CN2370424Y - High precision two line system digit display meter - Google Patents
High precision two line system digit display meter Download PDFInfo
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- CN2370424Y CN2370424Y CN 99231259 CN99231259U CN2370424Y CN 2370424 Y CN2370424 Y CN 2370424Y CN 99231259 CN99231259 CN 99231259 CN 99231259 U CN99231259 U CN 99231259U CN 2370424 Y CN2370424 Y CN 2370424Y
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Abstract
The utility model relates to a high precision two-wire system digit display meter, which comprises an A/D converter and a liquid crystal display. The utility model is characterized in that the utility model comprises a constant current/voltage stabilizing circuit, and a current/voltage conversion and zero adjusting circuit, wherein, the input ends of the constant current/voltage stabilizing circuit, the current/voltage conversion and zero adjusting circuit are connected with measured current signals, and the output ends are connected with the A/D converter to provide stable Vcc working voltage for the A/D converter and the liquid crystal display and provide readable voltage signals converted by the current signals for the A/D converter; an output signal wire OUT connected with the current / voltage conversion and zero adjusting circuit, and the A/D converter is taken as the reference earth.
Description
The utility model relates to a kind of high precision two-wire system digital display meter, belongs to the measurement and the display device, particularly two-wire system digital display meter of electric signal in the automatic control system.
The two-wire system instrument is used widely at automation field, and the contact between all instrument in the two-wire system system only is two leads, and these two leads are the power lead as each instrument in the system, are again signal wires.Existing two-wire system digital display meter has circuit complexity, precision is low, cost is high shortcoming.The two-wire system digital display meter of producing as the Shanghai instrument research institute only circuit (not containing A/D converter and display part) of power supply and Signal Separation part just adopts more than 30 resolution element, not only cost increases, and the instrument volume can't be dwindled, limited its usable range; The similar products of U.S. Pribusin company, 3 half liquid crystal digital display meters of two-wire system TWD-3.5 price is 190 dollars; Disclosed in Chinese patent CN2225016Y " two-wire system read out instrument " its precision is low, and the precision that reaches has only 0.3%.
The purpose of this utility model is to design a kind of cheapness, precision height, the simple and reliable high precision two-wire system digital display meter of circuit.
The purpose of this utility model is to realize like this, high precision two-wire system digital display meter, comprise A/D converter, LCD, be characterized in a constant current/mu balanced circuit, current/voltage-converted and zero-bit regulating circuit, constant current/mu balanced circuit, the signal wire INPUT of the input end of current/voltage-converted and zero-bit regulating circuit is connected with tested current signal, constant current/mu balanced circuit, the output terminal of current/voltage-converted and zero-bit regulating circuit is connected with A/D converter, output signal line OUT and current/voltage-converted and zero-bit regulating circuit, A/D converter is connected and is reference ground.
Not only circuit is simple and reliable by high precision two-wire system digital display meter that the utility model provides, and cost is low, is no more than 100 circle Renminbi, and the precision height, and precision can reach more than 0.1%.
The utility model has following accompanying drawing:
Fig. 1 is the circuit block diagram of high precision two-wire system digital display meter.
Fig. 2 is the circuit theory diagrams of high precision two-wire system digital display meter.
Embodiment of the present utility model is described with reference to the accompanying drawings, and high precision two-wire system digital display meter is made up of constant current/mu balanced circuit, current/voltage-converted and zero-bit regulating circuit, A/D converter, LCD, and its block diagram as shown in Figure 1.The signal wire INPUT of the input end of constant current/mu balanced circuit, current/voltage-converted and zero-bit regulating circuit is connected with tested current signal, the output terminal of constant current/mu balanced circuit, current/voltage-converted and zero-bit regulating circuit is connected with A/D converter, and it is with reference to ground that output signal line OUT and current/voltage-converted and zero-bit regulating circuit, A/D converter are connected.From the electric current part of INPUT input behind constant current/mu balanced circuit for A/D converter, LCD provide a stable operating voltage Vcc, and guarantee that the variation of circuit load electric current does not influence the extraction of actual signal.Current conversion of an input current part and zero-bit regulating circuit are transformed into the voltage signal that A/D converter can be read with current signal, also realize the adjusting of zero-bit simultaneously.A/D converter becomes the analog signal conversion of input digital signal and provides LCD required digital segment signal.
Circuit theory as shown in Figure 2.Constant current/mu balanced circuit is made up of current regulator diode J1, adjustable shunting Voltagre regulator S1, resistance R 7, R8, capacitor C 1, C2, C3, input end is connected with tested current signal by signal wire INPUT through R5, and the common contact of output terminal C2, R7, S1 negative terminal is connected with A/D converter operating voltage Vcc power end.Current/voltage-converted and zero-bit regulating circuit are by voltage stabilizing diode Z3, Z4, voltage stabilizing benchmark Z2, resistance R 4, R12, potentiometer W2 forms, the end of R4 is connected with the Vcc output terminal of constant current/mu balanced circuit, the negative electrode of input end Z3 and the R5 in constant current/mu balanced circuit, C1, the common contact A of J1 connects, be connected with tested current signal by signal wire INPUT through R5, output terminal R6, the Z3 anode is the contact and the R6 other end altogether, the Z4 negative electrode altogether contact respectively with the input end INH of A/D converter, COM connects, the adjustable side of W2 is connected with the input end INL of A/D converter, output signal line OUT and Z4 anode, A/D converter ground end is connected to reference to ground.When the INPUT current input signal changes between 4mA-20mA, the voltage V between A, B
ABAlso can change, current regulator diode J1 has guaranteed V thereupon
ABVariation can not cause the variation of load current.Therefore the voltage Vs on the resistance R 6 can not be subjected to the load effect on the Vcc and only be directly proportional with marking current.When the input current of INPUT end is 4mA, establish if the electric current on the J1 is 2.4mA, then the electric current on the R6 is 1.6mA, voltage is Vs=1.6 * R6 (mv).The general lower limit that requires to be shown as at this moment zero or concrete demonstration amount, no matter Vs is much, and is invariable as long as it keeps, just can eliminate it by the zero-bit regulating circuit of W2, R12, Z2 composition influences, and regulates W2 and can regulate the zero point that numeral shows easily.S1, R7, R8 have formed a mu balanced circuit in constant current/mu balanced circuit, and the voltage vcc on it is an A/D converter, and LCD provides stable operating voltage, also play the effect of Current Regulation simultaneously.When certain factor caused load current to increase, though J1 has limited the variation of electric current, the electric current on the S1 can keep total current constant thereupon reducing, and the Vcc on it does not change yet.A/D converter adopts the ICL7136A/D converter, and LCD adopts three half word LCD.
Claims (3)
1. high precision two-wire system digital display meter, comprise A/D converter, LCD, it is characterized in that having a constant current/mu balanced circuit, current/voltage-converted and zero-bit regulating circuit, the signal wire INPUT of the input end of constant current/mu balanced circuit, current/voltage-converted and zero-bit regulating circuit is connected with tested current signal, the output terminal of constant current/mu balanced circuit, current/voltage-converted and zero-bit regulating circuit is connected with A/D converter, and it is with reference to ground that output signal line OUT and current/voltage-converted and zero-bit regulating circuit, A/D converter are connected.
2. by the described high precision two-wire system of claim 1 digital display meter, it is characterized in that said constant current/mu balanced circuit is made up of current regulator diode J1, adjustable shunting Voltagre regulator S1, resistance R 7, R8, capacitor C 1, C2, C3, input end is connected with tested current signal by signal wire INPUT through R5, and the common contact of output terminal C2, R7, S1 negative terminal is connected with A/D converter operating voltage Vcc power end.
3. by the described high precision two-wire system of claim 1 digital display meter, it is characterized in that set current/voltage-converted and zero-bit regulating circuit are by voltage stabilizing diode Z3, Z4, voltage stabilizing benchmark Z2, resistance R 4, R12, potentiometer W2 forms, the end of R4 is connected with the Vcc output terminal of constant current/mu balanced circuit, the negative electrode of input end Z3 and the R5 in constant current/mu balanced circuit, C1, the common contact A of J1 connects, be connected with tested current signal by signal wire INPUT through R5, output terminal R6, the Z3 anode is the contact and the R6 other end altogether, the Z4 negative electrode altogether contact respectively with the input end INH of A/D converter, COM connects, the adjustable side of W2 is connected with the input end INL of A/D converter, output signal line OUT and Z4 anode, A/D converter ground end is connected to reference to ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99231259 CN2370424Y (en) | 1999-03-26 | 1999-03-26 | High precision two line system digit display meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99231259 CN2370424Y (en) | 1999-03-26 | 1999-03-26 | High precision two line system digit display meter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN2370424Y true CN2370424Y (en) | 2000-03-22 |
Family
ID=34020156
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 99231259 Expired - Fee Related CN2370424Y (en) | 1999-03-26 | 1999-03-26 | High precision two line system digit display meter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN2370424Y (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103558894A (en) * | 2013-11-18 | 2014-02-05 | 铜陵科达车辆装备有限责任公司 | Current signal converter circuit |
-
1999
- 1999-03-26 CN CN 99231259 patent/CN2370424Y/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103558894A (en) * | 2013-11-18 | 2014-02-05 | 铜陵科达车辆装备有限责任公司 | Current signal converter circuit |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C19 | Lapse of patent right due to non-payment of the annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |