CN101285852B - Alternating current voltage electric current converter and device and method for testing alternating-current small ammeter - Google Patents
Alternating current voltage electric current converter and device and method for testing alternating-current small ammeter Download PDFInfo
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- CN101285852B CN101285852B CN2008101126567A CN200810112656A CN101285852B CN 101285852 B CN101285852 B CN 101285852B CN 2008101126567 A CN2008101126567 A CN 2008101126567A CN 200810112656 A CN200810112656 A CN 200810112656A CN 101285852 B CN101285852 B CN 101285852B
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Abstract
An alternating voltage-current converter comprises a standard capacitor and a meter amplifier, wherein the standard capacitor is set as an external connection type; the input bias current of the meter amplifier is less than 1pA, while the input impedance is more than 10<13> Ohm; the standard capacitor is connected with the meter amplifier through a fourwire access method. The fourwire access method is as follows: a capacitor end IH is used as an external voltage signal input end; a capacitor end VH is led to the positive input end of the meter amplifier; a capacitor end VL is connected with the negative input end of the meter amplifier; and a capacitor end IL is used as a signal output end. The alternating voltage-current converter adopts the standard capacitor to realize accurate conversion from alternating voltage to alternating current, and also provides a device and a method for realizing accurate verification of an AC small ammeter; moreover, the alternating voltage-current converter effectively solves the origin problem of AC low current.
Description
Technical field
The present invention relates to a kind of alternating voltage current converter of voltage current adapter technology, particularly a kind of pin-point accuracy and use this alternating voltage current converter accurately to examine and determine the device that 2 μ A-2mA/10Hz～10kHz exchange the method for little reometer and realize this method.
Background technology
Present alternating voltage current converter is generally the voltage current adapter that adopts the voltage resistance converter technique to realize, because the resistance value difference of high resistance resistor AC resistance under different frequency that this converter uses, and present resistance data of tracing to the source under 1kHz only, so there is the magnitude tracing problem that exchanges high value resistor, can't realize that alternating voltage arrives the accurate transformation of little electric current, simultaneously, the calibration method that exchanges little reometer at present mainly is to exchange shunt (AC resistance), measure the alternating voltage at its two ends, realize ac flow thereby calculate.Therefore the approach because AC resistance country's metering at present institute does not trace to the source adopts the AC resistance mode to examine and determine to exchange little reometer technical difficulty very big, also has a series of validation problem of tracing to the source.
Summary of the invention
Defective at the prior art existence, the invention provides a kind of alternating voltage current converter, adopt standard capacitance that voltage source accurately is converted to and exchange little electric current, the invention still further relates to the apparatus and method that calibrating exchanges little reometer, and effectively solved the problem of tracing to the source that exchanges little electric current.
Technical scheme of the present invention is:
A kind of alternating voltage current converter is characterized in that comprising standard capacitance, instrument amplifier, and described standard capacitance is set to circumscribed, and described standard capacitance is connected with instrument amplifier by four line access methods, and described four line access methods are capacitance terminal I
HAs the external voltage signal input end, with capacitance terminal V
HGuide to the instrument amplifier positive input, capacitance terminal V
LConnect the instrument amplifier reverse input end, capacitance terminal I
LAs signal output part, described instrument amplifier is three amplifier differential amplifiers, described three amplifier differential amplifiers comprise two prebuffers and the unity gain differential amplifier that links to each other with prebuffer, the input bias current＜1pA of described instrument amplifier, input impedance＞10
13Ω.
Above-mentioned standard capacitance is that four ends are to standard capacitance.
Two prebuffers provide unity gain for input difference voltage, the unity gain differential amplifier provides single ended output voltage over the ground, connect feedback resistance between described two prebuffers, the input bias current＜1pA of described prebuffer, input impedance＞10
13Ω; The gain error of described unity gain differential amplifier＜0.01%; Input offset voltage＜50uV; The V of described standard capacitance
HAnd V
LEnd connects the input end of two prebuffers.
Above-mentioned standard capacitance shell is made shield, and is connected with instrument amplifier by high insulation shielding cable.
Above-mentioned high insulation shielding cable is three coaxial teflon cables.
Also be provided with the equivalent potential screen circuit, described equivalent potential screen circuit is that two prebuffers are connected with a voltage follower separately, the output terminal of prebuffer is drawn the current potential that equates with the difference input of three amplifier differential amplifiers, and be connected respectively to the voltage follower input end, the output of described voltage follower connects the intershield layer of the input signal cable of prebuffer, input bias current＜the 1pA of described voltage follower, input impedance＞10
13Ω.
Adopt a kind of device that exchanges little reometer of examining and determine of above-mentioned alternating voltage current converter, it is characterized in that comprising standard voltage source, alternating voltage current converter, frequency meter and AC digital voltmeter, the forward end of described standard voltage source inserts capacitance terminal I
H, the backward end of standard voltage source and capacitance terminal I
LInsert the I of the little reometer of tested interchange respectively
LEnd and I
HEnd, described digital voltmeter links to each other with the output of instrument amplifier respectively with frequency meter.
The little reometer of above-mentioned tested interchange, instrument amplifier are connected computing machine by gpib interface respectively with frequency meter, and described computing machine calculates and demonstrate the alternating current flow valuve by the transitive relation of the conversion of the electric current and voltage between alternating voltage and the alternating current.
Adopt a kind of method that exchanges little reometer of examining and determine of above-mentioned alternating voltage current converter, it is characterized in that comprising the steps:
A, standard voltage source convert alternating current to by above-mentioned alternating voltage current converter, and described alternating current inputs to the little reometer of tested interchange;
B, the output of the instrument amplifier in the alternating voltage current converter is connected AC digital voltmeter and frequency meter respectively, and the alternating voltage by AC digital voltmeter measurement standard electric capacity two ends, AC current frequency measured by frequency meter;
C, the little reometer of tested interchange, instrument amplifier are connected computing machine by gpib interface respectively with frequency meter, and described computing machine calculates and demonstrate the alternating current flow valuve by the transitive relation of the conversion of the electric current and voltage between alternating voltage and the alternating current.
Technique effect:
A kind of alternating voltage current converter provided by the invention inserts instrument amplifier, the input bias current＜1pA of instrument amplifier, input impedance＞10 by the standard capacitance four line access methods that adopt circumscribed
13Ω, the instrument amplifier that employing has T Ω level input resistance and pA level bias current comes measurement standard electric capacity both end voltage, alternating voltage is converted to alternating current, adopt four ends can reduce external influence effectively, can guarantee the accuracy of alternating voltage current converter conversion effectively standard capacitance; Instrument amplifier is three amplifier differential amplifiers, the input bias current＜1pA of the prebuffer of three amplifier differential amplifiers, input impedance＞10
13Ω; The gain error of unity gain differential amplifier＜0.01%; Input offset voltage＜50uV, make voltage current adapter to the relative influence of measurement result less than 1 * 10
-6Greatly reduce standard capacitance simultaneously to impedance influences that goes between between standard voltage source and leakage contribution; Adopt the high insulated cable of three coaxial teflon as the connecting line material, its insulation resistance can reach 10
14Ω, the middle layer can be used as the equivalent potential screen layer, and the protection internal layer circuit reduces leakage current; Use equal potential screening technique, on the prebuffer of instrument amplifier, take out the equipotential signal of the difference input voltage of three amplifier differential amplifiers,, avoid the generation of leaking as the shielding of input height terminal voltage; Owing to used triaxial cable and connector Shielding Design, equal potential screening technique, the differential amplifying technique of three amplifiers etc., effectively reduced external disturbance and noise, guaranteed the accuracy and the stability of alternating voltage current converter.
The present invention examines and determine the device that exchanges little reometer, adopted the alternating voltage current converter that can accurately standard voltage source be converted to alternating current, comprise standard voltage source, the alternating voltage current converter, frequency meter and AC digital voltmeter, digital voltmeter links to each other with the output of instrument amplifier respectively with frequency meter, the little reometer of tested interchange, instrument amplifier is connected computing machine by gpib interface respectively with frequency meter, computing machine calculates and demonstrates the alternating current flow valuve by the transitive relation of the conversion of the electric current and voltage between alternating voltage and the alternating current and calibrates the little reometer of interchange, can accurately examine and determine the value that exchanges little reometer.Calibrating exchanges the method for little reometer, produces the little electric current of interchange of standard by voltage current adapter, standard voltage source, AC digital voltmeter and frequency meter, and calibrates the little reometer of interchange; The alternating voltage current converter is applied to standard voltage source on the standard capacitance, then with the voltage amplification at standard capacitance two ends and deliver to the interchange standard voltmeter, calibrate the little reometer of interchange by calculating the alternating current flow valuve, to exchange little electric current and be traceable on electric capacity, alternating voltage and the frequency, solve the problem of tracing to the source.
Description of drawings
Fig. 1 is the schematic diagram of alternating voltage current converter of the present invention;
Fig. 2 is the circuit diagram of the instrument amplifier of alternating voltage current converter of the present invention;
Fig. 3 is the theory diagram that the present invention examines and determine the device that exchanges little reometer;
Fig. 4 is the test data table that the present invention examines and determine the device that exchanges little reometer;
Fig. 5 is the relative expanded uncertainty table that the present invention examines and determine the device that exchanges little reometer.
Embodiment
The present invention is described further below in conjunction with accompanying drawing.
Fig. 1 is the schematic diagram of alternating voltage current converter of the present invention.A kind of alternating voltage current converter comprises standard capacitance, instrument amplifier, the input bias current＜1pA of the instrument amplifier of selecting for use, input impedance＞10
13Ω, standard capacitance is set to circumscribed, and is connected with instrument amplifier by four line access methods, and described four line access methods are capacitance terminal I
HAs the external voltage signal input end, with capacitance terminal V
HGuide to the instrument amplifier positive input, capacitance terminal V
LConnect the instrument amplifier reverse input end, capacitance terminal I
LAs signal output part.Standard capacitance is preferably four ends to standard capacitance, in the present embodiment, standard capacitance adopts the 16380 serial electric capacity of Agilent, instrument amplifier is a kind of closed loop gain unit with difference input and the single-ended output of relative reference end, it can amplify the difference of two applied signal voltages and suppress any signal to two input end common modes, here instrument amplifier is elected three amplifier differential amplifiers as, comprise two prebuffers and the unity gain differential amplifier that links to each other with prebuffer, two prebuffers provide unity gain for input difference voltage, the unity gain differential amplifier provides single ended output voltage over the ground, connect feedback resistance between two prebuffers, input bias current＜the 1pA of prebuffer, input impedance＞10
13Ω; The gain error of unity gain differential amplifier＜0.01%; Input offset voltage＜50uV.We have selected for use the electrometer level operational amplifier OPA128LM of BB company production as the input buffering level, select for use accurate unity gain differential amplifier INA105BM to build the instrument amplifier circuit as output stage, electrometer level operational amplifier 0PA128LM has extremely low bias current, offset voltage drift as prebuffer; High input impedance, open-loop gain and frequency response, its typical technology index is: input bias current: 40fA; Input offset current: 30fA; Input offset voltage: 140uV; Input offset voltage drift: 5uV/ ℃; Input impedance: greater than 10
13Ω; Open-loop gain: 128dB; Frequency response: 1MHz; Output resistance: 100 Ω; Supply voltage: ± 15V, unity gain differential amplifier INA105BM chip integration becomes 4 25k Ω pin-point accuracies, temperature to float consistent laser-induced thermal etching resistance, guaranteed gain and higher common-mode rejection ratio accurately, the typical technology index is: gain error: 0.005%; Nonlinearity erron: 0.0002%; Output impedance: 0.01 Ω;-3dB cutoff frequency: 1MHz; Input offset voltage: 50uV; The input offset voltage drift: 5uV/ ℃, the CMRR that INA105BM is very high, the good linearity, offset voltage drift and frequency characteristic, the environmental baseline temperature is 20 ℃ ± 2 ℃ during calibrating, humidity is 30%RH～70%RH.
Fig. 2 is the circuit diagram of the instrument amplifier of alternating voltage current converter of the present invention.U wherein
4, U
5Be prebuffer, for input difference voltage provides unity gain; U
8Be the unity gain differential amplifier, single ended output voltage over the ground is provided; The V of the 16380 serial electric capacity of Agilent
HAnd V
LEnd connects the input end of two prebuffer OPA128LM.Also be provided with the equivalent potential screen circuit, this equipotential screened circuit is that two prebuffers are connected with a voltage follower separately, the output terminal of prebuffer is drawn the current potential (buffer stage is a unity gain) that equates with the difference input, and be connected respectively to the voltage follower input end, the output of described voltage follower connects the intershield layer of the input signal cable of prebuffer, input bias current＜the 1pA of voltage follower, input impedance＞10
13Ω.Among Fig. 2, U
1, U
2Voltage follower for OPA128LM constitutes provides equivalent potential screen voltage.Use equal potential screening technique, can avoid the generation of leaking, OPA128LM that extremely low offset voltage and drift, high input impedance and good frequency characteristic are arranged, very little to the influence of instrument amplifier buffer stage output, can ignore.
Alternating voltage current converter standard capacitance when making is set to circumscribed, the little current amplitude of the interchange that can obtain as required, frequency and formula I
n=2 π fC
nU
nDetermine required standard capacitance value, thereby change the standard capacitance of different ranges, the shell of alternating voltage current converter of the present invention adopts the pure iron material to make the housing of a closure, the 16380 serial electric capacity shells of Agilent can be iron shields, and standard capacitance is connected by concentric cable with the alternating voltage current converter circuit, and two parts are when work like this, form a complete shield, effectively reduced the disturbing effect of external electromagnetic field; Standard capacitance is connected with instrument amplifier by high insulation shielding cable, and high insulation shielding cable can be selected three coaxial teflon cables, adopts the high insulated cable of three coaxial teflon as the connecting line material, and its insulation resistance can reach 10
14Ω, the middle layer can be used as the equivalent potential screen layer, and the protection internal layer circuit reduces leakage current; Select the connector and the changeover plug of the high insulation of teflon for use, can also reduce leakage; Standard capacitance four line access methods connect, and take out standard capacitance two ends potential difference (PD) at potential end, have minimized the influence of lead-in wire interchange parameter.
Owing to used triaxial cable and connector Shielding Design, equal potential screening technique, the differential amplifying technique of three amplifiers etc., effectively reduced external disturbance and noise, guaranteed the accuracy and the stability of alternating voltage current converter.
What standard capacitance adopted is 16380 serial electric capacity of Agilent company, and preferably, a year relative stability index is better than 3 * 10
-4, and by China metering universities and colleges standard, the uncertainty after the metering universities and colleges standard is 3 * 10
-5(k=2), and adopt housing to connect cold end equivalent potential screen voltage method,, eliminated this error source for stray capacitance provides bypass channel; The prebuffer OPA128LM input offset voltage of instrument amplifier is about 140uV, offset current is 30fA, bias current is 40fA, the offset voltage drift is for 5uV/ ℃, these amounts of influence are compound in circuit to be the common mode interference amount, approaching two amplifiers of our selectivity characteristic are eliminated this part common mode interference as input stage through differential amplifier; The input impedance of instrument amplifier differential input end is about 10
15Ω is 1.59 * 10 and different frequency, capacitance and voltage make up pairing maximum capacitor impedance
9, the input impedance of instrument amplifier is higher than 10 of measured output impedance
5Times, so the error that instrument amplifier input impedance is introduced can be ignored; Can adopt multi-functional standard source 5720A that input and output voltage, the frequency of instrument amplifier are calibrated, adopt the method for pointwise calibration input and output voltage, therefore the nonlinearity erron and the voltage gain error of instrument amplifier can be considered, adopt the method for pointwise calibration input and output frequency, therefore the frequency error of instrument amplifier can be considered, has so just eliminated self error of instrument amplifier.
Fig. 3 is the theory diagram that the present invention examines and determine the device that exchanges little reometer.This device has adopted alternating voltage current converter provided by the invention, the present invention examines and determine the device that exchanges little reometer and comprises standard voltage source, alternating voltage current converter, frequency meter and AC digital voltmeter, the standard electric alternating current potential source is on output voltage point, and the relative stability index should be better than 3 * 10 in 24 hours
-4, the forward end of described standard voltage source inserts capacitance terminal I
H, the backward end of standard voltage source and capacitance terminal I
LInsert the I of the little reometer of tested interchange respectively
LEnd and I
HEnd, described digital voltmeter links to each other with the output of instrument amplifier respectively with frequency meter.Here standard voltage source is selected 5720A, and AC digital voltmeter is selected 8508A, and on measured electrical voltage point, year stability should be better than 1.5 * 10 relatively
-4, frequency meter is selected 53131A, and the 5720A output AC voltage is carried in the two ends of 16380 series standard electric capacity, produces alternating current, and the electric current that then flows through electric capacity equals to flow through the electric current of tested table.Standard capacitance is less at capability value, its equivalent output impedance was very big when frequency of operation was low, if adopt AC digital voltmeter 8508A directly to measure the method for its terminal voltage (input impedance mostly is G Ω level), easily cause AC digital voltmeter internal resistance shunting, form big measuring error, and the output offset current when AC digital voltmeter is measured alternating voltage is bigger, become the noise current of circuit, therefore adopted instrument amplifying circuit with T Ω level input resistance and pA level bias current, come measurement standard electric capacity both end voltage, use formula I
n=2 π fC
nU
nThe electric current that standard capacitance is flow through in calculating is examined and determine tested little reometer as standard value.Thereby it is minimum that measuring equipment is reduced to the influence of electric current in the circuit, got rid of standard capacitance simultaneously to impedance influences that goes between between standard voltage source and leakage contribution.
For fear of or alleviate leakage current and bleeder resistance exchange little reometer to calibrating influence to greatest extent, taked the equivalent potential screen measure, specifically, " Guard-" and " Guard+ " end with instrument amplifier is equivalent potential screen output terminal, the standard capacitance V of corresponding input respectively
LAnd V
HTerminal potential; " Guard+ " output is connected to the connection standard capacitance and instrument amplifier is imported the middle layer conductor of the triaxial cable of end in the same way, reduces the leakage in high output impedance source; " Guard-" output is connected to the middle layer conductor of the triaxial cable that connects standard capacitance and instrument amplifier input backward end and the outer shield shell of standard capacitance, when reduce leaking also the stray capacitance for standard capacitance inside bypass channel is provided, got rid of the influence of stray capacitance (parallel connection) to measuring.
The little reometer of tested interchange, instrument amplifier is connected computing machine by gpib interface respectively with frequency meter, computing machine calculates and demonstrates the alternating current flow valuve by the transitive relation of the conversion of the electric current and voltage between alternating voltage and the alternating current, finish control by computer program control, calculate and automatic Verification, as use the Labview7.0 establishment to exchange little electric current automatic test program, can select the range and the measurement point of tested little reometer, according to the electric current and voltage conversion formula of determining, can calculate automatically and exchange little current value, and show test data with form dynamically, operation indicating is arranged in the measuring process, as point out and change standard capacitance and wiring, after test is finished, test result can be kept in the e-file, and can go out automatic generation test report as required, for example can write among the EXCEL automatically and file, finish exchanging the calibrating of little reometer, save the time of calculating and data recording, improved surveying work efficient, saved human cost.Wherein, be that the computing formula of electric current is I by voltage transitions
n=2 π fC
nU
n, C wherein
nBe the capacitance of standard capacitance, f is an AC current frequency, U
nBe the effective value of alternating voltage, I
nEffective value for alternating current.
A kind of method that exchanges little reometer of examining and determine comprises the steps:
A, standard voltage source convert alternating current to by above-mentioned alternating voltage current converter, and described alternating current inputs to the little reometer of tested interchange;
B, the output of the instrument amplifier in the alternating voltage current converter is connected AC digital voltmeter and frequency meter respectively, and the alternating voltage by AC digital voltmeter measurement standard electric capacity two ends, AC current frequency measured by frequency meter;
C, the little reometer of tested interchange, instrument amplifier are connected computing machine by gpib interface respectively with frequency meter, and described computing machine calculates and demonstrate the alternating current flow valuve by the transitive relation of the conversion of the electric current and voltage between alternating voltage and the alternating current.
The alternating voltage current converter is applied to standard voltage source on the standard capacitance, then with the voltage amplification at standard capacitance two ends and deliver to the interchange standard voltmeter, calibrate the little reometer of interchange by calculating standard current value, to exchange little electric current and be traceable on electric capacity, alternating voltage and the frequency, solve the problem of tracing to the source.
Fig. 4 is the test data table that the present invention examines and determine the device that exchanges little reometer, has measured the data of digital multimeter 8508A.
Through evaluation, can obtain the relative expanded uncertainty table that the present invention examines and determine the device that exchanges little reometer, as shown in Figure 5, uncertainty k=2 wherein, U
rBe relative expanded uncertainty.
Above-described example only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (9)
1. an alternating voltage current converter is characterized in that comprising standard capacitance, instrument amplifier, and described standard capacitance is set to circumscribed, and described standard capacitance is connected with instrument amplifier by four line access methods, and described four line access methods are capacitance terminal I
HAs the external voltage signal input end, with capacitance terminal V
HGuide to the instrument amplifier positive input, capacitance terminal V
LConnect the instrument amplifier reverse input end, capacitance terminal I
LAs signal output part, described instrument amplifier is three amplifier differential amplifiers, described three amplifier differential amplifiers comprise two prebuffers and the unity gain differential amplifier that links to each other with prebuffer, the input bias current＜1pA of described instrument amplifier, input impedance＞10
13Ω.
2. a kind of alternating voltage current converter according to claim 1 is characterized in that described standard capacitance is that four ends are to standard capacitance.
3. a kind of alternating voltage current converter according to claim 1 and 2, it is characterized in that two prebuffers provide unity gain for input difference voltage, the unity gain differential amplifier provides single ended output voltage over the ground, connect feedback resistance between described two prebuffers, input bias current＜the 1pA of described prebuffer, input impedance＞10
13Ω; The gain error of described unity gain differential amplifier＜0.01%; Input offset voltage＜50uV; The V of described standard capacitance
HAnd V
LEnd connects the input end of two prebuffers respectively.
4. a kind of alternating voltage current converter according to claim 3 is characterized in that described standard capacitance shell makes shield, and is connected with instrument amplifier by high insulation shielding cable.
5. a kind of alternating voltage current converter according to claim 4 is characterized in that described high insulation shielding cable is three coaxial teflon cables.
6. a kind of alternating voltage current converter according to claim 5, it is characterized in that also being provided with the equivalent potential screen circuit, described equivalent potential screen circuit is that two prebuffers are connected with a voltage follower separately, the output terminal of prebuffer is drawn the current potential that equates with the difference input of three amplifier differential amplifiers, and be connected respectively to the voltage follower input end, the output of described voltage follower connects the intershield layer of the input signal cable of prebuffer, input bias current＜the 1pA of described voltage follower, input impedance＞10
13Ω.
7. adopt a kind of device that exchanges little reometer of examining and determine of one of claim 1 to 6 described alternating voltage current converter, it is characterized in that comprising standard voltage source, alternating voltage current converter, frequency meter and AC digital voltmeter, the forward end of described standard voltage source inserts capacitance terminal I
H, the backward end of standard voltage source and capacitance terminal I
LInsert the I of the little reometer of tested interchange respectively
LEnd and I
HEnd, described digital voltmeter links to each other with the output of instrument amplifier respectively with frequency meter.
8. calibrating according to claim 7 exchanges the device of little reometer, it is characterized in that the little reometer of described tested interchange, instrument amplifier are connected computing machine by gpib interface respectively with frequency meter, described computing machine calculates and demonstrates the alternating current flow valuve by the transitive relation of the conversion of the electric current and voltage between alternating voltage and the alternating current.
9. adopt a kind of method that exchanges little reometer of examining and determine of one of claim 1 to 6 described alternating voltage current converter, it is characterized in that comprising the steps:
A, standard voltage source convert alternating current to by described alternating voltage current converter, and described alternating current inputs to the little reometer of tested interchange;
B, the output of the instrument amplifier in the alternating voltage current converter is connected AC digital voltmeter and frequency meter respectively, and the alternating voltage by AC digital voltmeter measurement standard electric capacity two ends, AC current frequency measured by frequency meter;
C, the little reometer of tested interchange, instrument amplifier are connected computing machine by gpib interface respectively with frequency meter, and described computing machine calculates and demonstrate the alternating current flow valuve by the transitive relation of the conversion of the electric current and voltage between alternating voltage and the alternating current.
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| CN2008101126567A CN101285852B (en) | 2008-05-26 | 2008-05-26 | Alternating current voltage electric current converter and device and method for testing alternating-current small ammeter |
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|---|---|---|---|
| CN2008101126567A CN101285852B (en) | 2008-05-26 | 2008-05-26 | Alternating current voltage electric current converter and device and method for testing alternating-current small ammeter |
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| CN101980041A (en) * | 2010-10-25 | 2011-02-23 | 南车戚墅堰机车有限公司 | Intelligent calibration system for instrument |
| CN102353857B (en) * | 2011-07-05 | 2013-09-18 | 苏州索拉科技有限公司 | Electric signal detection system |
| CN107015060B (en) * | 2017-03-20 | 2019-04-23 | 西安交通大学 | Method and system for measuring alternating current resistance of power transmission conductor |
| CN109813973B (en) * | 2018-12-18 | 2021-02-19 | 兰州空间技术物理研究所 | Bias current calibration method for space electric field detector |
| CN109541513B (en) * | 2018-12-25 | 2022-02-08 | 北京东方计量测试研究所 | Alternating current micro-current tracing device and method |
| CN110658374A (en) * | 2019-11-14 | 2020-01-07 | 河北申科电子股份有限公司 | Current transformer with wide frequency, wide measurement and anti-magnetic interference capability |
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