CN202533482U - 4-20 ma current transmitter circuit - Google Patents

4-20 ma current transmitter circuit Download PDF

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Publication number
CN202533482U
CN202533482U CN2012200604629U CN201220060462U CN202533482U CN 202533482 U CN202533482 U CN 202533482U CN 2012200604629 U CN2012200604629 U CN 2012200604629U CN 201220060462 U CN201220060462 U CN 201220060462U CN 202533482 U CN202533482 U CN 202533482U
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China
Prior art keywords
resistance
operational amplifier
circuit
connect
resistor
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Expired - Fee Related
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CN2012200604629U
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Chinese (zh)
Inventor
陈一中
王宏华
严垚
尹祥顺
李军民
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YANGZHOU SHUNFENG ELECTRICAL APPLIANCE CO Ltd
Hohai University HHU
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YANGZHOU SHUNFENG ELECTRICAL APPLIANCE CO Ltd
Hohai University HHU
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Priority to CN2012200604629U priority Critical patent/CN202533482U/en
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Publication of CN202533482U publication Critical patent/CN202533482U/en
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Abstract

The utility model discloses a 4-20 mA current transmitter circuit. The 4-20 mA current transmitter circuit is characterized in that the 4-20 mA current transmitter circuit comprises an input circuit, an electric level transformation circuit, an inverting circuit and a current transmission circuit, a signal output terminal of a first operational amplifier in the input circuit is connected to an inverting input terminal of a second operational amplifier in the electric level transformation circuit through a third resistor, a signal output terminal of the second operational amplifier is connected to an inverting input terminal of a third operational amplifier in the inverting circuit through a sixth resistor, and a signal output terminal of the third operational amplifier is connected to a non-inverting input terminal of a fourth operational amplifier in the current transmission circuit. The 4-20 mA current transmitter circuit has the advantages of simple circuit structure, low cost, and good performance. In the specific product implementation, only an integrated circuit of four operational amplifiers, a few low-power resistors and a triode are needed, which is convenient to realize.

Description

4-20mA current transducer circuits
Technical field
The utility model relates to a kind of 4-20mA current transducer circuits as industrial field device running status remote monitoring.
Background technology
In industry spot, analog current output can realize the state of remote monitoring motor operation, if being voltage signal after the signal of collection is conditioned and carrying out Long line transmission, can produce problems with：First, because the signal of transmission is voltage signal, transmission line can be easy for being disturbed by noise；Second, the distributed resistance of transmission line can produce voltage drop；3rd, the operating voltage that instrument amplifier how is provided at the scene is also a problem；In order to solve the above problems and avoid the influence of correlated noise, industry spot largely transmits signal using electric current, and interference is not susceptible to using current signal；It is that, because requirement of explosion proof, spark energy caused by 20mA current switching is not enough to the gas that ignites, and is used for the low alarm setting of various failures less than 4mA that the upper limit, which takes 20mA,；Only so the reason for not taking 0mA is in order to be able to detect broken string, 4mA is not less than during normal work, when transmission line is because of failure to trip, loop current is reduced to 0；
Mainly there are two kinds of solutions at present：
1）Transmitter is exchanged, major loop alternating current directly can be converted into the DC4-20mA constant current ring standard signals by linear scale output, be delivered continuously to reception device, soft initiator selling price is low, and profit is thin so that the cost performance of this scheme to seem be not too high；
2）Integrated chip solution, ADI companies provide a kind of electric current loop transducer driven chip, such as AD694.The voltage conversion of input can be exported for electric current；This chip is great good news, shortcoming for exploitation 4-20mA electric currents：Price is also very high, is not suitable for batch production, which limits the feasibility of this scheme；
Above scheme is limited in Soft Starter of Induction Motor etc low cost due to factors such as price height
Application in electrical equipment.
The content of the invention
The utility model proposes a kind of 4-20mA current transducers circuit, its purpose is intended to overcome the drawbacks described above present in prior art, with circuit structure is simple, low cost, function admirable, the features such as be easy to implement.
Technical solution of the present utility model：Its structure is to include input circuit, level-conversion circuit, negative circuit, electric current transmission circuit, the first operational amplifier wherein in input circuit
Figure 775120DEST_PATH_IMAGE001
Signal output part pass through 3rd resistor
Figure 529449DEST_PATH_IMAGE002
Connect the second operational amplifier in level-conversion circuit
Figure 469723DEST_PATH_IMAGE003
Inverting input, the second operational amplifier
Figure 993109DEST_PATH_IMAGE003
Signal output part pass through the 6th resistanceConnect the 3rd operational amplifier in negative circuit
Figure 585950DEST_PATH_IMAGE005
Inverting input, the 3rd operational amplifier
Figure 126653DEST_PATH_IMAGE005
Signal output part pass through the 8th resistanceConnect the four-operational amplifier in electric current transmission circuit
Figure 105290DEST_PATH_IMAGE007
In-phase input end.
Advantage of the present utility model：Circuit structure is simple, low cost, function admirable, during specific product is implemented, it is only necessary to one piece of four-operational amplifier integrated circuit, and a small amount of small-power resistance and a triode, is easy to implement.
Brief description of the drawings
Accompanying drawing 1 is the circuit theory diagrams of 4-20mA current transducer circuits.
Accompanying drawing 2 is the input and output simulation result figure of 4-20mA current transducer circuits.
Embodiment
Below with reference to accompanying drawing, the circuit connection structure and operation principle of the present invention are described in detail.
Accompanying drawing 1 is compareed, its structure is to include input circuit, level-conversion circuit, negative circuit, electric current transmission circuit, the first operational amplifier wherein in input circuit
Figure 506316DEST_PATH_IMAGE001
Signal output part pass through 3rd resistor
Figure 850709DEST_PATH_IMAGE002
Connect the second operational amplifier in level-conversion circuit
Figure 83107DEST_PATH_IMAGE003
Inverting input, the second operational amplifier
Figure 854754DEST_PATH_IMAGE003
Signal output part pass through the 6th resistance
Figure 493808DEST_PATH_IMAGE004
Connect the 3rd operational amplifier in negative circuit
Figure 376314DEST_PATH_IMAGE005
Inverting input, the 3rd operational amplifierSignal output part pass through the 8th resistance
Figure 609029DEST_PATH_IMAGE006
Connect the four-operational amplifier in electric current transmission circuitIn-phase input end.
Described input circuit includes first resistor
Figure 733160DEST_PATH_IMAGE008
, second resistance
Figure 940150DEST_PATH_IMAGE009
, the first operational amplifier, first resistor
Figure 165781DEST_PATH_IMAGE008
One end connection+5V power supplys, first resistor
Figure 390089DEST_PATH_IMAGE008
The other end connection second resistance
Figure 717165DEST_PATH_IMAGE009
One end, and with the first operational amplifierIn-phase input end be connected, second resistance
Figure 86147DEST_PATH_IMAGE009
The other end be connected to the ground, the first operational amplifier
Figure 114146DEST_PATH_IMAGE001
Inverting input connection output end.
Level shifting circuit includes 3rd resistor
Figure 984144DEST_PATH_IMAGE002
, the 4th resistance
Figure 439396DEST_PATH_IMAGE010
, the 5th resistance
Figure 73639DEST_PATH_IMAGE011
With the second operational amplifier
Figure 639750DEST_PATH_IMAGE003
, 3rd resistor
Figure 879101DEST_PATH_IMAGE002
One end connect the first operational amplifier
Figure 505255DEST_PATH_IMAGE001
Output end, 3rd resistor
Figure 626795DEST_PATH_IMAGE002
The other end connect the 4th resistance
Figure 183547DEST_PATH_IMAGE010
One end, the 5th resistance
Figure 339722DEST_PATH_IMAGE011
One end connect the second operational amplifier
Figure 136776DEST_PATH_IMAGE003
Inverting input, the 5th resistance
Figure 745612DEST_PATH_IMAGE011
The other end connection input, the 4th resistance
Figure 591208DEST_PATH_IMAGE010
The other end connect the second operational amplifier
Figure 601890DEST_PATH_IMAGE003
Output end, the second operational amplifier
Figure 569846DEST_PATH_IMAGE003
In-phase input end connection ground.
Negative circuit includes the 6th resistance
Figure 354393DEST_PATH_IMAGE004
, the 7th resistanceWith the 3rd operational amplifier
Figure 931185DEST_PATH_IMAGE005
, the 6th resistance
Figure 70042DEST_PATH_IMAGE004
One end connect the second operational amplifier
Figure 591154DEST_PATH_IMAGE003
Output end, the 6th resistance
Figure 106449DEST_PATH_IMAGE004
The other end connect the 3rd operational amplifierInverting input and the 7th resistance
Figure 135902DEST_PATH_IMAGE012
One end, the 7th resistance
Figure 393576DEST_PATH_IMAGE012
The other end connect the 3rd operational amplifier
Figure 446983DEST_PATH_IMAGE005
Output end, the 3rd operational amplifier
Figure 286763DEST_PATH_IMAGE005
In-phase input end connection ground.
Electric current transmission circuit includes the 8th resistance, the 9th resistance
Figure 263126DEST_PATH_IMAGE013
, the tenth resistance
Figure 854645DEST_PATH_IMAGE014
, the 11st resistance
Figure 548931DEST_PATH_IMAGE015
, the 12nd resistance
Figure 466072DEST_PATH_IMAGE016
, the 13rd resistance
Figure 922506DEST_PATH_IMAGE017
, the 14th resistance
Figure 317715DEST_PATH_IMAGE018
, four-operational amplifier
Figure 132087DEST_PATH_IMAGE007
, NPN triode
Figure 954550DEST_PATH_IMAGE019
, wherein the 8th resistance
Figure 159266DEST_PATH_IMAGE006
One end connect the 3rd operational amplifierOutput end, the 8th resistance
Figure 27045DEST_PATH_IMAGE006
The other end connection four-operational amplifier
Figure 20409DEST_PATH_IMAGE007
In-phase input end, four-operational amplifier
Figure 961689DEST_PATH_IMAGE007
In-phase input end connect the 14th resistance
Figure 698701DEST_PATH_IMAGE018
One end, four-operational amplifier
Figure 222086DEST_PATH_IMAGE007
Inverting input connect the 9th resistance
Figure 651930DEST_PATH_IMAGE013
One end, the 9th resistance
Figure 831239DEST_PATH_IMAGE013
The other end connection ground, the tenth resistance
Figure 106362DEST_PATH_IMAGE014
One end connection four-operational amplifier
Figure 749833DEST_PATH_IMAGE007
Inverting input, the tenth resistanceThe other end connect the 12nd resistance
Figure 502337DEST_PATH_IMAGE016
One end, four-operational amplifier
Figure 581151DEST_PATH_IMAGE007
Output end connect the 11st resistance
Figure 79129DEST_PATH_IMAGE015
One end, the 11st resistance
Figure 788459DEST_PATH_IMAGE015
The other end connection transistor
Figure 739097DEST_PATH_IMAGE019
Base stage, transistor
Figure 621603DEST_PATH_IMAGE019
Colelctor electrode connection+5V power supplys, transistor
Figure 974086DEST_PATH_IMAGE019
Emitter stage connect the 12nd resistance
Figure 916635DEST_PATH_IMAGE016
One end, the 12nd resistance
Figure 541520DEST_PATH_IMAGE016
The other end and the 13rd resistance
Figure 962137DEST_PATH_IMAGE017
, the 14th resistance
Figure 434707DEST_PATH_IMAGE018
One end be connected and be connected in the output end of transmitter, the 13rd resistanceThe other end ground connection.
Operational amplifier power supply is positive and negative 12V direct currents in transmitter circuit.
Embodiment
To simplify the analysis, now the various variables in circuit are defined：If first resistor
Figure 411070DEST_PATH_IMAGE008
And second resistance
Figure 635378DEST_PATH_IMAGE009
Between voltage be
Figure 696875DEST_PATH_IMAGE020
, the first operational amplifierOutput voltage be, the 3rd operational amplifier
Figure 110167DEST_PATH_IMAGE005
Output voltage is
Figure 291749DEST_PATH_IMAGE022
, four-operational amplifier
Figure 481422DEST_PATH_IMAGE007
Homophase input terminal voltage is
Figure 318928DEST_PATH_IMAGE023
, four-operational amplifier
Figure 885039DEST_PATH_IMAGE007
Anti-phase input terminal voltage is
Figure 186707DEST_PATH_IMAGE024
, four-operational amplifier
Figure 547281DEST_PATH_IMAGE007
Output voltage is
Figure 121351DEST_PATH_IMAGE025
, the tenth resistance
Figure 491153DEST_PATH_IMAGE014
With the 12nd resistanceBetween voltage be, the 12nd resistance
Figure 725322DEST_PATH_IMAGE016
With the 13rd resistance
Figure 898814DEST_PATH_IMAGE017
Between voltage be
Figure 909496DEST_PATH_IMAGE027
, transmitter output current is the 13rd resistance
Figure 877452DEST_PATH_IMAGE017
On electric current.
By
Figure 661999DEST_PATH_IMAGE008
、
Figure 373603DEST_PATH_IMAGE009
Series connection partial pressure is obtained
Figure 238791DEST_PATH_IMAGE028
Figure 377648DEST_PATH_IMAGE001
For voltage follower, therefore
Figure 898759DEST_PATH_IMAGE029
Figure 148475DEST_PATH_IMAGE003
Constitute add circuit and realize level conversion,
Figure 133749DEST_PATH_IMAGE005
For negative circuit, have
Figure 443507DEST_PATH_IMAGE030
Because transmitter input voltage
Figure 701182DEST_PATH_IMAGE031
Scope be 0-5V,, so,
Figure 594369DEST_PATH_IMAGE032
Excursion be 1.25V-6.25V.
Figure 12712DEST_PATH_IMAGE007
Constitute electric current transmission circuit.By opamp input terminal " void is disconnected " characteristic, obtain
Obtained by positive feedback branch
Figure 856537DEST_PATH_IMAGE035
Therefore
Figure 196514DEST_PATH_IMAGE036
By node current law, transmitter output currentFor
Figure 637039DEST_PATH_IMAGE038
Arrange, obtain
Because
Figure 211557DEST_PATH_IMAGE018
It is much larger than
Figure 478591DEST_PATH_IMAGE016
, above formula is approximately
Figure 677491DEST_PATH_IMAGE040
Will
Figure 267741DEST_PATH_IMAGE041
Above formula is substituted into, is obtained
Figure 526684DEST_PATH_IMAGE042
 For adjustable resistance, input voltage
Figure 18025DEST_PATH_IMAGE031
Scope is 0-5V, regulation
Figure 479093DEST_PATH_IMAGE016
For 312.5 Ω, the above-mentioned electric current transmission circuit of base in simulation software multisim, establishes simulation model, during simulation result is shown in that accompanying drawing 2, specific product are implemented, it is only necessary to one piece of four-operational amplifier integrated circuit, and a small amount of small-power resistance and a triode, it is convenient to realize, low cost.
The technological thought of above example only to illustrate the invention, it is impossible to protection scope of the present invention is limited with this, every according to technological thought proposed by the present invention, any change done on the basis of technical scheme is each fallen within the scope of the present invention.

Claims (5)

1.4-20mA current transducer circuits, it is characterized in that including input circuit, level-conversion circuit, negative circuit, electric current transmission circuit, the first operational amplifier wherein in input circuit（                                                ）Signal output part pass through 3rd resistor（
Figure 751452DEST_PATH_IMAGE002
）Connect the second operational amplifier in level-conversion circuit（
Figure 2012200604629100001DEST_PATH_IMAGE003
）Inverting input, the second operational amplifier（
Figure 809407DEST_PATH_IMAGE003
）Signal output part pass through the 6th resistance（
Figure 415969DEST_PATH_IMAGE004
）Connect the 3rd operational amplifier in negative circuit（
Figure 2012200604629100001DEST_PATH_IMAGE005
）Inverting input, the 3rd operational amplifier（
Figure 861862DEST_PATH_IMAGE005
）Signal output part pass through the 8th resistance（
Figure 350612DEST_PATH_IMAGE006
）Connect the four-operational amplifier in electric current transmission circuit（
Figure 2012200604629100001DEST_PATH_IMAGE007
）In-phase input end.
2. 4-20mA current transducers circuit according to claim 1, it is characterized in that described input circuit includes first resistor（
Figure 477837DEST_PATH_IMAGE008
）, second resistance（
Figure 2012200604629100001DEST_PATH_IMAGE009
）, the first operational amplifier（
Figure 938906DEST_PATH_IMAGE001
）, first resistor（
Figure 103171DEST_PATH_IMAGE008
）One end connection+5V power supplys, first resistor（
Figure 534677DEST_PATH_IMAGE008
）The other end connection second resistance（
Figure 13062DEST_PATH_IMAGE009
）One end, and with the first operational amplifier（）In-phase input end be connected, second resistance（
Figure 178650DEST_PATH_IMAGE009
）The other end be connected to the ground, the first operational amplifier（
Figure 579676DEST_PATH_IMAGE001
）Inverting input connection output end.
3. 4-20mA current transducers circuit according to claim 1, it is characterized in that level shifting circuit includes 3rd resistor（
Figure 924070DEST_PATH_IMAGE002
）, the 4th resistance（
Figure 608998DEST_PATH_IMAGE010
）, the 5th resistance（
Figure 2012200604629100001DEST_PATH_IMAGE011
）With the second operational amplifier（
Figure 52749DEST_PATH_IMAGE003
）, 3rd resistor（
Figure 455917DEST_PATH_IMAGE002
）One end connect the first operational amplifier（
Figure 338422DEST_PATH_IMAGE001
）Output end, 3rd resistor（
Figure 628589DEST_PATH_IMAGE002
）The other end connect the 4th resistance（
Figure 495439DEST_PATH_IMAGE010
）One end, the 5th resistance（
Figure 871056DEST_PATH_IMAGE011
）One end connect the second operational amplifier（
Figure 557253DEST_PATH_IMAGE003
）Inverting input, the 5th resistance（）The other end connection input, the 4th resistance（）The other end connect the second operational amplifier（
Figure 927557DEST_PATH_IMAGE003
）Output end, the second operational amplifier（
Figure 338816DEST_PATH_IMAGE003
）In-phase input end connection ground.
4. 4-20mA current transducers circuit according to claim 1, it is characterized in that negative circuit includes the 6th resistance（
Figure 665892DEST_PATH_IMAGE004
）, the 7th resistance（
Figure 887926DEST_PATH_IMAGE012
）With the 3rd operational amplifier（
Figure 34873DEST_PATH_IMAGE005
）, the 6th resistance（
Figure 249823DEST_PATH_IMAGE004
）One end connect the second operational amplifier（）Output end, the 6th resistance（
Figure 824341DEST_PATH_IMAGE004
）The other end connect the 3rd operational amplifier（
Figure 914044DEST_PATH_IMAGE005
）Inverting input and the 7th resistance（
Figure 480155DEST_PATH_IMAGE012
）One end, the 7th resistance（）The other end connect the 3rd operational amplifier（）Output end, the 3rd operational amplifier（
Figure 388571DEST_PATH_IMAGE005
）In-phase input end connection ground.
5. 4-20mA current transducers circuit according to claim 1, it is characterized in that electric current transmission circuit includes the 8th resistance（）, the 9th resistance（
Figure 2012200604629100001DEST_PATH_IMAGE013
）, the tenth resistance（
Figure 39181DEST_PATH_IMAGE014
）, the 11st resistance（）, the 12nd resistance（
Figure 773919DEST_PATH_IMAGE016
）, the 13rd resistance（
Figure 2012200604629100001DEST_PATH_IMAGE017
）, the 14th resistance（
Figure 569705DEST_PATH_IMAGE018
）, four-operational amplifier（
Figure 415301DEST_PATH_IMAGE007
）, NPN triode（
Figure DEST_PATH_IMAGE019
）, wherein the 8th resistance（
Figure 604144DEST_PATH_IMAGE006
）One end connect the 3rd operational amplifier（
Figure 509783DEST_PATH_IMAGE005
）Output end, the 8th resistance（
Figure 792866DEST_PATH_IMAGE006
）The other end connection four-operational amplifier（
Figure 442153DEST_PATH_IMAGE007
）In-phase input end, four-operational amplifier（）In-phase input end connect the 14th resistance（）One end, four-operational amplifier（
Figure 216577DEST_PATH_IMAGE007
）Inverting input connect the 9th resistance（
Figure 669555DEST_PATH_IMAGE013
）One end, the 9th resistance（
Figure 841779DEST_PATH_IMAGE013
）The other end connection ground, the tenth resistance（
Figure 151538DEST_PATH_IMAGE014
）One end connection four-operational amplifier（
Figure 894366DEST_PATH_IMAGE007
）Inverting input, the tenth resistance（
Figure 947773DEST_PATH_IMAGE014
）The other end connect the 12nd resistance（
Figure 977433DEST_PATH_IMAGE016
）One end, four-operational amplifier（
Figure 395776DEST_PATH_IMAGE007
）Output end connect the 11st resistance（
Figure 953796DEST_PATH_IMAGE015
）One end, the 11st resistance（
Figure 732265DEST_PATH_IMAGE015
）The other end connection transistor（
Figure 629814DEST_PATH_IMAGE019
）Base stage, transistor（）Colelctor electrode connection+5V power supplys, transistor（）Emitter stage connect the 12nd resistance（）One end, the 12nd resistance（
Figure 395328DEST_PATH_IMAGE016
）The other end and the 13rd resistance（
Figure 404741DEST_PATH_IMAGE017
）, the 14th resistance（
Figure 671774DEST_PATH_IMAGE018
）One end be connected and be connected in the output end of transmitter, the 13rd resistance（
Figure 808358DEST_PATH_IMAGE017
）The other end ground connection.
CN2012200604629U 2012-02-23 2012-02-23 4-20 ma current transmitter circuit Expired - Fee Related CN202533482U (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102590589A (en) * 2012-02-23 2012-07-18 河海大学 4-20mA current transmitter circuit
CN104320123A (en) * 2014-10-13 2015-01-28 无锡信大气象传感网科技有限公司 4-20 mA current conversion circuit
CN104482947A (en) * 2014-12-26 2015-04-01 镇江中煤电子有限公司 Mining multi-mode sensor signal transmission circuit
CN104868749A (en) * 2015-01-30 2015-08-26 宁波南车时代传感技术有限公司 Current transmitter

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102590589A (en) * 2012-02-23 2012-07-18 河海大学 4-20mA current transmitter circuit
CN102590589B (en) * 2012-02-23 2014-04-23 河海大学 4-20mA current transmitter circuit
CN104320123A (en) * 2014-10-13 2015-01-28 无锡信大气象传感网科技有限公司 4-20 mA current conversion circuit
CN104320123B (en) * 2014-10-13 2017-10-13 无锡信大气象传感网科技有限公司 A kind of 4 20mA current converter circuits
CN104482947A (en) * 2014-12-26 2015-04-01 镇江中煤电子有限公司 Mining multi-mode sensor signal transmission circuit
CN104868749A (en) * 2015-01-30 2015-08-26 宁波南车时代传感技术有限公司 Current transmitter

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Granted publication date: 20121114

Termination date: 20160223