CN103792409A - Measuring circuit for quickly-changed high currents - Google Patents
Measuring circuit for quickly-changed high currents Download PDFInfo
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- CN103792409A CN103792409A CN201410021869.4A CN201410021869A CN103792409A CN 103792409 A CN103792409 A CN 103792409A CN 201410021869 A CN201410021869 A CN 201410021869A CN 103792409 A CN103792409 A CN 103792409A
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- sensitive element
- compensating
- value
- operational amplifier
- resistance
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Abstract
The invention discloses a measuring circuit for quickly-changed high currents. The measuring circuit comprises a sensitive element and an operational amplifier. The sensitive element is connected in a measured current loop in series. The values of the sensitive element comprise a resistance value and an inductance value. The signal output end of the operational amplifier is connected with an oscilloscope. The measuring circuit further comprises a compensating circuit. The compensating circuit comprises a compensating resistor and a compensating capacitor, and the compensating resistor and the compensating capacitor are connected in series and then are connected with the sensitive element in parallel. The in-phase input end of the operational amplifier is connected between the compensating resistor and the compensating capacitor. The inverted input end of the operational amplifier is connected to the negative electrode of the measured current loop. The compensating condition of the compensating circuit is that the inductance value of the sensitive element/the resistance value of the sensitive element=the value of the compensating resistor*the value of the compensating capacitor, and the value of the compensating resistor is larger than the resistance value of the sensitive element. The measuring circuit can measure the quickly-changed high currents with the current values of 1 ampere to 100, 000 amperes, the change frequency of the high currents reaches 109 HZ/s, the waveform of the high currents is free, and the measuring precision of the measuring circuit can reach one in a million.
Description
Technical field
The present invention relates to the metering circuit of fast-changing large electric current.
Background technology
Modern control technology has been applied to each aspect of modern advanced country, industry, agricultural, communications and transportation, national defence etc.There is no modern advanced country without modern control technology, and will control well and accurately, first need to measure soon and accurately.
In modern control technology, to electric control and important, good electric control needs the measurement of accurate electricity at a high speed, comprises the measurement to voltage, electric current.For example, at some special occasions: accurate electric welding machine, large-scale military equipment all need fast-changing large electric current to measure accurately.Accurate measurement could produce accurate control.Variation generally refers to the variation of large electric current in millisecond fast.
The measuring method of fast-changing large electric current at present, substantially divide two kinds:
1, direct series process.By the current sensitive element access current return of directly connecting, utilize electric current to measure in the ohmically voltage drop of sensitive element.But because current sensitive device is except useful resistance, always with inductance, this makes not only to comprise in pressure drop resistance drop, also comprise inductive drop, when curent change is fast, inductive drop is very large, make to measure at a high speed large electric current time error very large, measuring accuracy is difficult to reach 2%.
2, contactless.Actual is to measure current field, and it can only be measured change frequency and be up to per second 10
6the large electric current of HZ, measuring accuracy is difficult to reach 1%.
Summary of the invention
The technical problem to be solved in the present invention is to provide one can measure current value and be up to per second 10 at 1-100000 ampere, change frequency
9hZ, waveform are the metering circuit of fast-changing large electric current arbitrarily, its measuring accuracy can reach ten thousand/.
Technical solution of the present invention is, a kind of metering circuit of the fast-changing large electric current with following structure is provided, and comprises sensitive element and operational amplifier; Described sensitive element is connected in tested current return; The value of described sensitive element comprises resistance value and inductance value; The signal output part of described operational amplifier connects oscillograph; Described metering circuit also comprises compensating circuit; Described compensating circuit comprises compensating resistance and building-out capacitor, in parallel with described sensitive element after described compensating resistance and building-out capacitor series connection; The in-phase input end of described operational amplifier is connected between described compensating resistance and building-out capacitor; The inverting input of described operational amplifier is connected to the negative pole of tested current return; The compensation condition of described compensating circuit is: the value of the building-out capacitor described in the value * of the compensating resistance of the resistance value of the sensitive element of the inductance value of described sensitive element/described=described, the resistance value of the sensitive element described in the value >> of described compensating resistance.
Adopt after above structure, the metering circuit of fast-changing large electric current of the present invention, compared with prior art, has the following advantages:
The metering circuit of the fast-changing large electric current of the present invention also belongs to series connection pressure decline method in essence, but add after compensating circuit, adopt in this way, fast-changing current waveform is converted to the fast-changing voltage waveform on building-out capacitor exactly, as long as keep the value of the electric capacity described in the value * of resistance of the resistance value of the sensitive element of the inductance value of described sensitive element/described=described, the resistance value of the sensitive element described in the value >> of described resistance, this metering circuit just can be used for measure nanosecond change up to 100000A electric current, not only accurately but also response fast, the waveform of oscilloscope display is closer to actual waveform.
As another kind of improvement of the present invention, the value * S of the building-out capacitor described in the input impedance >>1/ of the inverting input of described operational amplifier, the passband >1GHZ of described operational amplifier.Adopt after this kind of structure, the waveform of oscilloscope display is more close to actual waveform.
Accompanying drawing explanation
Fig. 1 is the circuit structure diagram of the metering circuit of fast-changing large electric current of the present invention.
Fig. 2 is the electrical block diagram that the belt current of the metering circuit of fast-changing large electric current of the present invention flows to.
Shown in figure: 1, sensitive element, 2, operational amplifier, 3, compensating circuit, 4, oscillograph.
embodiment
Below in conjunction with the drawings and specific embodiments, the invention will be further described.
Refer to shown in Fig. 1, the metering circuit of fast-changing large electric current of the present invention comprises sensitive element 1, operational amplifier 2 and compensating circuit 3.Described sensitive element 1 can be large-current electric resistive current sensitive element arbitrarily, as long as internal resistance is little, temperature coefficient is little.In the world, the large-current electric resistive current sensitive element that a lot of companies produce can use.In this specific embodiment, described sensitive element adopts the part no:3020-01105 element of DATEL company of the U.S..
Described sensitive element 1 is connected in tested current return.The value of described sensitive element 1 comprises resistance value and inductance value.Described compensating circuit 3 comprises compensating resistance and building-out capacitor, in parallel with described sensitive element 1 after described compensating resistance and building-out capacitor series connection.The in-phase input end of described operational amplifier 2 is connected between described compensating resistance and building-out capacitor.The reverse input end of described operational amplifier 2 is connected to the negative pole in circuit-under-test loop.The signal output part of described operational amplifier 2 connects oscillograph 4.
The compensation condition of described compensating circuit 3 is: the value of the building-out capacitor described in the value * of the resistance of the resistance value of the sensitive element of the inductance value of described sensitive element/described=described, the resistance value of the sensitive element described in the value >> of described compensating resistance.(about 10
7doubly)
The value * S of the building-out capacitor described in the input impedance >>1/ of the inverting input of described operational amplifier 2, the passband >1GHZ of described operational amplifier.(S=j ω=j6.2832f, f is frequency, the measuring speed of wishing.）
Refer to shown in Fig. 2, the measuring principle of the metering circuit of fast-changing large electric current of the present invention is as follows:
Under most of occasions, sensitive element is the sheet metal of the temperature coefficient of about 50 micro-ohms (50 μ Ω) very little (0.002%/℃), but still (can calculate according to physical equation, be generally 10 – 30 nH, n=10 with small inductor
-9) such small inductor, from U=Ldi/dt, at di=100A, dt=10
-5when s, U
l=20*10
-9* 100/10
-5=0.2 V, when being far longer than electric current and being 1000A, the voltage drop U producing on resistance
r=1000A*50*10
-6=0.05V, visible, do not adopt some special measures, with above sensitive element, be the initial waveform that cannot accurately measure fast-changing large electric current.
In this specific embodiment, the sensitive element adopting is to adopt electric current sensor element: DATEL company of the U.S., RC electronics, inc. all produces resistance type current sensor.For example: the part no:3020-01105 element of DATEL company, when its 1000A, produce 50mV pressure drop, according to its profile, can estimate that with physical equation its inductance is approximately worth, metering circuit of the present invention compensates:
If the resistance value of described sensitive element is R1; The inductance value of described sensitive element is L; The value of described compensating resistance is R2; The value of described building-out capacitor is C.
In actual applications, be exemplified below:
V=250V, Ri=50 m Ω, I=5000A square wave, and make L/R
1=R
2c, R
2>>R
1, get R2=10
7r1,
R1=50μΩ?，R2=500?Ω，L=13?nH，C=0.52μF
1. when uncompensated, be only L, R1 connects with power supply, and measuring-signal is V
00
2. while having compensation, be that (L+R1) is first in parallel with (R2+C), and then connect with power supply, measuring-signal is V
0
The compensation condition requiring is: L/R
1=R
2c, R2>>R1
Its measuring-signal is
Two measuring-signals can be streamlined any further (Ri>>R1), after simplification, compare again
A does not compensate
Can be reduced to
voo=VR1*(1+T old s)/Ri
B has compensation
Can be reduced to
vo=VR1/Ri
C ideal current (not accessing before sensor)
After access resistance sensor, wish: ideal square wave
Can be reduced to
vout=VR1/Ri
Consider again actual parameter Ri=50 m Ω, R1=50u Ω
Relatively the simplification expression formula of Voo, Vo, Vout, can find: Vo, Vout are duplicate.And the molecule of Voo many a factor (1+T
olds), this means the time that uncompensated Voo need to be longer, and output Voo just can reach high precision district.This is a very large distortion to fast-changing large electric current.Here it is, and why uncompensated circuit can not be measured the large electric current changing at a high speed.
That is to say: V
00transient process be T
old=0.26mS can only measure mS level curent change.V
0transient process be 10
7hurry up, its T=10
-7t
old=0.26*10
-10s, so circuit can be surveyed the electric current that nanosecond changes after compensation.
Visible, there is the signal V after compensation
0closer to ideal waveform: V
reason=V/Ri (R1<<Ri).That is to say, more accurately more response is fast than Voo for Vo.
Conclusion:
Adopt after compensation method of the present invention, when use, as long as keep L/R
1=R
2c, R2>>R1, and to the requirement of operational amplifier be: the input impedance R of the inverting input of described operational amplifier
iG>>1/CS, (S=j ω=j6.2832f, f is frequency, the measuring speed of wishing), the passband >1GHZ of described operational amplifier.This circuit can be used for measuring the large electric current (2-10000A) that nanosecond changes.If change sensitive element, even can measure that nanosecond changes up to 100000A electric current, not only accurately but also response fast, the waveform of oscilloscope display is far away closer to actual waveform.Be adapted to especially require accurately to control the occasion of rapid large-current.
Claims (2)
1. a metering circuit for fast-changing large electric current, comprises sensitive element (1) and operational amplifier (2); Described sensitive element (1) is connected in tested current return; The value of described sensitive element (1) comprises resistance value and inductance value; The signal output part of described operational amplifier (2) connects oscillograph (4); It is characterized in that: described metering circuit also comprises compensating circuit (3); Described compensating circuit (3) comprises compensating resistance and building-out capacitor, in parallel with described sensitive element (1) after described compensating resistance and building-out capacitor series connection; The in-phase input end of described operational amplifier (2) is connected between described compensating resistance and building-out capacitor; The inverting input of described operational amplifier (2) is connected to the negative pole of tested current return; The compensation condition of described compensating circuit (3) is: the value of the building-out capacitor described in the value * of the compensating resistance of the resistance value of the sensitive element of the inductance value of described sensitive element/described=described, the resistance value of the sensitive element described in the value >> of described compensating resistance.
2. the metering circuit of fast-changing large electric current according to claim 1, it is characterized in that: the value * S of the building-out capacitor described in the input impedance >>1/ of the inverting input of described operational amplifier (2), the passband >1GHZ of described operational amplifier (2).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410021869.4A CN103792409B (en) | 2014-01-18 | 2014-01-18 | The measuring circuit of fast-changing large electric current |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410021869.4A CN103792409B (en) | 2014-01-18 | 2014-01-18 | The measuring circuit of fast-changing large electric current |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103792409A true CN103792409A (en) | 2014-05-14 |
| CN103792409B CN103792409B (en) | 2016-05-11 |
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ID=50668276
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410021869.4A Active CN103792409B (en) | 2014-01-18 | 2014-01-18 | The measuring circuit of fast-changing large electric current |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108693394A (en) * | 2017-04-12 | 2018-10-23 | 上海西门子医疗器械有限公司 | The tube current computational methods and equipment of X-ray bulb |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59126961A (en) * | 1983-01-12 | 1984-07-21 | Fujitsu Ltd | Measuring device of large current |
| CN102445588A (en) * | 2011-11-23 | 2012-05-09 | 中国人民解放军海军工程大学 | Short-time slowly-varying large-current measuring device based on PCB type Rogowski coil |
-
2014
- 2014-01-18 CN CN201410021869.4A patent/CN103792409B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59126961A (en) * | 1983-01-12 | 1984-07-21 | Fujitsu Ltd | Measuring device of large current |
| CN102445588A (en) * | 2011-11-23 | 2012-05-09 | 中国人民解放军海军工程大学 | Short-time slowly-varying large-current measuring device based on PCB type Rogowski coil |
Non-Patent Citations (3)
| Title |
|---|
| 张建永 等: "一种测量脉冲大电流的改进分流器设计", 《电子测量技术》 * |
| 李维波 等: "陡脉冲大电流的Rogowski测量线圈仿真研究", 《高电压技术》 * |
| 韩勇兵: "如何实现快速变化的阶梯电流的测量", 《计量与测试技术》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108693394A (en) * | 2017-04-12 | 2018-10-23 | 上海西门子医疗器械有限公司 | The tube current computational methods and equipment of X-ray bulb |
| CN108693394B (en) * | 2017-04-12 | 2020-06-26 | 上海西门子医疗器械有限公司 | Tube current calculation method and device of X-ray bulb tube |
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| Publication number | Publication date |
|---|---|
| CN103792409B (en) | 2016-05-11 |
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