CN205484500U - Portable current measurement circuit that declines - Google Patents
Portable current measurement circuit that declines Download PDFInfo
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- CN205484500U CN205484500U CN201520976053.7U CN201520976053U CN205484500U CN 205484500 U CN205484500 U CN 205484500U CN 201520976053 U CN201520976053 U CN 201520976053U CN 205484500 U CN205484500 U CN 205484500U
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Abstract
The utility model relates to a little current measurement circuit specifically indicates little current measurement circuit of an electric chemical instrumentation etc. Relates to little weak electric signal's detection technical field. It includes resistor R1, R2, R3, R4, R5, R6, equivalent RX, an operational amplifier U1, and circuit connection is made to the 2nd operational amplifier U2 and change over switch S1 and power, an operational amplifier U1 is divided into two tunnel fortune and puts U1A and U1B, ua is U1A's output, and ub is U1B's positive going input end, constitute the adder by resistor R1, R2, R3, R4 and an operational amplifier U1A, an operational amplifier U1B is first follower, and the 2nd operational amplifier U2 is the second follower, change over switch S1 one end is connected with the ub end, and the other end is connected with resistor R5 or resistor R6 respectively. The utility model discloses a single mains operated, the device of low -power consumption has wide application prospect in portable instrument.
Description
Technical field
This utility model relates to the detection technique field of ultra-weak electronic signal, refers specifically to the portable micro current circuit of a kind of electrochemical apparatus etc..
Background technology
Along with development in science and technology, the important means having become further learning to Understand Nature is measured in test under maximum conditions, measure in these tests is all some very weak physical quantitys, the most weak magnetic, weak sound, the low light level, weak vibration, weak bio signal etc., carry out I/V electricity conversion owing to these faint signals are typically all by sensor, make weak signal to be measured be converted into the signal of telecommunication.During actual measurement, noise and interference cannot be avoided, and have impact on sensitivity and the accuracy of measurement.
Measuring for the purpose of pA level electric current by research, the micro current instrument that precision is 0.5 grade is designed in exploitation, and the minimum zone of measurement is 1pA, for pA level current measurement, measuring circuit cannot Direct Acquisition current signal, need to carry out I/V conversion.Need to further be amplified for the voltage signal after conversion, otherwise can be disturbed by the offset voltage of operational amplifier, these direct current signals of bias current.Problematically, while amplifying capture measured signal, the impurity signal such as Hz noise, noise, circuit imbalance is exaggerated, and is filtered so needing to design relevant subsequent conditioning circuit, removes the most simultaneously.Generally for Hz noise, by taking shielding, filtering.And for the elimination of these direct current impurity signal such as circuit imbalance, become new research topic.
Utility model content
The purpose of this utility model is to eliminate clutter, interference source signal, to reach precise and stable measurement weak current, proposes the measuring circuit of a kind of portable electric current that declines.
This utility model based on traditional I/V change-over circuit along with the measurement of micro-electric current, can be because increasing feedback resistance, cause noise, cause the imbalance of amplifier, increase the error measured, and use adder principle, directly flow through, by producing weak current, the voltage that the generation of big resistance is corresponding, it is then passed through a micro-current follower, reaches preferable measurement effect.
The measuring circuit operation principle (as shown in Figure 1) of a kind of portable electric current that declines of this utility model is summarized as follows:
The measuring circuit of a kind of portable electric current that declines, including resistor R1, R2, R3, R4, R5, R6, equivalence RX, the first operational amplifier U1, wherein U1 is divided into two-way amplifier U1A and U1B, the second operational amplifier U2 and switching switch S1 and power supply to make circuit connection.
Described RX is the equivalent resistor of circuit to be measured.
First, according to adder principle, resistor R1, R2, R3, R4 and the first operational amplifier U1A adder is constituted.
Described resistor R1, R2 are in order to determine the Control of Voltage gain of amplifying circuit, as R1=R2=R3=R4, and the output Ua=Ui+Uc of the first operational amplifier U1A.
First operational amplifier U1B is the first follower, and Ub is the input of the first follower, and Uc is the output of the first follower, then Uc=Ub.
Secondly, equivalence RX is between Ua and Ub.According to the principle that flows to of current potentials, the electric current of equivalent resistor RX is flowed to Ub by Ua, and electric current is Iab, according to Ohm's law Iab=(Ua Ub)/RX, learns Ua=Ui+Uc, Ub=Uc from above-mentioned；Then Iab=Ui/RX.
Second operational amplifier U2 is the second follower, and Ub is the input of the second follower, and Uo is the output of the second follower.
According to follower principle Uo=Ub.According to Ohm's law Ub=Iab*R6；So Uo=Iab*R6；According to above-mentioned Iab=Ui/RX, then Uo=Ui/RX*R6.
Again, arranging switching switch S1 according to the range measured, switching switch S1 one end is connected with Ub end, and the other end is connected with R5 or R6.
Selection according to Ui and RX can produce the most small electric current, flows through R6, measures Uo according to the value of R6 and can accurately measure Iab.
According to the feature of amplifier LMC6001, its maximum Ib is just 25fA, electric current input noise just 0.13fA/ √ Hz, it is possible to accurately detect the current detecting of pA level.
In sum, the measuring circuit of a kind of portable electric current that declines of this utility model, use adder principle, directly flow through, by producing weak current, the voltage that the generation of big resistance is corresponding, be then passed through a micro-current follower, reached preferable measurement effect.
Accompanying drawing explanation
Fig. 1 is the measuring circuit schematic diagram of a kind of portable electric current that declines of this utility model；
Fig. 2 is the design sketch of this utility model embodiment 1pA test.
Detailed description of the invention
Below in conjunction with drawings and Examples, the utility model will be further described
Embodiment, applies measuring circuit in trace dissolved oxygen, makees circuit including resistor R1, R2, R3, R4, R5, R6, equivalence RX, the first operational amplifier U1, the second operational amplifier U2 and switching switch S1 and power supply and connects.
Wherein,
First operational amplifier U1 is divided into two-way amplifier U1A and U1B,
Adder is constituted by resistor R1, R2, R3, R4 and the first operational amplifier U1A.
First operational amplifier U1B is the first follower, and input is Ub, and outfan is Uc.
Second operational amplifier U2 is the second follower, and input is Ub, and outfan is Uo.
Switching switch S1 one end is connected with Ub end, and the other end is connected with R5 or R6.
Wherein, Ui is from 600 to 800mV；
Resistor R1=R2=R3=R4, resistance is from 10K Ω to 1M Ω；Resistor R6, resistance is from 100K Ω to 10G Ω, power supply VCC, voltage 3.3V to 15V.
Described first operational amplifier U1, the second operational amplifier U2, select that input bias current is less meets fA level requirement.
Described switching switch S1 uses SW SPDT.
Ua and Ub draws two binding posts, and wherein, Ua terminal connects the anode of oligodynamical oxygen electrode, and Ub terminal connects the negative electrode of oligodynamical oxygen electrode；Equivalence RX is replaced by oligodynamical oxygen electrode.
The weak current produced when oligodynamical oxygen electrode flows through resistor R6, detects Uo and just can carry out the detection of trace dissolved oxygen electric current Iab.
According to Iab=Uo/R6, Ui=1mV, R5=R6=1G Ω；Detection Uo=1mV, convert Iab=1pA.
Its effect (as shown in Figure 2).
In sum, a kind of portable micro current circuit of this utility model, based on adder principle, directly flow through, by producing weak current, the voltage that the generation of big resistance is corresponding, the circuit being then passed through a micro-current follower etc. connects.Employing single supply is powered, and selects the device of common low-power consumption, has broad application prospects in portable instrument.
Claims (3)
1. a portable micro current circuit, it is characterised in that include that resistor R1, R2, R3, R4, R5, R6, equivalence RX, the first operational amplifier U1, the second operational amplifier U2 and switching switch S1 and power supply are made circuit and connected；
Wherein, the first operational amplifier U1 is divided into two-way amplifier U1A and U1B；
Ua is the outfan of U1A, and Ub is the positive input of U1B；
Adder is constituted by resistor R1, R2, R3, R4 and the first operational amplifier U1A；
First operational amplifier U1B is the first follower, and the second operational amplifier U2 is the second follower；
Switching switch S1 one end is connected with Ub end, and the other end is connected with resistor R5 or resistor R6.
A kind of portable micro current circuit the most as claimed in claim 1, it is characterised in that
The input of described circuit is Ui；
The input of described first follower is Ub, and outfan is Uc；
The input of described second follower is Ub, and outfan is Uo；
Described equivalence RX is between Ua and Ub；
Described resistor R1, R2 are in order to determine the Control of Voltage gain of amplifying circuit, as resistor R1=R2=R3=R4, and the output Ua=Ui+Uc of the first operational amplifier U1A.
A kind of portable micro current circuit the most as claimed in claim 1 or 2, it is characterised in that described resistor R1=R2=R3=R4, resistance: 10K Ω to 1M Ω；
Described resistor R5, R6 resistance: 100K Ω to 10G Ω；
Described equivalence RX is the equivalent resistor of circuit to be measured；
Described power supply VCC, magnitude of voltage: 3.3V to 15V；
Described first operational amplifier U1, the second operational amplifier U2, select that input bias current is less meets fA level requirement；
Described switching switch S1 uses SW-SPDT.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201520976053.7U CN205484500U (en) | 2015-11-30 | 2015-11-30 | Portable current measurement circuit that declines |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201520976053.7U CN205484500U (en) | 2015-11-30 | 2015-11-30 | Portable current measurement circuit that declines |
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| Publication Number | Publication Date |
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| CN205484500U true CN205484500U (en) | 2016-08-17 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201520976053.7U Active CN205484500U (en) | 2015-11-30 | 2015-11-30 | Portable current measurement circuit that declines |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105510674A (en) * | 2015-11-30 | 2016-04-20 | 上海仪电科学仪器股份有限公司 | Microcurrent measuring circuit |
| CN109709151A (en) * | 2019-01-30 | 2019-05-03 | 南通大学 | A kind of thin dielectric film electrical properties measuring system |
-
2015
- 2015-11-30 CN CN201520976053.7U patent/CN205484500U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105510674A (en) * | 2015-11-30 | 2016-04-20 | 上海仪电科学仪器股份有限公司 | Microcurrent measuring circuit |
| CN109709151A (en) * | 2019-01-30 | 2019-05-03 | 南通大学 | A kind of thin dielectric film electrical properties measuring system |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant |