CN106289464A - A kind of two-wire system faint strain bridge signal transmitting device - Google Patents
A kind of two-wire system faint strain bridge signal transmitting device Download PDFInfo
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- CN106289464A CN106289464A CN201610877392.9A CN201610877392A CN106289464A CN 106289464 A CN106289464 A CN 106289464A CN 201610877392 A CN201610877392 A CN 201610877392A CN 106289464 A CN106289464 A CN 106289464A
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- 238000013508 migration Methods 0.000 claims abstract description 20
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- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 17
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- 238000005259 measurement Methods 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 238000005303 weighing Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 2
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- 229920001971 elastomer Polymers 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
- G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
- G01G3/14—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing measuring variations of electrical resistance
- G01G3/142—Circuits specially adapted therefor
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- Measuring Fluid Pressure (AREA)
Abstract
The open one of the present invention is applicable to the two-wire system current mode transmitter of output voltage change the most small (some millivolts), the zero migration resistance-type strain bridge signal of (suitable with exporting change amount, even greater than output voltage variable quantity) the most greatly.This transmitter includes the compositions such as faint strain bridge, differential amplifier circuit, zero migration circuit, V/I modular converter, power supply and output loop.Sensor bridge output faint and there is the voltage signal of zero migration be input to the first differential amplifier and carry out one-level amplification, its output voltage adjusts voltage with zero migration again and carries out the differential amplification in the second level, its output voltage is input to V/I modular converter again, being converted to 4～20mA electric current outputs under the control of output electric current adjustment amount, V/I module provides power supply and reference to strain bridge and amplifying circuit simultaneously.Circuit of the present invention is simple, the linearity good, cost performance is high, easy-to-connect.
Description
Technical field
The present invention relates to detection technique and automation equipment field, it is more particularly related to a kind of faint strain
Bridge signal conversion transmitter meter.
Background technology
Resistance strain type sensor is widely used in power, pressure, acceleration, the isoparametric measurement of quality, and it is the most former
Reason is that elastomer (flexible member, sensitive beam etc.) produces elastic deformation under external force, makes the resistance being pasted onto its surface answer
Becoming sheet (conversion element) also in company with producing deformation, after resistance strain gage deformation, its resistance will change (increase or reduce), then
Through corresponding measuring circuit (Huygens's electric bridge), the change of resistance is converted to voltage signal, thus completes relevant to power
Parameters Transformation is the process of the signal of telecommunication, and its typical case's application is exactly electronic weighing appliance.
But, most resistance-type strain bridge output voltage signal sensitivity are relatively low, and voltage variety is less, and zero point is inclined
Shifting amount is relatively big, even suitable with voltage variety, and first signal conditioning and conversion difficulty are relatively big, hangs with certain model that market is bought
As a example by arm beam strain bridge-type 1kg range LOAD CELLS, when using reference current IrefDuring the electric current bridge of=1.6mA, after tested,
Weighing when 0～800g changes, its null offset has reached 1.3mV, and maximum exporting change amount is only 1.0mV.
Industrial most widely used be 4～20mA electric currents to transmit analog quantity, because current signal is not susceptible to interference, and
And the internal resistance of current source is infinitely great, precision will not be impacted, such that it is able to realize hundreds of by conductor resistance series connection in the loop
The transmission of rice.Therefore, faint strain bridge signal is converted to 4～20mA electric currents and is transmitted by industrial typically requiring, and on
Stating sensor output voltage change small, zero point offset amount is relatively big, and conditioning and conversion for signal add difficulty, generally undoubtedly
Need to use high-precision adc to carry out sampling and microprocessor processes, or the three-wire system being equipped with producer's offer processes circuit
Module converts, and its circuit is complicated, cost is high, wiring relatively two-wire system instrument is complicated.
Search current mode transmitter Patents document, the high-temperature fusant automatic zero set pressure of Wu Zhenghui, dragon rosy clouds et al. invention
Power transmitter have employed microprocessor and software programming to realize zero point and full scale adjusts automatically and 4～20mA electric currents output；
The transmitter of the force balancing type of strain-type displacement detecting element of Wang Kechong invention, its overall structure is complex, signal condition and
Resistance-strain bridge zero migration cannot be fallen by translation circuit itself automatically, and this invention requires that bridge output voltage bound meets
The quantitative relation (i.e. zero point offset amount and voltage variety meets 1: 4 quantitative relation) of 1: 5, needs by a negative feedback closed loop
Bascule completes conversion and ensures certainty of measurement and the linearity.The present invention then by simple signal condition, amplify, adjust
Whole and V/I translation circuit realizes the high multiple of small-signal and amplifies and zero migration, it is not necessary to high-precision AD collection adds digital processing
Or complex feedback bascule can obtain higher conversion accuracy and the linearity.
Summary of the invention
The technical problem to be solved is to provide a kind of two-wire system current mode transmitter, and it can be to change in voltage
Measure the little strain to some millivolts and Null-Offset voltage suitable with variable quantity (even voltage variety is less than zero point offset amount)
Bridge measurement signal carries out processing, convert and exporting.
In order to solve described technical problem, the invention provides a kind of two-wire system faint strain bridge signal transmitting device, its
Feature is to use pure analog circuit process signal and convert, and it includes faint strain bridge, differential amplifier circuit, zero point
Off-centre circuit, V/I modular converter, power supply and output loop etc. form.Sensor bridge output faint and there is zero migration
Voltage signal be input to the first differential amplifier and carry out one-level amplification, its output voltage adjusts circuit output again with zero migration
Voltage carry out the differential amplification in the second level, its output voltage is input to V/I modular converter again, output electric current adjustment amount control
Under be converted to 4～20mA electric currents outputs, by potentiometer can zeroing side-play amount and output amplification easily, and can
Eliminate operational amplifier offset voltage, the offset current impact on the conversion accuracy of small-signal.
Preferably, needed for the strain bridge of described transmitter, differential amplifier circuit, zero migration adjustment etc. process circuit
Power supply and the reference wanted are provided by V/I modular converter, it is not necessary to additionally providing power supply, system also exports non-thread with strain bridge
Property automatic compensation function, designed by scheme optimization, aforementioned processing circuit power consumption be less than 4mA, two with 4mA as zero point can be realized
Line system is powered and exports.
Preferably, described transmitter also includes power supply and output loop, as long as accessing 24V unidirectional current at output loop
Source, the most exportable current signal, and output loop have reverse connecting protection, and power supply can access loop by any direction.
The present invention at least includes following beneficial effect:
(1) little to some millivolts and Null-Offset voltage (even voltage variety suitable with variable quantity to voltage variety
Less than zero point offset amount) strain bridge measure signal, the present invention can effectively and critically be transformed to 4～20mA current signals
Export.
(2) pure analog circuit is used signal to be processed and converts, it is not necessary to high-precision AD collection adds digital processing or multiple
Miscellaneous feedback equalization device, simple in construction, with low cost.
(3) zero migration and output amplification are easy to adjust, and offset voltage of amplifier, offset current are to small-signal
Conversion accuracy is without impact, high with non-linear automatic compensation, certainty of measurement and the linearity.
(4) two-wire system is powered and exports, and transmitter is distinguished without both positive and negative polarity, easy-to-connect, simple, facilitates remote transmission.
Part is embodied by the further advantage of the present invention, target and feature by description below, and part also will be by this
Invention research and practice and be understood by the person skilled in the art.
Accompanying drawing explanation
Fig. 1 is the structural representation of two-wire system of the present invention faint strain bridge signal transmitting device.
Fig. 2 is the circuit diagram of two-wire system of the present invention faint strain bridge signal transmitting device.
Fig. 3 (a) and (b) are respectively design example at uncompensated resistance RLINWith compensation resistance RLINDuring=9.33k Ω, tested
Variation relation curve chart between amount and output electric current.
Detailed description of the invention
The present invention is described in further detail below in conjunction with the accompanying drawings, to make those skilled in the art with reference to description literary composition
Word can be implemented according to this.
Should be appreciated that used herein such as " have ", " comprising " and " including " term are not precluded from one or many
Other element individual or the existence of a combination thereof or interpolation.
The present invention provides a kind of two-wire system faint strain bridge signal transmitting device, use pure analog circuit to signal at
Reason and conversion, its composition structure is as it is shown in figure 1, include that faint strain bridge the 1, first differential amplifier 2, zero migration adjust electricity
The compositions such as road the 3, second differential amplifier 4, output matrix current adjustment circuit 5, V/I modular converter 6, power supply and output loop 7.
Transmitter operation principle is: faint strain bridge 1 output faint and have zero migration voltage signal input
One-level amplification is carried out to the first differential amplifier 2, defeated together with the voltage that its output voltage adjusts circuit 3 output with zero migration again
Entering the second differential amplifier 4 and carry out the differential amplification in the second level, its output voltage is input to V/I modular converter 6 again, at output electric current
Be converted to 4～20mA electric currents under the control action of adjustment circuit 5 exported by output loop 7, wherein, can be square by potentiometer
Just zeroing side-play amount and output amplification.
It is illustrated in figure 2 the example of a kind of two-wire system faint strain bridge signal transmitting device, is i.e. embodied as circuit.This is real
Example circuit is a two-wire system pick-up that certain model cantilever beam strain bridge type weighing sensor carries out 4～20mA current transformations
Device.
The cantilever beam strain bridge type weighing sensor maximum range that example uses is 1kg, when using reference current Iref=
Applying 0～800g weight on a cantilever beam during the electric current bridge of 1.6mA, output voltage excursion is 1.3～2.3mV, meets zero
Point skew is big, measures the change in voltage feature less than zero point offset amount.
Described first differential amplifier 2 and the second differential amplifier 4 all use low cost, in high precision, low-power consumption instrument puts
Big device AD627, its gain ranging is 1～1000, and only needs a non-essential resistance to arrange gain, and wherein, first differential puts
1.3～the 2.3mV differential voltages that electric bridge is exported by big device AD627 carry out primary amplification, RcFor its Gain tuning resistance, use
The 1k Ω potentiometer of 3296 encapsulation, adjusts potentiometer RcResistance, Gain tuning is about 500 so that it is output voltage-to-ground model
Enclose about 0.65～1.15V.
Described V/I modular converter 6 uses the 4～20mA current source chip XTR105 that single is integrated, and it has the lowest tune
Whole property error, has two high-precision mirror current sources of 0.8mA and the reference voltage source of 5.1V, 1mA output capacity, if
Counting provides 1.6mA current references by backward micro-power transformation bridges in parallel for two current sources thus constitutes current mode electric bridge, exportable 1.3～
2.3mV measures signal, and to two AD627 instrument amplifiers and adjusts circuit confession by the reference voltage source of 5.1V, 1mA capacity
Electricity.
Described zero migration adjusts circuit 3 and is attempted by 5.1V by a 5M Ω fixed resistance and a 1M Ω potentiometer series connection
On reference voltage source, the output of potentiometer centre cap adjusts voltage, and it adjusts voltage and can change in the range of 0～0.85V, this electricity
Pressure can be higher precision offset 0.65V Null-Offset voltage, and the electric current in this loop is only 0.85 μ A, and power consumption is extremely low.
Voltage and zero migration that first differential amplifier is exported by described second differential amplifier 4 (AD627) adjust electricity
Pressure carries out differential amplification, is not connected to gain setting resistor, and amplification is 1.In Fig. 2,1k Ω potentiometer RCMAnd it is connected in parallel
0.01 μ F electric capacity is held between 6 feet of XTR105 with being connected on electric bridge reference, forms bridge power supply loop, and meanwhile, electric bridge is with reference to ground
End (i.e. RCMLeft end) be connected to 5 ends (output reference edge) of the second differential amplifier 4 and V/I modular converter XTR105 2 ends (defeated
Enter Voltage Reference end), 6 end output about 1.25～the voltage-to-grounds of 1.75V of the second differential amplifier 4, i.e. by electric bridge
1.6mA electric current is at RCMThe pressure drop of upper formation improves output voltage starting point but provides its institute for XTR105 chip dexterously simultaneously
The common mode input of the minimum 1.25V required.
Described through second differential amplifier 4 amplify after voltage with the form of differential voltage be input to XTR105 13 ends (+
VIN) and 2 end (-VINBetween), the voltage transformation of common mode 1.25V, differential mode 0～0.5V range is that 4mA is by XTR105 automatically
Initial current signal, its input/output relation is
Io=4+40 VIN/RG (1)
In formula, IoFor output electric current, unit is mA；VINFor input differential mode voltage, unit is V；RGFor described output electric current
Adjusting circuit 5, namely the Gain tuning resistance value of XTR105, unit is Ω, and it can adjust in 0～2000 Ω, will output
Current adjustment resistor RGIt is adjusted in about 1250 Ω can make its output curent change scope is arranged on 4～20mA.
Described power supply and output loop 7 are connected to NPN type triode Q1(BU406), to improve its fan-out capability, reduce
XTR105 chip generates heat, and its B pole is connected with 9 ends of XTR105, and C pole is connected with 10 ends of XTR105, E pole and 8 ends of XTR105
It is connected.24V DC source is chip power supply by current loop, D1～D4 simultaneously arranged in circuit uses IN4148 diode
Constitute rectifier bridge, reverse power connection can be prevented so that this transmitter power supply wiring direction can arbitrarily exchange, and connect D5 (employing
36V Zener diode 1N4753), absorbable surge current, plays overvoltage protection effect, the 0.1 μ F electric capacity that output loop connects
Play pressure stabilization function, finally at power supply, rectifier bridge, XTR105 and BU406, load RLThe loop of upper composition is flow through 4～20mA
Electric current.
Further, the 12 end (V of XTR105LIN) and strain bridge export between positive pressure side by the potentiometer of 20k Ω
RLINLink together, the nonlinear compensation electric current compensated resistance R that XTR105 is providedLINIt is input to the lower-left bridge of strain bridge
Arm, in order to carry out non-linear automatic compensation to the exporting change amount of strain bridge, by RLINResistance is adjusted to suitably to be worth can be notable
Improving output linearity degree and output accuracy, Fig. 3 (a) and (b) respectively design example (i.e. 800g range cantilever beam strain bridge-type claim
Weight transmitter) at uncompensated resistance RLINResistance R is compensated with adjustingLINDuring=9.33k Ω, measured and output electric current between change
Change relation curve.
Although embodiment of the present invention are disclosed as above, but it is not restricted in description and embodiment listed
Use.It can be applied to various applicable the field of the invention completely.Can be easily for those skilled in the art
Realize other amendment.Therefore, under the general concept limited without departing substantially from claim and equivalency range, the present invention does not limit
In specific details with shown here as the legend with description.
Claims (6)
1. a two-wire system faint strain bridge signal code type transmitter, this transmitter includes faint strain bridge, differential puts
The compositions such as big circuit, zero migration circuit, V/I modular converter, power supply and output loop.Faint and the tool of sensor bridge output
The voltage signal having zero migration is input to the first differential amplifier and carries out one-level amplification, and its output voltage is adjusted with zero migration again
Whole voltage carries out the differential amplification in the second level, and its output voltage is input to V/I modular converter again, in the control of output electric current adjustment amount
Under be converted to 4～20mA electric currents output.
Two-wire system the most according to claim 1 faint strain bridge signal transmitting device, is characterized in that: this transmitter input electricity
Pressure variable quantity may diminish to some millivolts, and input voltage zero point offset amount can be with voltage variety quite (even zero point offset amount
More than change in voltage), the voltage signal for this process more difficulty can effectively and critically be transformed to 4～20mA electricity
Stream signal exports.
Two-wire system the most according to claim 1 faint strain bridge signal transmitting device, is characterized in that: this transmitter uses pure
Signal is processed by analog circuit, and it first carries out one-level differential amplification to input voltage and deducts Null-Offset voltage again so that
Voltage Cortrol resolution and precision significantly improve, and input V/ after second level differential amplification adds certain common-mode voltage
I modular converter, by potentiometer can zeroing side-play amount and output amplification easily, and operational amplifier can be eliminated
The impact on the conversion accuracy of small-signal of offset voltage, offset current.
Two-wire system the most according to claim 1 faint strain bridge signal transmitting device, is characterized in that: strain bridge, differential
Power supply and reference required for the circuit such as amplifying circuit, zero migration adjustment are provided by V/I modular converter, it is not necessary to additionally provide
Power supply, can realize pure two-wire system and power and export, and compensated by the nonlinear compensation electric current that provided by V/I modular converter
Resistance is input to a brachium pontis of strain bridge and realizes mission nonlinear and automatically compensate, and improves output linearity degree and conversion accuracy.
Two-wire system the most according to claim 4 faint strain bridge signal transmitting device, is characterized in that: strain bridge, differential
The power consumption of the circuit such as amplifying circuit, zero migration adjustment is extremely low, and its total current is less than 4mA, thus can realize with 4mA as zero point
Current signal exports.
Two-wire system the most according to claim 1 faint strain bridge signal transmitting device, is characterized in that: in output loop only
24V DC source to be accessed, the most exportable current signal, and output loop have reverse connecting protection, and power supply can be connect by any direction
Entry loop.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201610877392.9A CN106289464A (en) | 2016-09-30 | 2016-09-30 | A kind of two-wire system faint strain bridge signal transmitting device |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201610877392.9A CN106289464A (en) | 2016-09-30 | 2016-09-30 | A kind of two-wire system faint strain bridge signal transmitting device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113138162A (en) * | 2021-06-22 | 2021-07-20 | 南京高华科技股份有限公司 | Steel wire rope state monitoring device and monitoring method |
| CN114777894A (en) * | 2022-04-06 | 2022-07-22 | 深圳市凌阳电子有限公司 | Human body scale based on two-wire system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62162927A (en) * | 1986-01-13 | 1987-07-18 | Tanita:Kk | Span and zero point adjusting device for load cell scale |
| WO1988006719A1 (en) * | 1987-03-05 | 1988-09-07 | The Secretary Of State For Defence In Her Britanni | Transducer signal conditioner |
| CN2580406Y (en) * | 2002-11-13 | 2003-10-15 | 北京安控科技发展有限公司 | Modulation circuit of thermal resistance, angular displacement and loading combined signal of automation control terminal |
| CN201417184Y (en) * | 2009-04-23 | 2010-03-03 | 广东美的电器股份有限公司 | two-wire temperature transmitter |
| CN207163548U (en) * | 2016-09-30 | 2018-03-30 | 南京林业大学 | A kind of faint strain bridge signal transmitting device of two-wire system |
-
2016
- 2016-09-30 CN CN201610877392.9A patent/CN106289464A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62162927A (en) * | 1986-01-13 | 1987-07-18 | Tanita:Kk | Span and zero point adjusting device for load cell scale |
| WO1988006719A1 (en) * | 1987-03-05 | 1988-09-07 | The Secretary Of State For Defence In Her Britanni | Transducer signal conditioner |
| CN2580406Y (en) * | 2002-11-13 | 2003-10-15 | 北京安控科技发展有限公司 | Modulation circuit of thermal resistance, angular displacement and loading combined signal of automation control terminal |
| CN201417184Y (en) * | 2009-04-23 | 2010-03-03 | 广东美的电器股份有限公司 | two-wire temperature transmitter |
| CN207163548U (en) * | 2016-09-30 | 2018-03-30 | 南京林业大学 | A kind of faint strain bridge signal transmitting device of two-wire system |
Non-Patent Citations (2)
| Title |
|---|
| 惠力, 于锋, 綦声波, 朱洪海: "基于XTR105的气温传感器", 自动化与仪表, no. 06, 5 December 2002 (2002-12-05), pages 13 - 15 * |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113138162A (en) * | 2021-06-22 | 2021-07-20 | 南京高华科技股份有限公司 | Steel wire rope state monitoring device and monitoring method |
| CN114777894A (en) * | 2022-04-06 | 2022-07-22 | 深圳市凌阳电子有限公司 | Human body scale based on two-wire system |
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