CN204214936U - A kind of floating ground measurement circuit - Google Patents
A kind of floating ground measurement circuit Download PDFInfo
- Publication number
- CN204214936U CN204214936U CN201420690925.9U CN201420690925U CN204214936U CN 204214936 U CN204214936 U CN 204214936U CN 201420690925 U CN201420690925 U CN 201420690925U CN 204214936 U CN204214936 U CN 204214936U
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- China
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- pin
- resistance
- operational amplifier
- power supply
- circuit
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Abstract
The utility model relates to a kind of floating ground measurement circuit.Tested two-wire system transducer is connected with oscillograph by optical coupling isolation circuit, and tested two-wire system transducer is by reometer A and resistance R
sbe connected with system power supply, optical coupling isolation circuit, oscillograph are connected with system power supply respectively; Optical coupling isolation circuit comprises subtraction circuit, voltage feedback loop, voltage follower circuit and light-coupled isolation chip U3; System power supply comprises direct supply I, direct supply II, AC power.In terms of existing technologies, by optical coupling isolation circuit, tested two-wire system transducer and oscillograph and power supply thereof are isolated, make two-wire system transducer not by the impact coming from oscillograph and power supply noise thereof; By controlling the parameter of optical coupling isolation circuit, V can be made
oUT=V
iN, complete the voltage measurement that measured point is held relative to COM accurately; Meanwhile, ensure that the security of operation when floating ground measurement, be easy to realize, cost is lower.
Description
Technical field
The utility model relates to integrated circuit fields of measurement, particularly a kind of floating ground measurement circuit.
Background technology
Two-wire system transducer is widespread use in the industry.Physical quantity is converted to 4 ~ 20mA electric current and exports by general two-wire system transducer, and 4 ~ 20mA electric current is originally powered as transmitter simultaneously.But due to the existence of conductor resistance, the reference ground level of two-wire system transducer is also not equal to the ground level of power-supply system, and this brings difficulty to the measurement of two-wire system transducer.
All voltage measurements are all difference measurements, and voltage measurement divides measures and floating ground measurement (measurement of non-reference ground level) two classes with reference to ground level.During voltage measurement; most of traditional oscillograph is received " signal reference " connecting terminals on protective grounding system; all like this signals being applied to oscillographic signal or oscillograph and providing all can have a points of common connection; this points of common connection is oscillograph cabinet normally; by the Article 3 line ground connection in AC power-supply unit power lead, remain on (or close) zero volt.Traditional passive should do not used during floating ground measurement to pop one's head in and directly carrying out floating ground measurement with reference on the oscillograph of ground level, depending on flowing through the amount of current of reference leads, traditional passive probe can start heating, and when electric current is enough high, it can melt disconnection.Floating ground measurement technology has Isolation input oscillograph, difference detector, voltage spacer assembly etc.
Summary of the invention
In view of the situation of prior art, the utility model provides a kind of floating ground measurement circuit, makes the floating neutral system of tested two-wire system transducer not by the impact of the earth electrical property, improves the accuracy and the security that use oscillograph to carry out floating ground measurement.
The utility model is for realizing above-mentioned technical purpose, the technical scheme adopted is: a kind of floating ground measurement circuit, comprise two-wire system transducer, oscillograph, system power supply, it is characterized in that: also comprise optical coupling isolation circuit, described tested two-wire system transducer is connected with oscillograph by described optical coupling isolation circuit, and tested two-wire system transducer is by reometer A and resistance R
sbe connected with system power supply, described optical coupling isolation circuit, oscillograph are connected with system power supply respectively; Described optical coupling isolation circuit comprises subtraction circuit, voltage feedback loop, voltage follower circuit and light-coupled isolation chip U3; Described system power supply comprises direct supply I, direct supply II, AC power;
Described voltage follower circuit comprises adjustable resistance R7 and operational amplifier U2, described voltage feedback loop comprises resistance R5, resistance R6, electric capacity C1, described subtraction circuit comprises resistance R1, R2, R3, R4 and operational amplifier U1, physical circuit connects: resistance R1 mono-tunnel connects 2 pin of operational amplifier U1, resistance R2 of separately leading up to connects 1 pin and 5 pin of operational amplifier U1, resistance R3 mono-tunnel connects 3 pin of operational amplifier U1, resistance R4 of separately leading up to connects 4 pin and the reference ground of operational amplifier U1, the 6 pin connecting resistance R5 of operational amplifier U1, one end of electric capacity C1 and 4 pin of light-coupled isolation chip U3, another termination of resistance R5 is with reference to ground, 7 pin of operational amplifier U1 connect the electric capacity C1 other end, one end of resistance R6, 8 pin of operational amplifier U1 meet power supply V1+, 1 pin of light-coupled isolation chip U3 connects with reference to ground, the other end of 2 pin connecting resistance R6, 3 pin meet power supply V1+, 6 pin meet power supply V2+, 5 pin connect adjustable resistance R7 one end, 3 pin of operational amplifier U2, 4 pin of another termination operational amplifier of adjustable resistance R7 U2 and circuit ground, 1 pin of operational amplifier U2, 2 pin are for exporting V
oUT, 8 pin meet power supply V2+,
The model of described operational amplifier U1, operational amplifier U2 is OPA2180, and light-coupled isolation chip U3 model is TIL300.
The utility model has the following advantages: the utility model in terms of existing technologies, by optical coupling isolation circuit, tested two-wire system transducer and oscillograph and power supply thereof are isolated, make two-wire system transducer not by the impact coming from oscillograph and power supply noise thereof; By controlling the parameter of optical coupling isolation circuit, V can be made
oUT=V
iN, complete the voltage measurement that measured point is held relative to COM accurately; Meanwhile, the utility model ensure that the security of operation when floating ground measurement, is easy to realize, and cost is lower.
Accompanying drawing explanation
Fig. 1 is that the utility model slowdown monitoring circuit connects block diagram;
Fig. 2 is circuit theory diagrams of the present utility model.
Embodiment
Below in conjunction with the accompanying drawings and the specific embodiments the current measurement circuit that the utility model provides is described in further detail.
As shown in Figure 1 and Figure 2, a kind of floating ground measurement circuit, comprises two-wire system transducer, oscillograph, system power supply, also comprises optical coupling isolation circuit, tested two-wire system transducer is connected with oscillograph by described optical coupling isolation circuit, and tested two-wire system transducer is by reometer A and resistance R
sbe connected with system power supply, optical coupling isolation circuit, oscillograph are connected with system power supply respectively.
Optical coupling isolation circuit comprises subtraction circuit, voltage feedback loop, voltage follower circuit and light-coupled isolation chip U3; System power supply comprises direct supply I, direct supply II, AC power.
Physical circuit connects: voltage follower circuit comprises adjustable resistance R7 and operational amplifier U2, voltage feedback loop comprises resistance R5, resistance R6, electric capacity C1, subtraction circuit comprises resistance R1, R2, R3, R4 and operational amplifier U1, physical circuit connects: resistance R1 mono-tunnel connects 2 pin of operational amplifier U1, resistance R2 of separately leading up to connects 1 pin and 5 pin of operational amplifier U1, resistance R3 mono-tunnel connects 3 pin of operational amplifier U1, resistance R4 of separately leading up to connects 4 pin and the reference ground of operational amplifier U1, the 6 pin connecting resistance R5 of operational amplifier U1, one end of electric capacity C1 and 4 pin of light-coupled isolation chip U3, another termination of resistance R5 is with reference to ground, 7 pin of operational amplifier U1 connect the electric capacity C1 other end, one end of resistance R6, 8 pin of operational amplifier U1 meet power supply V1+, 1 pin of light-coupled isolation chip U3 connects with reference to ground, the other end of 2 pin connecting resistance R6, 3 pin meet power supply V1+, 6 pin meet power supply V2+, 5 pin connect adjustable resistance R7 one end, 3 pin of operational amplifier U2, 4 pin of another termination operational amplifier of adjustable resistance R7 U2 and circuit ground, 1 pin of operational amplifier U2, 2 pin are for exporting V
oUT, 8 pin meet power supply V2+.
The model of operational amplifier U1, operational amplifier U2 is OPA2180, and light-coupled isolation chip U3 model is TIL300.
Adjustable resistance R7 is accurate adjustable resistance, and its maximum value is 1.5 times of resistance R5.
Resistance R1, R2, R3, R4 meet R1=R2, R3=R4.
The ceiling voltage that direct supply I and direct supply II provides is 48V, and AC power provides 220V alternating current.In practical application, direct supply I and direct supply II can select Switching Power Supply.
Due to resistance R in practical application
sexistence, V
cOMbe not equal to V
1-, if what need to measure is the voltage that the measured point voltage of tested two-wire system transducer hold relative to COM, if do not use isolation, when directly using oscillograph to measure, easily tested two-wire system transducer is introduced in outside interference greatly; If directly use oscillograph to carry out floating ground measurement (namely ground wire is not connected with the earth), likely damage circuit during measurement or affect personal safety.What the utility model employing optical coupling isolation circuit was easy solves this problem.
The input end of subtraction circuit connects COM end and the measured point of tested two-wire system transducer, the output V of subtraction circuit respectively
oUT'=(R4/R3) * (V
iN-V
cOM); And V
iN-V
cOMbe the voltage needing the measured point voltage of the tested two-wire system transducer measured to hold relative to COM, regulate respective resistivity values to make V
oUT'=V
iN-V
cOM.
The effect of backfeed loop is the brightness stability keeping light emitting diode in optical coupling isolation circuit, and the driving force that follower U2 makes Vo hold is strengthened; The output V that optical coupling isolation circuit is final
oUT≈ V
oUT', i.e. V
oUT≈ V
iN-V
cOM.By regulating the resistance of adjustable resistance R7, V can be made
oUT=V
iN-V
cOM.
Operational amplifier U1, U2 can be realized by two-way operational amplifier OPA2180, and U3 is realized by light-coupled isolation chip TIL300; Direct supply can adopt 24V Switching Power Supply; By regulating the above circuit parameter, make the output V of optical coupling isolation circuit
oUTthe voltage that the measured point voltage equaling tested two-wire system transducer is held relative to COM, oscillograph can measure this magnitude of voltage accurately, can also measure the parameter such as respective waveforms and time.
Measuring principle
In Fig. 1, two-wire system transducer is tested instrument, and COM end is the datum (floating ground) of two-wire system transducer, needs to measure the voltage held relative to COM measured point.An input end V of optical coupling isolation circuit
cOMconnect the COM end of two-wire system transducer, another input end V of optical coupling isolation circuit
iNconnect the measured point of two-wire system transducer.Direct supply I is that two-wire system transducer is powered, and is also the energize portions of optical coupling isolation circuit near two-wire system transducer, as shown in figure V1+, V1-.The output terminal V of optical coupling isolation circuit
oUTconnect oscillographic test point CH, AC power is that oscillograph is powered, and direct supply II is the close oscillographic energize portions of optical coupling isolation circuit, as shown in figure V2+, V2-.The V2-end of direct supply II and the GND(the earth of AC power) be connected.
During two-wire system transducer work, need the voltage relative to COM end measuring measured point, if directly use oscilloscope measurement, oscillographic GND end can introduce the interference coming from the earth, affects the accuracy of the measured point voltage measured.And optical coupling isolation circuit can make output voltage equal with the voltage of measured point, i.e. V
oUT=V
iN, and the use of light-coupled isolation chip, two-wire system transducer is kept apart, not by noise with the earth.After application optical coupling isolation circuit, due to V
oUT=V
iN, V measured by oscillograph
oUTbe the voltage that measured point is held relative to COM.
Claims (1)
1. a floating ground measurement circuit, comprise two-wire system transducer, oscillograph, system power supply, it is characterized in that: also comprise optical coupling isolation circuit, described tested two-wire system transducer is connected with oscillograph by described optical coupling isolation circuit, and tested two-wire system transducer is by reometer A and resistance R
sbe connected with system power supply, described optical coupling isolation circuit, oscillograph are connected with system power supply respectively; Described optical coupling isolation circuit comprises subtraction circuit, voltage feedback loop, voltage follower circuit and light-coupled isolation chip U3; Described system power supply comprises direct supply I, direct supply II, AC power;
Described voltage follower circuit comprises adjustable resistance R7 and operational amplifier U2, described voltage feedback loop comprises resistance R5, resistance R6, electric capacity C1, described subtraction circuit comprises resistance R1, R2, R3, R4 and operational amplifier U1, physical circuit connects: resistance R1 mono-tunnel connects 2 pin of operational amplifier U1, resistance R2 of separately leading up to connects 1 pin and 5 pin of operational amplifier U1, resistance R3 mono-tunnel connects 3 pin of operational amplifier U1, resistance R4 of separately leading up to connects 4 pin and the reference ground of operational amplifier U1, the 6 pin connecting resistance R5 of operational amplifier U1, one end of electric capacity C1 and 4 pin of light-coupled isolation chip U3, another termination of resistance R5 is with reference to ground, 7 pin of operational amplifier U1 connect the electric capacity C1 other end, one end of resistance R6, 8 pin of operational amplifier U1 meet power supply V1+, 1 pin of light-coupled isolation chip U3 connects with reference to ground, the other end of 2 pin connecting resistance R6, 3 pin meet power supply V1+, 6 pin meet power supply V2+, 5 pin connect adjustable resistance R7 one end, 3 pin of operational amplifier U2, 4 pin of another termination operational amplifier of adjustable resistance R7 U2 and circuit ground, 1 pin of operational amplifier U2, 2 pin are for exporting V
oUT, 8 pin meet power supply V2+,
The model of described operational amplifier U1, operational amplifier U2 is OPA2180, and light-coupled isolation chip U3 model is TIL300.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420690925.9U CN204214936U (en) | 2014-11-18 | 2014-11-18 | A kind of floating ground measurement circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420690925.9U CN204214936U (en) | 2014-11-18 | 2014-11-18 | A kind of floating ground measurement circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN204214936U true CN204214936U (en) | 2015-03-18 |
Family
ID=52983598
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201420690925.9U Withdrawn - After Issue CN204214936U (en) | 2014-11-18 | 2014-11-18 | A kind of floating ground measurement circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN204214936U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104374985A (en) * | 2014-11-18 | 2015-02-25 | 中环天仪股份有限公司 | Floating ground measuring circuit for two-wire transmitter |
-
2014
- 2014-11-18 CN CN201420690925.9U patent/CN204214936U/en not_active Withdrawn - After Issue
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104374985A (en) * | 2014-11-18 | 2015-02-25 | 中环天仪股份有限公司 | Floating ground measuring circuit for two-wire transmitter |
| CN104374985B (en) * | 2014-11-18 | 2017-03-01 | 中环天仪股份有限公司 | A kind of floating ground measurement circuit for two-wire system transducer |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| AV01 | Patent right actively abandoned | ||
| AV01 | Patent right actively abandoned |
Granted publication date: 20150318 Effective date of abandoning: 20171114 |