and one end of resistance RM2.The I/O interface of this chip is accessed in the other end of resistance RM4 and one end of resistance RM3.
As shown in Figure 5, constant-current source circuit comprises operational amplifier II, triode M1, triode M2, triode M3 and resistance R1 to constant-current source circuit.The anode of operational amplifier II is connected with 10V power supply, the output terminal of operational amplifier II is connected with the base stage of triode M3, the collector of triode M3 is connected with the base stage of triode M1 and collector, the negative electrode of operational amplifier II is connected with the emitter of triode M3, and the emitter of triode M3 is by resistance R1 ground connection.The base stage of triode M1 is connected with the base stage of triode M2, and the emitter of triode M1 is connected with 15V power supply with the emitter of triode M2, and the collector of triode M2 is connected with one end of resistance R in current integration circuit by analog switch.
The principle of work of power frequency change-over circuit is as follows:
1, first current signal enters current integration circuit, and by current integration circuit, at electric capacity two ends, charging produces voltage.
2, by thresholding control circuit, capacitance voltage is detected, reach Umax(by circuit design threshold value) after open the opposite current circuit corresponding with input current signal by sequence circuit, close input current simultaneously, enter current integration circuit, make electric capacity carry out reverse charging.
3, when reverse charging makes electric capacity both end voltage lower than Umin(by circuit design threshold value) after, controlled the input of integrating circuit by sequence circuit, close back discharge electric current, open input current, again electric capacity is charged.
4, repeat the step of 1-3, the control signal in sequence circuit is exported through process, then becomes the frequency signal corresponding with input current.
5, in charge and discharge process, do not respond in time if there is sequence circuit, then overcharging probably appears in electric capacity, causes the overtension at electric capacity two ends, and then damages circuit.So add capacitor charging protection circuit in current integration circuit, prevent electric capacity from overcharging, concrete protection circuit is shown in Fig. 4.
The signal imitation of power frequency change-over circuit is as Fig. 6, and as can be seen from Fig. 6, the cycle of gating pulse is subject to the impact of input current signal I_in size.
The control chip of sequence circuit supports parallel processing, can detect simultaneously, control, and each other without delay, can be good at the requirement of real-time meeting system to multiple signals; The pin time delay of this chip is very short simultaneously, can carry out rapid reaction, makes system have good real-time and accuracy.Threshold detection in program design adopts along trigger mode, in order to remove the impact of noise, adding software filtering in a program, improve detection degree of accuracy; In order to remove the impact of input signal on reverse charging, in a program corresponding control is done to the opening and closing of input signal, make the impact of system only by single signal during charging and discharging, do not make the result of measurement occur relatively large deviation by the interference between signal.
Constant-current source circuit Major Difficulties is to need this current source designs to become not by the stable constant current source that resistance and temperature affect.What this circuit adopted is the main power source chip of band-gap reference bias current sources as constant current source, and the constant current source designed like this has good temperature characterisitic and stability, makes the temperature characterisitic of entire system and stability have larger lifting.The precision of constant current source is determined by the precision of reference source output voltage, and its temperature coefficient is very little, meet the requirement of system hypothermia drift, as long as have high-precision reference source simultaneously, just can improve the steady current of degree of precision, be that system can obtain higher measuring accuracy.
Its main operational circuit adopts single-chip microcomputer or DSP to gather frequency signal, then utilizes correlation parameter and algorithm to carry out computing, frequency signal is converted into corresponding current value, external output display.Here require that the frequency acquisition of single-chip microcomputer or DSP is higher than the frequency of frequency signal.The current value conversed like this is just more accurate.
This device make use of the characteristic of capacitor charge and discharge, by tiny signal through current integration circuit, the threshold value of setting whether is reached through the discharge and recharge of thresholding control circuit Detection capacitance, the input of current signal and reverse discharge current is controlled by sequence circuit, electric capacity is changed between charging and discharging, forms the frequency signal corresponding with size of current; Current value corresponding to frequency signal convert to by its main operational circuit to export.This device can be real-time the current value detecting Weak current, more existing current detection circuit has higher stability, real-time, and advantage of lower cost, wide accommodation.
What finally illustrate is, above embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although with reference to preferred embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that, can modify to technical scheme of the present invention or equivalent replacement, and not departing from aim and the scope of technical solution of the present invention, it all should be encompassed in the middle of right of the present invention.
Claims (2)
1. Weak current signal supervisory instrument, comprise power frequency change-over circuit and its main operational circuit, current signal input current freq converting circuit, power frequency change-over circuit is converted to frequency signal input core computing circuit, by its main operational circuit, current value is exported again, it is characterized in that: described power frequency change-over circuit comprises current integration circuit, thresholding controls and capacitor charging protection circuit, sequence circuit and constant-current source circuit;
Described current integration circuit comprises resistance R, operational amplifier I and electric capacity C; One end of current signal input resistance R, the other end of described resistance R is all connected with the negative electrode of operational amplifier I with one end of electric capacity C, the plus earth of described operational amplifier I;
Described thresholding controls and capacitor charging protection circuit comprises diode VZ, diode VF, resistance RZ1, resistance RZ2, resistance RM1, resistance RM2, resistance RF1, resistance RF2, resistance RM3, resistance RM4, triode VZT and triode VFT; The output terminal of described operational amplifier I is connected with the positive pole of diode VZ and the negative pole of diode VF respectively, the base stage of the negative pole connecting triode VZT of described diode VZ, the collector of described triode VZT is connected with+5V power supply, the emitter of described triode VZT is connected with one end of resistance RZ2, one end of described resistance RZ1 is connected with the base stage of triode VZT, and the other end of described resistance RZ1 is connected with the collector of triode VZT; The positive pole of described diode VF is connected with the base stage of triode VFT, the collector of described triode VFT is connected with-5V power supply, the emitter of described triode VFT is connected with one end of resistance RF2, one end of described resistance RF1 is connected with the base stage of triode VFT, and the other end of described resistance RF1 is connected with the collector of triode VFT; One end of described resistance RM1 is connected with the collector of triode VZT, and the other end of described resistance RM1 is connected with one end of resistance RM2, and one end of described resistance RM4 is connected with the collector of triode VFT, and the other end of resistance RM4 is connected with one end of resistance RM3; The other end of described resistance RZ2 is connected with the other end of resistance RF2, the other end of described resistance RM2 is connected with the other end of resistance RM3, and the other end and the resistance RM2 of described resistance RZ2 and resistance RF2 are connected with the other end of electric capacity C respectively with the other end of resistance RM3;
The CPLD of what the control chip of described sequence circuit adopted is Xilinx, the I/O interface of this chip is accessed in the other end of described resistance RM1 and one end of resistance RM2; The I/O interface of this chip is accessed in the other end of described resistance RM4 and one end of resistance RM3;
Described constant-current source circuit comprises operational amplifier II, triode M1, triode M2, triode M3 and resistance R1; The anode of described operational amplifier II is connected with 10V power supply, the output terminal of described operational amplifier II is connected with the base stage of triode M3, the collector of described triode M3 is connected with the base stage of triode M1 and collector, the negative electrode of described operational amplifier II is connected with the emitter of triode M3, and the emitter of described triode M3 is by resistance R1 ground connection; The base stage of described triode M1 is connected with the base stage of triode M2, and the emitter of described triode M1 is all connected with 15V power supply with the emitter of triode M2, and the collector of described triode M2 is connected with one end of resistance R in current integration circuit.
2. Weak current signal supervisory instrument according to claim 1, it is characterized in that: capacitance voltage carried out after detection reaches Umax at thresholding control circuit, the opposite current circuit corresponding with input current signal is opened by sequence circuit, close input current simultaneously, enter current integration circuit, make electric capacity carry out reverse charging; Reverse charging makes electric capacity both end voltage lower than after Umin, is controlled the input of current integration circuit by sequence circuit, closes back discharge electric current, opens input current, again charge to electric capacity; Control signal in sequence circuit exports the frequency signal corresponding with input current through process.
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| CN201310743456.2A CN103713181B (en) | 2013-12-30 | 2013-12-30 | Weak current signal supervisory instrument |
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| CN201310743456.2A CN103713181B (en) | 2013-12-30 | 2013-12-30 | Weak current signal supervisory instrument |
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| CN103713181B true CN103713181B (en) | 2016-03-09 |
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| CN104597316A (en) * | 2015-01-08 | 2015-05-06 | 聚光科技(杭州)股份有限公司 | Weak current detecting device and method |
| CN104793045B (en) * | 2015-04-23 | 2016-10-26 | 中国科学院近代物理研究所 | A kind of wide-range current frequency converter |
| CN106888022A (en) * | 2015-12-15 | 2017-06-23 | 航天科工惯性技术有限公司 | A kind of high-resolution current/frequency conversion circuit |
| CN106053930B (en) * | 2016-07-06 | 2018-11-23 | 西北核技术研究所 | A kind of anti-random noise without switch weak signal synchronous integration measuring device and measuring method |
| CN107765075B (en) * | 2016-08-16 | 2021-08-24 | 中兴通讯股份有限公司 | Current signal processing device |
| CN107238746B (en) * | 2017-06-14 | 2020-06-05 | 国网河南省电力公司电力科学研究院 | Micro-current measuring circuit for dielectric response test |
| CN107703351B (en) * | 2017-09-27 | 2020-12-04 | 成都兴睿宝电子科技有限公司 | Large dynamic micro-current detection circuit |
| CN108900194A (en) * | 2018-09-26 | 2018-11-27 | 北方电子研究院安徽有限公司 | A kind of power frequency conversion circuit that programmable multi-threshold compares |
| CN110058078A (en) * | 2019-05-23 | 2019-07-26 | 上海仁机仪器仪表有限公司 | A kind of current measurement circuit and measurement method based on I-F transformation |
| CN112485494A (en) * | 2020-11-17 | 2021-03-12 | 天津津航计算技术研究所 | Current detection circuit based on triode |
| CN114325043B (en) * | 2021-12-16 | 2023-10-17 | 华人运通(江苏)技术有限公司 | System and method for improving small current test precision |
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