CN108880547A - Bridge circuit zero offset on-line correction method based on electric current injection - Google Patents
Bridge circuit zero offset on-line correction method based on electric current injection Download PDFInfo
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- CN108880547A CN108880547A CN201810959935.0A CN201810959935A CN108880547A CN 108880547 A CN108880547 A CN 108880547A CN 201810959935 A CN201810959935 A CN 201810959935A CN 108880547 A CN108880547 A CN 108880547A
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- 238000002347 injection Methods 0.000 title claims abstract description 21
- 239000007924 injection Substances 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims abstract description 20
- 230000003321 amplification Effects 0.000 claims abstract description 9
- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 9
- 238000006243 chemical reaction Methods 0.000 claims abstract description 4
- 238000005259 measurement Methods 0.000 abstract description 6
- 238000001514 detection method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000005611 electricity Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 241000208340 Araliaceae Species 0.000 description 1
- 235000005035 Panax pseudoginseng ssp. pseudoginseng Nutrition 0.000 description 1
- 235000003140 Panax quinquefolius Nutrition 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 235000008434 ginseng Nutrition 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000005405 multipole Effects 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/10—Calibration or testing
- H03M1/1009—Calibration
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/32—Modifications of amplifiers to reduce non-linear distortion
- H03F1/3211—Modifications of amplifiers to reduce non-linear distortion in differential amplifiers
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/45—Differential amplifiers
- H03F3/45071—Differential amplifiers with semiconductor devices only
- H03F3/45479—Differential amplifiers with semiconductor devices only characterised by the way of common mode signal rejection
- H03F3/45928—Differential amplifiers with semiconductor devices only characterised by the way of common mode signal rejection using IC blocks as the active amplifying circuit
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- Engineering & Computer Science (AREA)
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- Theoretical Computer Science (AREA)
- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Measurement Of Current Or Voltage (AREA)
Abstract
The present invention relates to a kind of bridge circuit zero offset on-line correction methods based on electric current injection, bridge output connects the differential signal input of current feedback instrument amplifier A1 respectively, and reference voltage sets resistance and follower A2 and provides reference data voltage to instrument amplifier A1；Instrument amplifier A1 output termination analog-digital converter, the zero offset value that analog-digital converter ADC acquires current electric bridge output is sent into microprocessor after analog-to-digital conversion, microprocessor output signal is after digital analog converter is handled, the indirect current feedback end FB that resistance RA feeds back to instrument amplifier A1 is injected by feedback current, realize that bridge output signal removes zero-bit imbalance before amplification, to improve the output voltage swing of actually active signal, be conducive to improve Measurement Resolution and precision.In circuit use process, internal and external environment makes former zero offset change, and on-line automatic can be readjusted using this method.
Description
Technical field
The present invention relates to a kind of measuring technique, in particular to a kind of bridge circuit zero offset based on electric current injection is online
Bearing calibration.
Background technique
Bridge measuring circuit is generallyd use in the signal detections such as strain, bridge output signal is differential signal, exemplary process
Method is to be followed by three amplifier instrument amplifiers to carry out differential amplification and common mode removal.Ideally, electric bridge exports when non-loaded
It should be zero, but this is only just able to achieve in the four of bridge arm resistance or identical foil gauge resistance value.In practice due to existing
Inevitable component foozle or strain gauge adhesion fabrication error, there are difference imbalance electricity for electric bridge when leading to non-loaded
Pressure, offset voltage and measured signal voltage are amplified to output end with same multiple, lead to that there are very important zero-bit is inclined
It sets, in low-power dissipation system under the lower and lower trend of supply voltage, electric bridge imbalance may occupy the output of significant proportion
The amplitude of oscillation, to influence the measurement range and measurement accuracy of system, therefore in electric bridge detection application, it is necessary to try to carry out zero offset
It corrects to eliminate the influence of electric bridge offset voltage.
The currently used mode for eliminating zero offset has following several：(1) apply anti-electricity in instrument amplifier reference end
Pressure, the main deficiency of this method are that the voltage adjusted on reference end can not if the prime of amplifier has been saturated
Achieve the purpose that eliminate zero offset；(2) electric bridge is shunted using non-essential resistance appropriate, there are poor universality, adjustment is difficult
Limitation；(3) amplified by multipole, reduce the gain coefficient of every level-one, remove zero offset step by step, this needs to increase additional
Device, cause circuit structure complicated and exceptional space or cost overhead；(4) circuit gain is reduced, it is complete with high resolution A/D C
At Digital output, biasing is removed in software, and that there are actual effects is limited, high resolution A/D C higher cost unfavorable for this.
Summary of the invention
The present invention be directed to eliminated in electric bridge detection zero offset method there are the problem of, propose and a kind of infused based on electric current
The bridge circuit zero offset on-line correction method entered may be implemented bridge output signal and remove zero-bit imbalance before amplification,
To improve the output voltage swing of actually active signal, be conducive to improve Measurement Resolution and precision.Simultaneously can online at any time from
It is dynamic to be adjusted.
The technical scheme is that：A kind of bridge circuit zero offset on-line correction method based on electric current injection, electricity
Bridge output end connects the differential signal input of current feedback instrument amplifier A1 respectively, and reference voltage sets resistance and follows
Device A2 provides reference data voltage to instrument amplifier A1；Instrument amplifier A1 output termination analog-digital converter, analog-digital converter
The zero offset value that ADC acquires current electric bridge output is sent into microprocessor after analog-to-digital conversion, and microprocessor output signal is sent
Enter digital analog converter, digital analog converter output injects resistance RA by feedback current and forms Injection Current, and Injection Current is fed back to
The indirect current feedback end FB of instrument amplifier A1, to change the current potential of feedback end FB, before instrument amplifier A1 amplification
Remove imbalance.
The instrument amplifier A1 output meets two gains configuration resistance R1 and R2, and wherein gain configuration resistance R2 is connected across
Between instrument amplifier A1 output end and indirect current feedback end FB, gain configuration resistance R1 is connected across instrument amplifier A1 output
Between reference end REF and indirect current feedback end FB.
The resistance value in parallel of described two gain configuration resistance R1 and R2 are no more than 30K Ω, reduce circuit noise.
The follower A2 is high input impedance operational amplifier, two reference voltage setting resistance R3 and R4 series connection
Tie point connects follower A2 non-inverting input terminal, and follower A2 inverting input terminal and output end connect instrument amplifier A1 output ginseng jointly
Examine end REF.
The beneficial effects of the present invention are：The present invention is based on the bridge circuit zero offset on-line correction sides of electric current injection
Method may be implemented bridge output signal and remove zero-bit imbalance before amplification, so that the output voltage swing of actually active signal is improved,
Be conducive to improve Measurement Resolution and precision.Meanwhile having circuit structure simple, adjustment facilitates advantage.In circuit use process
In, it, can be online using this method if environmental condition, sensor sluggishness or long term drift etc. make former zero offset change
It is readjusted automatically at any time.
Detailed description of the invention
Fig. 1 is formed substantially for circuit of the present invention and working principle diagram；
Fig. 2 is circuit diagram of the embodiment of the present invention.
Specific embodiment
Bridge circuit zero offset on-line correction circuit as shown in Figure 1 based on electric current injection forms substantially and working principle
Figure, including instrument amplifier A1, follower A2, gain configuration resistance R1 and R2, reference voltage setting resistance R3 and R4, feedback electricity
Stream injection resistance RA, analog-digital converter ADC, digital analog converter DAC.
The instrument amplifier A1 feeds back (ICF) type instrument amplifier for indirect current, puts in addition to having conventional instrument
Greatly except the differential signal input of device, reference voltage end and output end, there are also indirect current feedback end FB, and electric current may be implemented
Injection.
Bridge output connects the differential signal input of instrument amplifier A1 respectively, and it includes R2 and R1 two that gain, which configures resistance,
A resistance, R2 are connected across between instrument amplifier A1 output end and indirect current feedback end FB, and R1 is connected across instrument amplifier A1
It exports between reference end REF and indirect current feedback end FB.In order to reduce circuit noise, the resistance value in parallel of R1 and R2 should be no more than
30KΩ。
The follower A2 is high input impedance operational amplifier, is that instrument amplifier A1 is defeated together with resistance R3 and R4
Reference end REF provides reference data voltage out.Reference voltage value presses formulaIt sets, wherein VcFor circuit
Operating voltage.
The analog-digital converter ADC is connected to the output end of instrument amplifier A1, for acquiring current electric bridge output
Zero offset value, and output of digital analog converter DAC is controlled with this, realize detection and the feedback compensation of online zero offset.
The feedback current injection resistance RA connects between digital analog converter DAC output end and indirect current feedback end FB,
Feedback current injection resistance RA and digital analog converter DAC is formed together Injection Current, thus change the current potential of feedback node FB, into
And achieve the effect that remove imbalance before amplification.
Embodiment circuit diagram as shown in Figure 2, it is assumed that bridge excitation voltage and circuit voltage are 3.3V, and electric bridge is expired
Range output is ± 15mV, and electric bridge zero-bit offset voltage is likely to be at the range of ± 25mV.In order to obtain required sensitivity, circuit
Gain need to be that the input range of 100, ADC is 0V to 3.3V.Since the output of electric bridge can be positive, or it is negative, therefore answer
It is 1.65V that circuit zero-bit, which is arranged, to export.Amplifier maximum output is no more than power rail 0-3.3V, in this way without electric bridge zero-bit
In the case that offset voltage corrects, it is 41 that the maximum gain of amplifier A1, which can only achieve, is not able to satisfy sensitivity required for measurement
It is required that, it is therefore necessary to electric bridge zero-bit offset voltage is removed before amplification.
Using bridge circuit zero offset correcting circuit provided by the invention, amplifier of electrical bridge A1 is ICF instrument amplifier
AD8237, amplifier A2 are two-way low-power consumption rail-to-rail amplifier AD8506, R3 and R4 electric by the zero of A1 by the road the A output of A2
Flat output is set as intermediate power supplies+1.65V.The gain that resistance R1 and R2 are amplifier A1 configures, and the output of A1 is by low-power consumption 16
ADC AD7705 digitlization, and 10 DAC LTC1661 outputs are controlled according to sampled result by microprocessor, the output is through A2's
The road B, which is followed, forms corresponding injection circuit by RA, so that electric bridge be made to be adjusted to 0 automatically.
The design parameter provided using Fig. 2, circuit gain 100.6 can provide the electric bridge imbalance adjustment model of ± 32mV
It encloses, for 10 DAC, adjusting step is 62.5 μ V, and the maximum residual offset of such output end is 0.625mV.
Fig. 1 is basic principle, and Fig. 2 is practical embodiment.The two principle be it is identical, only increased in embodiment with
With having increased and decreased the robustness of circuit.
Claims (4)
1. a kind of bridge circuit zero offset on-line correction method based on electric current injection, which is characterized in that bridge output point
The differential signal input of current feedback instrument amplifier A1 is not connect, and reference voltage sets resistance and follower A2 to instrument
Amplifier A1 provides reference data voltage；Instrument amplifier A1 output termination analog-digital converter, analog-digital converter ADC acquisition are current
The zero offset value of electric bridge output is sent into microprocessor after analog-to-digital conversion, and microprocessor output signal is sent into digital-to-analogue conversion
Device, digital analog converter output inject resistance RA by feedback current and form Injection Current, and Injection Current feeds back to instrument amplifier
The indirect current feedback end FB of A1 removes imbalance before instrument amplifier A1 amplification to change the current potential of feedback end FB.
2. the bridge circuit zero offset on-line correction method according to claim 1 based on electric current injection, which is characterized in that
The instrument amplifier A1 output meets two gains configuration resistance R1 and R2, and wherein gain configuration resistance R2 is connected across instrument amplification
Between device A1 output end and indirect current feedback end FB, gain configuration resistance R1 is connected across instrument amplifier A1 output reference end
Between REF and indirect current feedback end FB.
3. the bridge circuit zero offset on-line correction method according to claim 2 based on electric current injection, which is characterized in that
The resistance value in parallel of described two gain configuration resistance R1 and R2 are no more than 30K Ω, reduce circuit noise.
4. the bridge circuit zero offset on-line correction method according to claim 1 or claim 2 based on electric current injection, feature exist
In the follower A2 is high input impedance operational amplifier, and two reference voltage settings resistance R3 and R4 are connected in series
Point connects follower A2 non-inverting input terminal, and follower A2 inverting input terminal and output end connect instrument amplifier A1 output reference end jointly
REF。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201810959935.0A CN108880547A (en) | 2018-08-21 | 2018-08-21 | Bridge circuit zero offset on-line correction method based on electric current injection |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810959935.0A CN108880547A (en) | 2018-08-21 | 2018-08-21 | Bridge circuit zero offset on-line correction method based on electric current injection |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114894223A (en) * | 2022-04-27 | 2022-08-12 | 北京开拓航宇导控科技有限公司 | Novel bridge sensor signal conditioning circuit and method |
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