CN108107260A - Wide-range high-precision micro current system and method - Google Patents
Wide-range high-precision micro current system and method Download PDFInfo
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- CN108107260A CN108107260A CN201711158953.0A CN201711158953A CN108107260A CN 108107260 A CN108107260 A CN 108107260A CN 201711158953 A CN201711158953 A CN 201711158953A CN 108107260 A CN108107260 A CN 108107260A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
Abstract
The present invention relates to wide-range high-precision micro current system and methods.The system includes multiple root signal converter, analog to digital conversion circuit and microprocessor circuit, wherein, the multiple root signal converter includes logarithmic transformation circuit, adder, exponential transform circuit, the logarithmic transformation circuit receives micro current signal to be measured and reference current signal, logarithmic transformation is carried out respectively exports two voltage signals to the adder, the adder is sent to the exponential transform circuit after summing to the voltage signal, the exponential transform circuit receives described and row index conversion of going forward side by side, analog voltage signal is exported to analog-digital conversion circuit as described；Analog-digital conversion circuit as described, which receives the analog voltage signal and changes into digital signal, is sent to the microprocessor circuit；The microprocessor circuit receives the digital signal, carries out repeatedly the value that square computing reduces the current signal to be measured, completes current measurement.The present invention has in gamut scope compared with high measurement accuracy.
Description
Technical field
The present invention relates to micro current system and method, more particularly to wide-range high-precision micro current system and
Method can be applied to the detection field of all kinds of instrument and equipment ion currents, photoelectric current and other weak currents.
Background technology
In apparatus measures, it is often necessary to detect various current signals, such as mass spectrometer ionization source pound come from
Sub- fragment electric current, gas-chromatography hydrogen flameionization electric current, total amount ion stream that ion gauge changes into vacuum degree and
Photoelectric current that faint optical signal generates etc., these current signals are often differed from " fA " grade to " mA " grade, do not require nothing more than pole
Weak current ability also requires that enough Measurement Resolutions can be obtained in wider measurement range, therefore wide scope
Weak current measuring system becomes a quite crucial core technology in instrument development.
Prior art one：As shown in Figure 1, the technology of existing wide scope weak current is used with negative-feedback more
Operational amplification circuit carries out I-V (current-voltage) and converts, and is realized in a manner that high resistant switches expanded range.In which
J1-J4 is relay, and per group relay, cooperation sampling feedback resistance forms corresponding range, by relay switching come adjustment amount
Journey.
When this programme measures weak current, measurement lower limit depends on the size of feedback high resistant, when measuring fA grades of electric currents,
The resistance value of this feedback high resistant will be not less than 10G ohm, and feedback high resistant is bigger, the easier self-oscillation of circuit, in practical applications
Often on high resistant a high insulativity in parallel thin-film capacitor, constitute the bandwidth that a RC time constant limits measurement,
The measuring speed that electric current is so also led to while circuit stability is increased is restricted；In addition, this I-V translation circuits
Noise, essentially from operational amplifier noise and feedback high resistant noise, modern electrometer operational amplifier A D549
(or OPA129 etc.) noise is very small, and when high resistant is more than 1G ohm, the noise of amplifier can be far smaller than high resistant
Johnson noise is also referred to as thermal noise, and resistance value is higher, resistance stability is required stringenter.Also have using T-shaped resistance net
Network mode, as shown in Fig. 2, achieving the purpose that reduce high resistant resistance value in the case of not changing gain.Actually this is a kind of simplification
Second amplifying circuit, micro-current flows through the voltage signal that first order high resistant is amplified, this voltage signal is by subsequent partial pressure
Network continues to amplify, and the noise of first order high resistant also can be equally amplified at this time.
The Johnson noise is also referred to as thermal noise
Wherein k is Boltzmann constant (1.38 × 10^-23J/K), and T is temperature, and Δ f is bandwidth, and R is resistance value.
By Johnson noise formula, the effect of two level measurement by magnification is good not as good as the effect of single-stage measurement by magnification.It is high
The resistance value of resistance is bigger, and slightly larger measurement electric current easily makes amplifier export saturation, influences to measure the upper limit of electric current, to extend measurement
Range only have the size for switching feedback high resistant to realize.
During band range switching high resistant negative-feedback measurement method, electricity can be greatly reduced in high resistant requirement working environment drying, humidity
Hinder table resistivity.Component number needed for this measurement method is more, it is necessary to relay is controlled to carry out switching range, complicated,
Volume is big, and precision is poor, and reliability is low and the response time is slow.Particularly in the continuous measurement process of analytical instrument, small-signal
It tends not to take into account with big signal or weak-signal measurement sensitivity is inadequate or saturation state occurs in big signal measurement.
Prior art two：The measurement range of electric current is extended using the method for log-compressed I-V conversion circuits.Pass through
Logarithmic converter makes input/output signal into logarithmic relationship, so as to fulfill the non-linear compression of signal.This kind of Signal Compression mode
It has been widely used in fields such as communication, radar, Photoelectric Detection and space flight.
Log-compressed I-V translation circuit detection modes solve the problems, such as Larger Dynamic scope, but logarithmic transformation circuit has one
The defects of a intrinsic, i.e. output signal voltage, are related to temperature, it is necessary to carry out temperature-compensating well.General method is to use
Make on the same chip to pipe come PN junction reverse saturation current Is in offsetting, compensate thermal voltage VT with thermistor, but
Thermistor is difficult in the most appropriate compensation of a wide range of interior work, and apolegamy trouble, also can even with high-accuracy integrated circuit
It is influenced be subject to these factors.In addition by the way of log-compressed, small signal variation is excessively fierce, and when big signal is compressed non-
Often severe, in whole measurement ranges being particularly big signal section measurement hardly results in more number of significant digit.
The shortcomings that due to the prior art, the present invention intend proposing wide-range high-precision micro current system and method.
The content of the invention
It is an object of the invention to provide wide-range high-precision micro current system and method, to fA to uA grades (10-14A
~10-5A) current signal carries out multiple root non-linear compression, and improving electric current while quickly detection wide scope electric current surveys
Accuracy of measurement can be applied to the detection field of all kinds of instrument and equipment ion currents, photoelectric current and other weak currents.
The present invention provides a kind of wide-range high-precision micro current system, and the system is converted comprising multiple root signal
Device, analog to digital conversion circuit and microprocessor circuit, wherein,
The multiple root signal converter includes logarithmic transformation circuit, adder, exponential transform circuit, and the logarithm becomes
It changes circuit and receives micro current signal to be measured and reference current signal, carry out logarithmic transformation respectively and obtain two voltage signals and be sent to
The adder, the adder are sent to the exponential transform circuit after summing to described two voltage signals, the index becomes
Change described in circuit reception and row index conversion of going forward side by side, one analog voltage signal of output to analog-digital conversion circuit as described；
The analog voltage signal that the multiple root signal converter comes out is converted by analog-digital conversion circuit as described
Digital signal；
The microprocessor circuit gathers the digital signal, carries out repeatedly square calculation process by software program, finally
The value of the current signal to be measured is restored, completes current measurement.
Further, the scope of the micro-current to be measured is 10-14A~10-5A。
Further, the multiple root signal converter uses multiple root non-linear compression mode, and described is multiple
Root includes square root or 2 times or more roots.
Further, the analog voltage signal of the multiple root signal converter output is 0~10V.
Further, the multiple root signal converter is shielded using the metal shielding box of ground connection.
Further, the multiple root signal converter signal input line is the double layer screen line with graphite linings.
Further, the signal input part of the multiple root signal converter is in a manner that porcelain substrate puts in a skylight, letter
Number line is printed directly on circuit board.
Further, the logarithmic transformation circuit includes the operational amplifier being electrically connected, transistor, resistance, capacitance, institute
Operational amplifier is stated as AD549 or OPA129, the transistor is for triode to pipe MAT01 or field-effect to pipe AD830.
It is a further object to provide a kind of micro- using wide-range high-precision micro current system progress
The method of current measurement, comprises the following steps：
Step S1, the input terminal of the multiple root signal converter receive the micro current signal to be measured, and to its into
The multiple root signal conversion of row, output analog voltage signal are sent to analog-digital conversion circuit as described；
The analog voltage signal is converted into digital signal by step S2, analog-digital conversion circuit as described, is sent to micro- place
Manage device circuit；
Step S3, the microprocessor circuit receive the digital signal, are carried out repeatedly at square computing by software program
Reason finally restores the value of the current signal to be measured, completes current measurement.
Wherein, the method for multiple root signal conversion comprises the following steps described in step S1：
The multiple root signal converter receives the micro current signal to be measured and the reference current signal, and to two
A current signal carries out logarithmic transformation respectively, and the voltage signal for obtaining two and the current signal into logarithmic relationship is sent to
The adder；
The adder after two voltage signal summations to being sent to the exponential transform circuit；
The exponential transform circuit after the exponential transform with progress to obtaining analog voltage signal, the analog voltage
Signal is the multiple root signal of the electric current to be measured.
Present invention obtains obviously benefits：
The present invention can measure atomic weak current without the high resistant of very big resistance value；
The current measurement of wide scope can be realized without range switching；
Since the influence of no RC time constants can also be measured quickly；
The circuit part perfection of Signal Compression eliminates the parameter that temperature influences in logafier；
There is larger gain in small-signal, and gain reduces when larger signal, has in the range of whole ranges
Higher measurement accuracy；
ADL5304 is the representative of high-level accurate logarithmic converter integrated circuit, at entire 200dB (1pA to 10mA)
There is quick response and low noise, by the input-output signal curve for comparing ADL5304 and present example in measurement range
Such as Fig. 7, it is possible to find, when whole ranges have the requirement compared with high measurement accuracy, the present invention's is with the obvious advantage.
Description of the drawings
Fig. 1：Conventional negative feedback operational amplification circuit I-V converters.
Fig. 2：Traditional T-shaped resistor network I-V converters.
Fig. 3：Present system block diagram.
Fig. 4：Logafier basic circuit.
Fig. 5：The multiple root signal converter basic model circuit of 1 square root Signal Compression mode of embodiment.
Fig. 6：The 2 multiple root signal converter improved circuit of square root Signal Compression mode of embodiment.
Fig. 7：Present example and the input-output signal curve of ADL5304 comparisons.
Specific embodiment
With reference to the accompanying drawings and embodiments, the specific embodiment of the present invention is described in more details, so as to energy
The advantages of enough more fully understanding the solution of the present invention and its various aspects.However, specific embodiments described below and reality
Example is applied to be for illustrative purposes only rather than limitation of the present invention.
The present invention relates to wide-range high-precision micro current system and method, as shown in figure 3, Fig. 3 is present system
Block diagram, the system include multiple root signal converter 1, analog to digital conversion circuit 2 and microprocessor circuit 3.The multiple side
Root signal converter 1 is a kind of I-V signal converters, and I-V signal converters are current-voltage signal converters.The modulus
Conversion circuit 2 is A/D analog to digital conversion circuits, and A/D is the abbreviation of analog/digital (Analog/Digital).
The system can realize 10-14A~10-5The quick detection of A wide-ranges weak current high-precision.The multiple root letter
Number converter 1 includes logarithmic transformation circuit 11, adder 12, exponential transform circuit 13.The reception of logarithmic transformation circuit 11 is treated
Micrometer current signal and reference current signal obtain two voltage signals feeding additions after carrying out logarithmic transformation to it respectively
Device 12；The adder 12 is sent to the exponential transform circuit 13, the exponential transform after summing to described two voltage signals
Circuit 13 receives described and and exports analog voltage signal after carrying out exponential transform to it；Analog-digital conversion circuit as described 2 is by institute
It states the analog voltage signal that multiple root signal converter 1 comes out and is converted into digital signal；The microprocessor circuit 3 is adopted
Collect the digital signal, square calculation process carried out repeatedly by software program, finally restores the value of the current signal to be measured,
Complete current measurement.
The method that micro current is carried out using the wide-range high-precision micro current system, is comprised the following steps：
Step S1, the input terminal of the multiple root signal converter 1 receive the micro current signal to be measured, and to its into
The multiple root signal conversion of row, output analog voltage signal are sent to analog-digital conversion circuit as described 2；
The analog voltage signal is converted into digital signal by step S2, analog-digital conversion circuit as described 2, is sent to micro- place
Manage device circuit 3；
Step S3, the microprocessor circuit 3 receive the digital signal, are carried out repeatedly at square computing by software program
Reason finally restores the value of the current signal to be measured, completes current measurement.
Wherein, the method for multiple root signal conversion comprises the following steps described in step S1：
The logarithmic transformation circuit 11 receives the micro current signal to be measured and the reference current signal, and to two institutes
State current signal and carry out logarithmic transformation respectively, obtain two and the current signal into logarithmic relationship voltage signal be sent to it is described
Adder 12；
The adder 12 is sent to the exponential transform circuit 13 after summing to described two voltage signals；
The exponential transform circuit 13 is to obtaining analog voltage signal, the simulation electricity after the exponential transform with progress
Pressure signal is the multiple root signal of the electric current to be measured.
See Fig. 3, when micro current signal measures, as far as possible reduce external environment in piezoelectric effect, pyroelectric effect and
Electromagnetic interference caused by triboelectrification effect etc., the multiple root signal converter 1 is using the metal shielding box screen being grounded
It covers, reduces interference of the outside noise signal to measuring circuit.
Since common PCB printed circuit board (PCB) impedances are inadequate, interference of the leakage current to input signal, generally exists in order to prevent
Signal input part is maked somebody a mere figurehead with the polytetrafluoroethylene (PTFE) pillar of high insulativity, and structure is more complicated, and volume is relatively large, if using
OPA129 patch integrated circuits, pin can not also make somebody a mere figurehead, further, since signal wire is hanging, vibrations can cause signal and ground wire it
Between parasitic capacitor variations, influence measurement accuracy.The present invention is in a manner that ceramic substrate opens " skylight ", PCB printed circuit board (PCB)s
Ceramic substrate material is selected, signal wire is printed directly on circuit board, and increases bottom solder mask in stimulus part, only
Wiring is without upper green oil.Since ceramic substrate has good electrical insulation performance and higher mechanical strength, big in high epidemic disaster
Under the conditions of performance have good performance, be so greatly improved stability in micro current.
Multiple 1 signal input line of root signal converter is the double layer screen line with graphite linings, and signal input line needs
It fixes.
The multiple root signal converter 1 uses multiple root non-linear compression mode, and the electric current to be measured of input is believed
Analog voltage signal number is transformed to, the output analog voltage signal is the multiple root letter of the input current signal to be measured
Number, the multiple root includes square root or 2 times or more roots, and practical is using square root or cubic root compression side
Formula.
The micro current signal to be measured that the multiple root signal converter 1 receives is smaller, and signal gain amplifier is bigger, can be with
Ensure weak-signal measurement precision；And micro current signal to be measured is bigger, signal gain is smaller, and big signal can be compressed, and carries
The range of high measurement.
The logarithmic transformation circuit 11 includes the operational amplifier being electrically connected, transistor, resistance, capacitance.The computing
Amplifier will select ultralow input bias current, low noise electrometer operational amplifier, such as AD549 or the TI public affairs of ADI companies
The OPA129 of department.The selection of the transistor is also very crucial, and the rain supply of common transistor feedback element is limited in low electricity
The response under scope is flowed, therefore to select the differential pair tube of low noise, high-gain, low current leakage, makes it in input small-signal
When, Logarithm conversion still has a higher precision, such as ADI companies MAT01 triodes to pipe.Also can be imitated with the field of a high impedance
Transistor is answered to make feedback element, it is easy to the upper current limit of logafier can be made to expand to below 1pA, usually imitate a field
Should pipe drain electrode be interconnected with source electrode together with when, just constitute the low diode of leakage current, for example select the field-effect of pairing
Pipe AD830 (American Microsemiconductor companies) etc. just has fabulous temperature stability and ultralow electric leakage
Stream.Requiring pipe for reference current measurement part can be slightly lower, MAT12 of ADI companies etc. can be selected, remaining operational amplifier is then
Select general low-noise accurate amplifier TL072, AD648 etc..
The basic circuit of the multiple root signal converter 1 is log amp circuit, as shown in figure 4, Fig. 4 is logarithm
The basic circuit of amplifier.Transistor collector electric current Ic and Ube can meet exponential relationship in very wide scope, i.e.,
In formula：Ic-collector current；
Is-reversed the drain saturation current of transistor emission knot；
T-absolute temperature；
K-Boltzmann constant；
Q-electronic charge；
Ube-transmitting junction voltage.
WhenWhen, thenBoth sides take natural logrithm
Wherein thermal voltageFor constant, by Ube ≈-V0,Substitution formula (2)
Therefore input voltage Vi and output voltage Vo is into logarithmic relationship.
Thermal voltage U is understood by logafier operation principleTWith the reversed drain saturation current Is of transistor emission knot be with
A related amount of temperature, this just determines that the operational precision of this logafier changes with temperature.Therefore, actually should
Temperature-compensating measure must be taken in.And the circuit perfection of the multiple root signal converter 1 of the present invention eliminates logarithm and puts
Parameter U in big deviceTIt is influenced with the temperature of Is.
Analog-digital conversion circuit as described 2 is mainly comprising integrated modulus conversion chip and reference voltage source.Modulus conversion chip selects
With 24 ultra-low noise chips, such as ADS1255 or AD7176-2.Wherein ADS1255 is buffered by analog multichannel switch, input
Device, programmable gain amplifier, fourth-order modulator of Figure add a programmable digital-filter composition again.And AD7176-2 is integrated with friendship
Crunode multiplexer, three kinds of main digital filters and modulator, this kind of modulus conversion chip cooperation ultraprecise ADR42x
Series of reference voltage source can reach 22 number of significant digit precision when low speed is converted, therefore in the current measurement upper limit (10uA
Grade) part its Measurement Resolution still can reach 10pA or so.3 lines or 4 line serial digital interfaces in modulus conversion chip will
Digital signal is sent to the microprocessor circuit 3.
The microprocessor circuit 3 include microcontroller chip and peripheral interface circuit, communicating circuit, power circuit with
And 32 embeded processors, such as STM32 series can be selected in the parts such as external clock reference, microcontroller chip.Microcontroller
Chip receives the digital signal by serial digital interface.
Embodiment 1
The present embodiment 1 is a kind of wide-range high-precision micro current system, as shown in figure 3, the system includes repeatedly
Root signal converter 1, analog to digital conversion circuit 2 and microprocessor circuit 3, the multiple root signal converter 1 include logarithm
Computing circuit 11, adder 12, exponent arithmetic circuit 13.Wherein, the multiple root signal converter 1 employs square root letter
Number basic compress mode, as shown in figure 5, Fig. 5 is the multiple root signal converter basic model circuit of square root Signal Compression mode.
See that Fig. 5, operational amplifier U1 and triode Q1A, operational amplifier U2B and triode Q2B form logarithm operation
Circuit 11, output voltage are：
See that Fig. 5, operational amplifier U2A form adder 12, if resistance R4=R5=R7, adder output voltage
For：
See Fig. 5, operational amplifier U3A and triode Q1B, Q2A Composition index computing circuit 13, the 2 of operational amplifier U3A
Foot virtual earth, then voltage Vo3 voltages are exactly that the sum of transmitting junction voltage of triode Q1B, Q2A is：
It is analyzed from above formula：
Iin·Iref=Iout·Iout
Therefore, final signal output voltage is：
The analog to digital conversion circuit 2 is mainly comprising integrated modulus conversion chip ADS1255 and ADR42x series of reference electricity
Potential source.The analog voltage signal Vo that the multiple root signal converter 1 comes out is converted into digital signal, the number is believed
Number it is sent to the microprocessor circuit 3.
The microprocessor circuit 3 receives the digital signal, carries out repeatedly square calculation process by software program, finally
The sizes values of original signal are restored, calculate Iin, complete current measurement.
Embodiment 2
The present embodiment 2 is a kind of wide-range high-precision micro current system, as shown in figure 3, the system includes repeatedly
Root signal converter 1, analog to digital conversion circuit 2 and microprocessor circuit 3, the multiple root signal converter 1 include logarithm
Computing circuit 11, adder 12, exponent arithmetic circuit 13.Wherein, the multiple root signal converter 1 employs square root letter
Number modified compress mode, as shown in fig. 6, Fig. 6 is the multiple root signal converter improved electric of square root Signal Compression mode
Road.
See Fig. 6, the ingenious operational amplifier U1 using in the logarithmic operational circuit for wherein measuring current segment is as addition
Device 12 simplifies circuit, and triode Q1A collectors connect end of oppisite phase 2, base stage connects in-phase end 3, due to empty short with end of oppisite phase 2, so
Triode Q1A and operational amplifier U1 forms logarithmic operational circuit 11；The logarithmic operational circuit of another reference current part is defeated
Go out to terminate the in-phase end 3 of this U1 operational amplifier, therefore the output voltage Vo2 of this logarithmic operational circuit 11 is superimposed upon measurement
In the logarithmic operational circuit output voltage of current segment, concrete analysis is similar to square root Signal Compression mode basic model, therefore,
Obtaining final signal output voltage is：
It follows that the square root of circuit output voltage and electric current is linear and temperature independent.Actual circuit
Parameter selection Iref=100uA, R5=330k Ω, therefore output voltage calculated value see the table below.
This multiple root signal converter improved circuit meets measurement range from 10fA to 10uA, and dynamic range is more than
109.Experiment confirms, 10 can be realized using the circuit-14A~10-5A wide-range low current signals are converted into voltage signal
Function.
The analog voltage signal Vo that the analog to digital conversion circuit 2 comes out the multiple root signal converter 1 is converted
Into digital signal, when analog to digital conversion circuit 2 selects 24 modulus conversion chip such as ADS1255 or AD7176-2, in low speed
Reach 22 number of significant digit precision during conversion, thus it is still reachable in (10uA grades) its Measurement Resolution of part of the current measurement upper limit
Arrive 10pA or so.
The microprocessor circuit 3 gathers the digital signal, carries out repeatedly square calculation process by software program, finally
The sizes values of original signal are restored, calculate Iin, complete current measurement.
Finally it should be noted that：The above embodiment is merely an example for clearly illustrating the present invention, and is not pair
The restriction of embodiment.For making other variations or changes in different ways on the basis of the above description, still in this hair
Among bright protection domain.
Claims (10)
1. a kind of wide-range high-precision micro current system, the system comprises multiple root signal converter, analog-to-digital conversions
Circuit and microprocessor circuit, wherein,
The multiple root signal converter includes logarithmic transformation circuit, adder, exponential transform circuit, the logarithmic transformation electricity
Road receives micro current signal to be measured and reference current signal, carries out logarithmic transformation respectively and obtains two voltage signals and be sent to described
Adder, the adder are sent to the exponential transform circuit, the exponential transform electricity after summing to described two voltage signals
Road reception is described to be converted with row index of going forward side by side, output analog voltage signal to analog-digital conversion circuit as described；
Analog-digital conversion circuit as described, which receives the analog voltage signal and is converted into digital signal, is sent to the microprocessor circuit；
The microprocessor circuit receives the digital signal, carries out repeatedly square calculation process, finally restores the electricity to be measured
The value of signal is flowed, completes current measurement.
2. system according to claim 1, which is characterized in that the scope of the micro-current to be measured is 10-14A~10-5A。
3. system according to claim 1, which is characterized in that the multiple root signal converter is non-using multiple root
Linear compression mode, the multiple root include square root or 2 times or more roots.
4. system according to claim 1, which is characterized in that the analog voltage of the multiple root signal converter output
Signal is 0~10V.
5. system according to claim 1, which is characterized in that the multiple root signal converter is using the metal being grounded
Shielding box shields.
6. system according to claim 1, which is characterized in that the multiple root signal converter signal input line is band
The double layer screen line of graphite linings, signal input line are fixed.
7. system according to claim 1, which is characterized in that the signal input part of the multiple root signal converter is adopted
The mode to be put in a skylight with porcelain substrate, signal wire are printed directly on circuit board.
8. system according to claim 1, which is characterized in that the logarithmic transformation circuit includes the computing being electrically connected and puts
Big device, transistor, resistance, capacitance, the operational amplifier are AD549 or OPA129, and the transistor is triode to pipe
MAT01 or field-effect are to pipe AD830.
9. carrying out the method for micro current using the system described in claim 1-8, comprise the following steps：
Step S1, the input terminal of the multiple root signal converter receives the micro current signal to be measured, and it is carried out more
Th Root signal converts, and output analog voltage signal is sent to analog-digital conversion circuit as described；
The analog voltage signal is converted into digital signal by step S2, analog-digital conversion circuit as described, is sent to the microprocessor
Circuit；
Step S3, the microprocessor circuit receive the digital signal, carry out repeatedly square calculation process by software program, most
The value of the current signal to be measured is restored afterwards, completes current measurement.
10. the according to the method described in claim 9, it is characterized in that, mode of multiple root signal conversion described in step S1
Comprise the following steps：
The multiple root signal converter receives the micro current signal to be measured and the reference current signal, and to two institutes
State current signal and carry out logarithmic transformation respectively, obtain two and the current signal into logarithmic relationship voltage signal be sent to it is described
Adder；
The adder is sent to the exponential transform circuit after summing to described two voltage signals；
The exponential transform circuit after the exponential transform with progress to obtaining analog voltage signal, the analog voltage signal
It is the multiple root signal of the electric current to be measured.
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| 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 |
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