CN100362741C - Digital type rheostat device - Google Patents
Digital type rheostat device Download PDFInfo
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- CN100362741C CN100362741C CNB2003101134700A CN200310113470A CN100362741C CN 100362741 C CN100362741 C CN 100362741C CN B2003101134700 A CNB2003101134700 A CN B2003101134700A CN 200310113470 A CN200310113470 A CN 200310113470A CN 100362741 C CN100362741 C CN 100362741C
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Abstract
The present invention provides a digital resistance variation device which comprises a first port, a second port and a current regulation circuit, wherein the current regulation circuit is connected in series between the first port and the second port. The current regulation circuit comprises a proportional control unit; the current value of the current regulation circuit is controlled by regulating the coefficient of the proportional control unit to obtain required resistance. The present invention uses an electronic circuit to simulate the external characteristics of a resistor, and the digital resistance variation device is formed. The present invention completely replaces a resistance box and a motor of the existing resistance variation device, and has the advantages of compact volume, low cost, light weight and convenient use. Because the proportional control unit adopted by the present invention controls and regulates the current value of the current module, the required resistance value can be obtained by regulating the coefficient, namely that the output resistance is digital and programmable. Thus, various instruments and meters developed and manufactured by utilizing the present invention, such as digital DC resistance boxes, hand-held process signal regulators and digital DC load devices, satisfy the requirements for miniaturization and digitization.
Description
Technical field
The present invention relates to the rheostat in a kind of electronic technology field.
Background technology
Continuous development along with electronic technology, various instrument and meters are applied to all trades and professions more and more widely, simultaneously these instrument and equipments have been proposed the requirement of digitlization, miniaturization, the calibrator (-ter) unit of especially many industrial automations, as various testers, more towards this respect fast development.The rheostat that is used at present in these instrument and meters mainly is manual rheostat and automatic rheostat.Wherein, manually rheostat comprises resistance box, and its inside is made up of many fixed resistances, obtains different resistance values by the manual adjustments resistance box.Automatically rheostat comprises motor and multiturn potentiometer, and by the rotation of motor drives multiturn potentiometer, the ad-hoc location making under the control of resistance measurement feedback circuit on the motor arrival multiturn potentiometer obtains different resistance values.Because above-mentioned two kinds of rheostats adopt heavy resistance box or motor, constituent components is more, makes that volume, weight, the cost of rheostat itself are all bigger, is difficult to accomplish microminiaturization, uses inconvenient.And above-mentioned two kinds of rheostats are to become resistance by manual or mechanical system, and automaticity is low, cause and adopt the instrument and meter equipment of these two kinds of rheostats can't reach miniaturization, digitized requirement.
Summary of the invention
The purpose of this invention is to provide the digital rheostat that a kind of volume is little, cost is low, in light weight, easy to use, make to adopt the digital DC resistance box, hand-hold type process signal prover, digital DC load device of rheostat manufacturing of the present invention and other need the instrument and meter equipment of automaticity height, microminiaturized rheostat can accomplish miniaturization, digitized requirement.
For addressing the above problem, the invention discloses a kind of digital rheostat, comprise: first port and second port, and be serially connected in current regulating circuit between described first port and described second port, the current value by regulating described current regulating circuit is to obtain required resistance.
Current regulating circuit described in the present invention comprises ratio control unit and gain first amplifying circuit and second amplifying circuit reciprocal each other that is used to control described current regulating circuit current value, and the input of described first amplifying circuit is provided with first resistance R
Stand, by described first resistance R
StandBe connected in series first port, first amplifying circuit connects ratio control unit, and described ratio control unit connects second amplifying circuit, and described second amplifying circuit is connected in series described second port.Described ratio control unit comprises digital to analog converter, and described first amplifying circuit also comprises first operational amplifier and feedback resistance, wherein, the positive terminal ground connection of first operational amplifier, negative phase end connects first resistance R
Stand, second resistance connects the negative phase end and the output of first operational amplifier, and the resistance value of second resistance and first resistance R
StandEquate, the voltage of output is as the reference voltage of digital to analog converter, described second amplifying circuit comprises second operational amplifier, the 3rd resistance, the 4th resistance, the positive terminal ground connection of described second operational amplifier, negative phase end connects the 3rd resistance, the 4th resistance is connected the negative phase end and the output of second operational amplifier, then the output resistance R of first port and second port
AB=(1-K) * R
Stand, K is the conversion coefficient of digital to analog converter, 0＜K＜1.
Described current regulating circuit comprises that the ratio control unit that is used to control described current regulating circuit current value and gain are 1 the 3rd amplifying circuit, and the 3rd amplifying circuit is provided with first resistance R
Stand, the input of described the 3rd amplifying circuit connects first port, and its output connects ratio control unit, and the output of described ratio control unit connects second port.Described ratio control unit comprises digital to analog converter, and described the 3rd amplifying circuit also comprises the 3rd operational amplifier, and wherein the negative phase end of the 3rd operational amplifier is connected with output, and positive terminal connects first resistance R
StandBack ground connection, the voltage of output are the reference voltage of digital to analog converter, the resistance value R between first port and second port
AB=(1-K) * R
Stand, K is the conversion coefficient and 0＜K＜1 of digital to analog converter.
Described current regulating circuit comprises that the ratio control unit that is used to control described current regulating circuit current value and gain are 1 the 4th amplifying circuit, and the 4th amplifying circuit is provided with first resistance R
Stand, its input connects first port, and its output connects ratio control unit, and the output of ratio control unit connects the 4th amplifying circuit, the second port ground connection.Ratio control unit comprises digital to analog converter, and the 4th amplifying circuit comprises four-operational amplifier, and wherein the negative phase end of four-operational amplifier connects its output, and the voltage of its output is the reference voltage of digital to analog converter, and positive terminal connects the first resistance V
StandAfter be connected to the output of digital to analog converter, first port connects positive terminal, then the resistance value R between first port and second port
AB=V
Stand/ (1-K), K is the conversion coefficient and 0＜K＜1 of digital to analog converter.
Described ratio control unit also comprises and the digital to analog converter microprocessor linked, regulates the resistance value of exporting by the conversion coefficient of control digital to analog converter.Described first resistance is precision resistance.
Compared with prior art, the present invention's external characteristic of electronic circuit artifical resistance, formed digital rheostat easy to use, the resistance box and the motor that have replaced existing rheostat fully, volume is small and exquisite, and cost is low, in light weight, easy to use, because the current value of the ratio control unit regulating and controlling current module that the present invention adopts, can obtain required resistance value by adjustment factor, i.e. Shu Chu resistance Digital Programmable, make and utilize the present invention to develop the various instrument and meters of manufacturing, as digital DC resistance box, hand-hold type process signal prover, digital DC load device can satisfy the digitized requirement of miniaturization.
Description of drawings
Fig. 1 is the realization schematic diagram of digital rheostat of the present invention.
Fig. 2 is the specific implementation theory diagram of digital rheostat of the present invention.
Fig. 3 is the circuit diagram of first embodiment of digital rheostat of the present invention.
Fig. 4 is the circuit diagram of second embodiment of digital rheostat of the present invention.
Fig. 5 is the circuit diagram of the 3rd embodiment of digital rheostat of the present invention.
Embodiment
See also Fig. 1, digital rheostat disclosed by the invention comprises: the first port A, the second port B and be serially connected in the first port A and the second port B between adjusting current circuit 1, according to R
AB=U/I regulates the electric current I of current circuit 1 to obtain required resistance by adjusting.
This rheostat also can comprise ratio control unit 2, and the current value of the coefficient regulating and controlling current circuit 1 by regulating ratio control unit 2 is to obtain required resistance.See also Fig. 2, ratio control unit 2 is arranged on regulates in the current circuit 1.This rheostat comprises the first port A, the second port B, regulates current module 1 and ratio control unit 2.Regulate current module 1 and be serially connected among the first port A and the second port B, the size of current that ratio control unit 2 is used to regulate current module 1 is coefficient M/one times of input voltage U, and ratio control unit 2 can be regulated its coefficient and be obtained required resistance value.
R
AB=U/I, I=U/M regulates M, and the value of I also changes, simultaneously R
ABAlso change thereupon.Be R
AB=U/I=U/ (U/M)=M, this coefficient M is the resistance of required generation, and by ratio control unit 2 control coefrficient M.
See also Fig. 3, be the embodiment circuit diagram of rheostat of the present invention.This rheostat comprises that two increase e benefit first amplifying circuit 3 reciprocal each other, second amplifying circuit 4, a digital to analog converter 5 and a microprocessor (CPU) 6.The employing gain all is two amplifying circuits 3,4 of-1 in the present embodiment.The input of first amplifying circuit 3 connects the first port A, its output linking number weighted-voltage D/A converter 5, and the voltage of output is as the reference voltage of digital to analog converter 5.The output of the input linking number weighted-voltage D/A converter 5 of second amplifying circuit 4, its output connects the second port B.First amplifying circuit 3 comprises first operational amplifier, first resistance R
StandWith the positive terminal ground connection of second resistance R, 2, the first amplifiers 3, end of oppisite phase connects first resistance R
Stand, first resistance R
StandConnect the first port A.Second resistance R 2 connects the negative phase end and the output of first operational amplifier 3 respectively.And the resistance of second resistance R 2 and first resistance R
StandResistance identical.When first resistance R
StandWhen changing, the resistance of second resistance R 2 changes accordingly, and the gain that keeps first amplifying circuit 3 is-1.Second amplifying circuit 4 comprises second operational amplifier, resistance R 3 and R4, the positive terminal ground connection of second operational amplifier, be connected with the output of digital to analog converter 5 behind the negative phase end series resistor R3, resistance R 4 is connected the negative phase end and the output of second operational amplifier, and the resistance value of resistance R 3 and resistance R 4 equates.
Be assumed to measurement at A, B two ends resistance and the voltage that applies is E, the conversion coefficient of D/A is k (0＜K＜1), and then circuit has following relational expression
V2＝-V1 (1)
V3＝K*V2 (2)
V4＝-V3＝-K*V2＝-K*(-V1)＝K*V1 (3)
V1=V4+E, V1-V4=E then, with (3) substitution V1-K*V1=E, V1=E/ (1-K) (4)
Electric current I=V1/R from the inflow of A end
Stand=E/ ((1-K) * R
Stand) (5)
Then from A, the resistance R that B sees at two ends
AB=E/I=(1-K) * R
Stand(6)
(6) formula promptly is the calculating formula of AB two ends artifical resistance.Coefficient M is (1-K) * R
StandBe required analog electrical resistance.Digital to analog converter 5 is connected with microprocessor 6, can change the resistance value of output by the adjusting conversion coefficient K.
Below be that example explanation utilizes the present invention how to obtain the high artifical resistance of precision with the high-accuracy multifunctional tester.It is 0-400 Ω, resolution that a kind of high-accuracy multifunctional tester requires the scope of the resistance of output: 0.01 Ω, error is less than 0.01%FS (i.e. 0.04 Ω).The resistance value of concrete output is 100 Ω.
A: select R
Stand, according to R
AB=E/I=(1-K) * R
Stand, R
ABScope be 0-400 Ω, then R
StandNeed to consider the error that exists in the side circuit again, so select R more than or equal to 400 Ω
StandShould be slightly larger than 400 Ω.Select the precision resistance of 450 Ω in the present embodiment, also can select the standard resistor of other resistances.
B: according to the R that chooses
StandDetermine digital to analog converter 5 with resistance resolution, because the resolution of resistance will reach 0.01 Ω, the variable quantity that is the minimum of K must reach 0.01/450=1/45000, so select the digital to analog converter 5 of 16 bit resolutions, selects for use digital to analog converter to can be LTC1595 (16bit) in the present embodiment.
C: digital to analog converter 5 is connected with microprocessor 6, determines the binary code that microprocessor 6 imports for digital to analog converter 5.According to R
AB=E/I=(1-K) * R
Stand, existing R
AB=100 Ω, R
Stand=450 Ω calculate K=1-100/450=0.777778, and then microprocessor 6 is 2 to the binary code that digital to analog converter 5 sends
16* K=50972, i.e. 0XC71C.It is than in the digital quantity V of input according to the output voltage of n figure place weighted-voltage D/A converter.＝(V
REF/2
n)*D
X，V。Be the aanalogvoltage of output, D
XBe the numeral of input, V
REFFor reference voltage obtains.Corresponding binary numeral is become aanalogvoltage, and its amplitude is by the reference voltage control of input digital to analog converter.Like this, be 100 Ω when the reading that obtains during at AB two ends measuring resistance with universal instrument or other resistance apparatus.
But, consider to be subjected to other disturbing factor influences of operational amplifier offset sum of errors when using that the actual resistance that obtains at the AB end has less error from 100 Ω.For reaching high accuracy output, also can add feedback regulation step, measure R
AB, if any error, then regulate the numerical value K of digital to analog converter by microprocessor, finally reach high accuracy output.R
ABMeasurement also very simple because flow through R
StandWith the electric current at AB two ends is the same, and as long as the characteristic of utilizing series circuit is the difference measure R
StandBoth end voltage V
StandVoltage V with the AB two ends
AB, utilize R
AB=(V
AB/ V
Stand) * R
Stand, can obtain R
AB
Embodiment 2
See also Fig. 4, be the circuit diagram of second embodiment of the invention.This adjusting current circuit 1 comprises the 3rd amplifying circuit 7, digital to analog converter 5 and microprocessor 6.Ratio control unit 2 comprises digital to analog converter 5 and microprocessor 6.The 3rd amplifying circuit 7 comprises the 3rd operational amplifier and first resistance R
Stand, wherein the negative phase end of the 3rd operational amplifier is connected with output, and positive terminal connects first resistance R
StandBack ground connection, the first port A also connects positive terminal, and the output linking number weighted-voltage D/A converter 5 of the 3rd operational amplifier, its output voltage are as the reference voltage of digital to analog converter 5, and digital to analog converter 5 connects the second port B.
Being assumed to the voltage of measuring A, B two ends resistance and applying is E, and the conversion coefficient of D/A is K (0＜k＜1), and then circuit has following relational expression:
V2＝V1 (1)
V3＝K*V2 (2)
Again because of V1=V3+E, so V1=E/ (1-K) (3)
Electric current I=V1/R from the inflow of A end
Stand=E/ (1-K)/R
Stand(4)
Then from A, the resistance R that B sees at two ends
AB=E/I=(1-K) * R
Stand(5)
(5) formula promptly is the calculating formula of artifical resistance.From (5) formula, the electric current I that the A end flows into is subjected to E control, its coefficient (1-K) * R
StandBe the resistance of required simulation.
Please refer to Fig. 5, be the circuit diagram of the present invention the 3rd embodiment.It comprises the 4th amplifying circuit 8, digital to analog converter 5 and microprocessor 6, and wherein ratio control unit is that digital to analog converter 5 and microprocessor 6, the four amplifying circuits 8 comprise the four-operational amplifier and first resistance R
Stand, wherein the negative phase end of four-operational amplifier connects its output, and positive terminal connects first resistance R
StandAfter be connected to the output of digital to analog converter 5, the first port A connects positive terminal, its output linking number weighted-voltage D/A converter 5, its output voltage is as the reference voltage of digital to analog converter 5.
Being assumed to the voltage of measuring A, B two ends resistance and applying is E, and the conversion coefficient of D/A is K (0＜k＜1), and then circuit has following relational expression:
V2＝V1＝E (1)
V3＝K*V2＝K*V1＝K*E (2)
The electric current I that flows into from A end=(V1-V3)/R
Stand=(E-K*E)/R
Stand(4)
Then from A, the resistance R that B sees at two ends
AB=E/I=R
Stand/ (1-K) (5)
(5) formula promptly is the calculating formula of artifical resistance.From (5) formula, the electric current I that the A end flows into is subjected to E control, and its coefficient W is R
Stand/ (1-K) be the resistance of required simulation.
Digital to analog converter 5 connects microprocessors 6, obtains corresponding resistance value by the corresponding binary code of input in microprocessor 6, and is better for the precision of the resistance that improves output, can adopt feedback regulation.These are open in embodiment 1, repeat no more.Digital to analog converter 5 also can select for use four to limit multiplication type digital to analog converter mutually.And digital to analog converter 5 also is not limited to be connected with microprocessor 6, reaches the conversion coefficient of control digital to analog converter.Connect switch matrix as the digital interface of digital to analog converter 5, the Kai Heguan of the switch by the control switch matrix to the different binary value of digital to analog converter 5 inputs, equally also can reach the effect that changes its conversion coefficient.
Claims (9)
1. digital rheostat is characterized in that comprising:
First port and second port, and
Be serially connected in the current regulating circuit between described first port and described second port, the current value by regulating described current regulating circuit is to obtain required resistance;
Described current regulating circuit comprises that the ratio control unit that is used to control described current regulating circuit current value and gain are-1 first amplifying circuit and second amplifying circuit, and the input of described first amplifying circuit is provided with first resistance R
Stand, by described first resistance R
StandBe connected in series first port, first amplifying circuit connects ratio control unit, and described ratio control unit connects second amplifying circuit, and described second amplifying circuit is connected in series described second port;
Described ratio control unit also comprises and the digital to analog converter microprocessor linked, regulates the resistance value of exporting by the conversion coefficient of control digital to analog converter;
Described first amplifying circuit also comprises first operational amplifier and feedback resistance, wherein, the positive terminal ground connection of first operational amplifier, negative phase end connects first resistance R
Stand, second resistance connects the negative phase end and the output of first operational amplifier, and the resistance value of second resistance and first resistance R
StandEquate, the voltage of output is as the reference voltage of digital to analog converter, described second amplifying circuit comprises second operational amplifier, the 3rd resistance, the 4th resistance, the positive terminal ground connection of described second operational amplifier, negative phase end is connected in series the output that the 3rd resistance is connected to digital to analog converter, the 4th resistance is connected the negative phase end and the output of second operational amplifier, and the resistance that the 3rd resistance is identical with the 4th resistance is identical.
2. digital rheostat as claimed in claim 1 is characterized in that, the output resistance R of first port and second port
AB=(1-K) * R
Stand, K is the conversion coefficient of digital to analog converter, 0＜K＜1.
3. digital rheostat as claimed in claim 1 or 2 is characterized in that described first resistance is precision resistance.
4. a digital rheostat is characterized in that comprising, first port and second port, and be serially connected in current regulating circuit between described first port and described second port, and the current value by regulating described current regulating circuit is to obtain required resistance;
Described current regulating circuit comprises that the ratio control unit that is used to control described current regulating circuit current value and gain are 1 the 3rd amplifying circuit, and the 3rd amplifying circuit is provided with first resistance R
Stand, the input of described the 3rd amplifying circuit connects first port, and its output connects ratio control unit, and the output of described ratio control unit connects second port;
Described ratio control unit also comprises and the digital to analog converter microprocessor linked, regulates the resistance value of exporting by the conversion coefficient of control digital to analog converter;
Described the 3rd amplifying circuit also comprises the 3rd operational amplifier, and wherein the negative phase end of the 3rd operational amplifier is connected with output, and positive terminal connects first resistance R
StandBack ground connection, the voltage of output are the reference voltage of digital to analog converter.
5. digital rheostat as claimed in claim 4 is characterized in that, the resistance value R between described first port and described second port
ABB=(1-K) * R
Stand, K is the conversion coefficient and 0＜K＜1 of digital to analog converter.
6. as claim 4 or 5 described digital rheostats, it is characterized in that described first resistance is precision resistance.
7. a digital rheostat is characterized in that comprising, first port and second port, and be serially connected in current regulating circuit between described first port and described second port, and the current value by regulating described current regulating circuit is to obtain required resistance;
Described current regulating circuit comprises that the ratio control unit that is used to control described current regulating circuit current value and gain are 1 the 4th amplifying circuit, and the 4th amplifying circuit is provided with first resistance R
StandThe 4th input amplifier connects first port, and output connects ratio control unit, and the output of ratio control unit connects the 4th amplifying circuit, the second port ground connection.
Described ratio control unit also comprises and the digital to analog converter microprocessor linked, regulates the resistance value of exporting by the conversion coefficient of control digital to analog converter;
The 4th amplifying circuit comprises four-operational amplifier, and wherein the negative phase end of four-operational amplifier connects its output, and the voltage of its output is the reference voltage of digital to analog converter, and positive terminal connects first resistance R
StandAfter be connected to the output of digital to analog converter, first port connects positive terminal.
8. digital rheostat as claimed in claim 7 is characterized in that, the resistance value R between then described first port and described second port
AB=R
Stand/ (1-K), K is the conversion coefficient and 0＜K＜1 of digital to analog converter.
9. as claim 7 or 8 described digital rheostats, it is characterized in that described first resistance is precision resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2003101134700A CN100362741C (en) | 2003-11-11 | 2003-11-11 | Digital type rheostat device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2003101134700A CN100362741C (en) | 2003-11-11 | 2003-11-11 | Digital type rheostat device |
Publications (2)
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|---|---|
| CN1545206A CN1545206A (en) | 2004-11-10 |
| CN100362741C true CN100362741C (en) | 2008-01-16 |
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|---|---|---|---|
| CNB2003101134700A Expired - Fee Related CN100362741C (en) | 2003-11-11 | 2003-11-11 | Digital type rheostat device |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104914781A (en) * | 2015-04-14 | 2015-09-16 | 常州信息职业技术学院 | Program controlled AC-DC resistance box |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101860343B (en) * | 2010-05-25 | 2012-12-05 | 北京康斯特仪表科技股份有限公司 | Digital rheostat |
| CN102914973B (en) * | 2012-10-22 | 2015-06-17 | 南京航空航天大学 | Electronic combined resistor for engine controller object in loop simulation test |
| CN103017941B (en) * | 2012-12-27 | 2014-10-22 | 北京经纬恒润科技有限公司 | Thermal-resistance simulating device |
| CN104597769A (en) * | 2013-10-31 | 2015-05-06 | 鸿富锦精密电子(天津)有限公司 | Variable-resistance device |
| CN104538136B (en) * | 2015-01-13 | 2018-08-07 | 余姚市劲仪仪表有限公司 | Numerical control rheostat |
| CN104810122A (en) * | 2015-04-14 | 2015-07-29 | 常州信息职业技术学院 | Programmable control precision resistor box |
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|---|---|---|---|---|
| US4013975A (en) * | 1975-03-31 | 1977-03-22 | Kabushikikaisha Yokogawa Denki Seisakusho | Variable resistance circuit |
| US4066914A (en) * | 1975-10-31 | 1978-01-03 | Dolby Laboratories, Inc. | Electrically variable impedance circuits |
| US4540896A (en) * | 1983-03-31 | 1985-09-10 | Tokyo Shibaura Denki Kabushiki Kaisha | Variable resistance circuit |
| CN1184320A (en) * | 1996-11-28 | 1998-06-10 | 株式会社村田制作所 | Variable resistor |
-
2003
- 2003-11-11 CN CNB2003101134700A patent/CN100362741C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4013975A (en) * | 1975-03-31 | 1977-03-22 | Kabushikikaisha Yokogawa Denki Seisakusho | Variable resistance circuit |
| US4066914A (en) * | 1975-10-31 | 1978-01-03 | Dolby Laboratories, Inc. | Electrically variable impedance circuits |
| US4540896A (en) * | 1983-03-31 | 1985-09-10 | Tokyo Shibaura Denki Kabushiki Kaisha | Variable resistance circuit |
| CN1184320A (en) * | 1996-11-28 | 1998-06-10 | 株式会社村田制作所 | Variable resistor |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104914781A (en) * | 2015-04-14 | 2015-09-16 | 常州信息职业技术学院 | Program controlled AC-DC resistance box |
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Address after: Central control science and Technology Park (hi tech Zone), No. six, No. 309, Binjiang District Road, Zhejiang, Hangzhou Patentee after: Zhongkong Technology Co., Ltd., Zhejiang Address before: No. six, No. 309, Binjiang District Road, Hangzhou, Zhejiang Patentee before: Zhejiang Supcon Technology Co., Ltd. |
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