CN104375444A - 4-20 mA current signal output circuit - Google Patents
4-20 mA current signal output circuit Download PDFInfo
- Publication number
- CN104375444A CN104375444A CN201410656547.7A CN201410656547A CN104375444A CN 104375444 A CN104375444 A CN 104375444A CN 201410656547 A CN201410656547 A CN 201410656547A CN 104375444 A CN104375444 A CN 104375444A
- Authority
- CN
- China
- Prior art keywords
- resistance
- operational amplifier
- reference voltage
- pwm signal
- current value
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
- G05B19/0423—Input/output
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/26—Pc applications
- G05B2219/2604—Test of external equipment
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Amplifiers (AREA)
Abstract
The invention relates to a 4-20 mA current signal output circuit. The 4-20 mA current signal output circuit comprises a single-chip microcomputer module, a reference voltage module and a V-I conversion module. The IO port of the single-chip microcomputer module outputs a PWM signal, the PWM signal is converted into a stable voltage value through a two-order filter circuit in the V-I conversion module, the signal value is converted into a needed current value through V-I conversion, the output current value is adjusted by changing the duty ratio of the PWM signal, the reference voltage module provides the stable reference voltage for V-I conversion in the V-I conversion module. The 4-20 mA current signal output circuit has the advantages that a very small number of components are used, the very small circuit board space is occupied, and low-cost and high-precision 4-20 mA circuit control is achieved.
Description
Technical field
The present invention relates to a kind of 4 ~ 20mA current signal output circuit, particularly relate to 4 ~ 20mA current signal output circuit that transmitter is measured.
Background technology
The various non-electrical physical quantitys that in commercial Application, transmitter is measured, as temperature, pressure, flow, humidity etc., all need its long-distance transmissions to Central Control Room, this just need convert the electric signal meeting industrial transmission standard to, as 0 ~ 5V, 0 ~ 20mA or 4 ~ 20mA, avoid occurring decaying and the problem of interference in long-distance transmissions process, wherein maximum are 4 ~ 20mA.
Existing 4 ~ 20mA current signal realizing circuit often adopts V-I change-over circuit, i.e. current/charge-voltage convertor, can be divided into integrated chip type current loop circuit and discrete component type V-I circuit for generating.Integrated chip type current loop circuit, adopt a control chip to add peripheral circuit and form, this kind of mode precision is higher, but cost is higher, and it is larger to take board area; Discrete component type V-I circuit for generating precision is not high, takies board area little.
Summary of the invention
The object of this invention is to provide 4 ~ 20mA current signal output circuit, use less element, lower cost, reach good control accuracy.
The present invention for achieving the above object, the technical scheme adopted is: 4 ~ 20mA current signal output circuit, it is characterized in that: comprise one-chip computer module, reference voltage module and V-I modular converter, the I/O port output pwm signal of described one-chip computer module, second-order filter circuit in V-I modular converter, convert stable magnitude of voltage to, required current value is converted to again through V-I, carry out regulation output current value by the dutycycle changing pwm signal, reference voltage module provides stable reference voltage for V-I in V-I modular converter changes.
The invention has the beneficial effects as follows: use little element, take very little circuit board space, achieve low cost, high-precision 4 ~ 20mA control circui.
Accompanying drawing explanation
Fig. 1 is that circuit of the present invention connects block diagram;
Fig. 2 is V-I modular converter circuit theory diagrams of the present invention.
Embodiment
For a more clear understanding of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments:
As shown in Figure 1,4 ~ 20mA current signal output circuit, comprising: one-chip computer module, reference voltage module and V-I modular converter.
One-chip computer module, by I/O port output pwm signal, converts pwm signal to voltage signal by V-I modular converter, then converts voltage signal to current signal, and reference voltage module provides reference voltage for V-I modular converter, improves control accuracy.Single-chip I/O mouth output pwm signal, regulates the dutycycle of pwm signal, can change the voltage signal that pwm signal converts to by V-I modular converter, thus convert required current signal to.
As shown in Figure 2, V-I modular converter physical circuit connects, pwm signal is by resistance R1, resistance R2 is connected with the inverting input of operational amplifier U1, one end of the one terminating resistor R2 of electric capacity C1, the other end of the one terminating resistor R2 of electric capacity C2, electric capacity C1, the ground pin of another termination operational amplifier U1 of electric capacity C2, one end of resistance R6, the emitter of triode Q1 and ground, the in-phase input end connecting resistance R3 of operational amplifier U1, one end of resistance R4, the other end output current value I-of the other end connecting resistance R6 of resistance R4, the output terminal of operational amplifier U1 connects the base stage of triode Q1 by resistance R5, the collector output current value I+ of triode Q1, the positive supply pin of operational amplifier U1 connects power Vcc.At PWM input end, the second order filter be made up of resistance R1, resistance R2, electric capacity C1 and electric capacity C2 is utilized pwm signal to be converted to stable voltage signal Vin, operational amplifier U1 is used to cushion Vin, and control NPN triode Q1, by controlling the V of triode Q1
bevoltage, can be set to required value by the electric current through pull-up resistor R6.
The tie point voltage of resistance R3 and resistance R4 is:
V
R34=（V
R6+V
ref）×R4/(R3+R4)-V
R6
Note: V
r6for the voltage at resistance R6 pull-up resistor two ends.
After circuit stability, the character according to operational amplifier:
V
in= V
R34
This example gets R3=R4:
V
in=（V
R6+V
ref）/2-V
R6=V
ref/2- V
R6/2
V
R6= V
ref-2V
in
Work as V
inwhen=0, flow through maximum current, now V
r6=V
ref, maximum current value is V
ref/ R6.
Work as V
in=V
refwhen/2, no current flows through, and selects suitable parameter just can realize output current value between 4 ~ 20mA.
One-chip computer module externally can export the pwm signal of 16, can ensure the precision of Current adjustment.Because operational amplifier input impedance is very high, substantially V can not be affected
insize, and V
refstable reference voltage is provided, the stability that circuit exports can be ensured.
According to the above description, the present invention only uses less discrete component lower cost just can realize high-precision 4 ~ 20mA electric current output function.
4 ~ 20mA current signal is a kind of conventional industrial transmission standard electric signal.Transmitter converts the measured value of physical quantity to 4 ~ 20mA current signal, is transferred to remote Central Control Room.
Claims (2)
1. 4 ~ 20mA current signal output circuit, it is characterized in that: comprise one-chip computer module, reference voltage module and V-I modular converter, the I/O port output pwm signal of described one-chip computer module, second-order filter circuit in V-I modular converter, convert stable magnitude of voltage to, be converted to required current value through V-I again, carry out regulation output current value by the dutycycle changing pwm signal, reference voltage module provides stable reference voltage for V-I in V-I modular converter changes.
2. 4 ~ 20mA current signal output circuit according to claim 1, it is characterized in that: described V-I modular converter physical circuit connection is, pwm signal is by resistance R1, resistance R2 is connected with the inverting input of operational amplifier U1, one end of the one terminating resistor R2 of electric capacity C1, the other end of the one terminating resistor R2 of electric capacity C2, electric capacity C1, the ground pin of another termination operational amplifier U1 of electric capacity C2, one end of resistance R6, the emitter of triode Q1 and ground, the in-phase input end connecting resistance R3 of operational amplifier U1, one end of resistance R4, the other end output current value I-of the other end connecting resistance R6 of resistance R4, the output terminal of operational amplifier U1 connects the base stage of triode Q1 by resistance R5, the collector output current value I+ of triode Q1, the positive supply pin of operational amplifier U1 connects power Vcc.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410656547.7A CN104375444A (en) | 2014-11-18 | 2014-11-18 | 4-20 mA current signal output circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410656547.7A CN104375444A (en) | 2014-11-18 | 2014-11-18 | 4-20 mA current signal output circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN104375444A true CN104375444A (en) | 2015-02-25 |
Family
ID=52554442
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410656547.7A Pending CN104375444A (en) | 2014-11-18 | 2014-11-18 | 4-20 mA current signal output circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN104375444A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105425846A (en) * | 2015-12-31 | 2016-03-23 | 天津宝恒流体控制设备股份有限公司 | Large-factor speed change regulating mechanism for electric actuator |
| CN110006505A (en) * | 2019-02-21 | 2019-07-12 | 杭州美仪自动化有限公司 | A kind of ultrasonic level gage and its liquid-level detecting method |
-
2014
- 2014-11-18 CN CN201410656547.7A patent/CN104375444A/en active Pending
Non-Patent Citations (3)
| Title |
|---|
| NOBERT RAUCH, 等: "将单片机PWM信号变送成工业标准电流输出4-20mA", 《传感器世界》 * |
| 林勇: "工业控制用4~20mA电流变送器", 《电子元器件应用》 * |
| 谦谦骏马: "0-5V转4-20mA proteus电路图", 《百度文库》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105425846A (en) * | 2015-12-31 | 2016-03-23 | 天津宝恒流体控制设备股份有限公司 | Large-factor speed change regulating mechanism for electric actuator |
| CN110006505A (en) * | 2019-02-21 | 2019-07-12 | 杭州美仪自动化有限公司 | A kind of ultrasonic level gage and its liquid-level detecting method |
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Legal Events
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|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20150225 |
|
| WD01 | Invention patent application deemed withdrawn after publication |