CN220105151U - Circuit for widening measuring range of digital ammeter - Google Patents
Circuit for widening measuring range of digital ammeter Download PDFInfo
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- CN220105151U CN220105151U CN202321604613.7U CN202321604613U CN220105151U CN 220105151 U CN220105151 U CN 220105151U CN 202321604613 U CN202321604613 U CN 202321604613U CN 220105151 U CN220105151 U CN 220105151U
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- 238000003466 welding Methods 0.000 claims description 8
- HPDFFVBPXCTEDN-UHFFFAOYSA-N copper manganese Chemical group [Mn].[Cu] HPDFFVBPXCTEDN-UHFFFAOYSA-N 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 description 4
- 238000005259 measurement Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
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Abstract
The utility model relates to a circuit for widening the range of a digital ammeter, which consists of a potentiometerR W Digital ammeter to be retrofitted, switch K and shunt resistorRConstructing a multi-range digital ammeter after range widening, wherein the positive electrode of the multi-range digital ammeter after range widening and the potentiometerR W Is connected with one end of the switch K, the potentiometerR W The other end of the switch K is connected with the positive electrode of the digital ammeter to be refitted, and the other end of the switch K is connected with the shunt resistorROne end of the meter is connected with the meterNegative pole of character ampere meter, negative pole of digital ampere meter to be refitted and shunt resistorRIs connected with the other end of the connecting rod. The ammeter formed by the circuit can greatly widen the measuring range of the existing digital ammeter, has the advantages of simple circuit structure, high precision, strong anti-interference capability and low cost, and solves the problems of application in the fields of digital instrument refitting, industrial automation and the like.
Description
Technical Field
The utility model relates to the fields of measuring instruments and meters and industrial automation, in particular to a circuit for widening the range of a digital ammeter with high precision.
Background
A digital ammeter is an instrument capable of measuring the magnitude of current and displaying the current, and in order to ensure the normal operation of a circuit and detect circuit errors, the current of the circuit needs to be measured. The multi-range digital ammeter generally realizes range switching by switching different sampling resistors. But in practical measurement applications we typically encounter the following: the purchased digital ammeter has only one measuring range, and the actually needed measuring current is larger than the measuring range of the purchased digital ammeter, if the purchased digital ammeter has a large measuring range again, the measuring precision is insufficient in the case of small current; if the two ammeters with large measuring range and small measuring range are purchased, on one hand, the cost is increased, and on the other hand, the instrument interface is not attractive. Therefore, the range of the existing digital ammeter is widened with high precision to meet different measurement requirements, and the digital ammeter has high practical value in the fields of power, electronics, communication, automation and the like.
The traditional circuit for widening the range of the existing digital ammeter is to realize the refitting of different ranges by connecting the existing digital ammeter and a shunt resistor in parallel. The circuit for widening the measuring range of the current digital circuit meter requires that the internal resistance and the shunt resistance of the existing digital current meter must meet a certain proportion relation, however, the internal resistance of the existing digital current meter is determined, and when the shunt resistance is smaller, the shunt resistance is difficult to adjust or select so that the internal resistance of the existing digital current meter and the internal resistance of the existing digital current meter just meet a certain proportion relation. Such as: in order to expand the range of the existing ammeter by 100 times, the internal resistance and the shunt current of the existing ammeter must satisfy 99:1, if the internal resistance of the conventional ammeter is 10 Ω, the shunt resistance should be 0.10101 Ω, and the shunt resistance of 0.10101 Ω is actually the sum of the branch line resistance, the welding point contact resistance, the on-resistance and the shunt resistance of the shunt resistor, which are all small and have large randomness, so that the size of the shunt resistance actually welded during calibration is difficult to adjust or select.
Disclosure of Invention
Aiming at the problems in the prior art, the circuit for widening the measuring range of the digital ammeter is provided, the problem that the actual welded shunt resistance is difficult to adjust or select when the calibration exists in the prior art is solved, meanwhile, the measuring range of the existing digital ammeter is reserved, and the multipurpose of one meter is realized, so that different measuring requirements of the digital ammeter in practical application are met.
The technical scheme for realizing the aim of the utility model is as follows:
a circuit for widening the range of a digital ammeter comprises a potentiometer R W The digital ammeter to be refitted, the switch K and the shunt resistor R construct a multi-range digital ammeter after the wide range, and the anode of the multi-range digital ammeter after the wide range and the potentiometer R are connected W Is connected with one end of the switch K, the potentiometer R W The other end of the switch K is connected with one end of the shunt resistor R, and the multi-range digital ammeter cathode after the range is widened is connected with the digital ammeter cathode to be modified and the other end of the shunt resistor R.
The resistance value of the shunt resistor R is R g /(n-1)，R g And n is the expansion multiple of the range of the digital ammeter to be retrofitted.
During calibration, the potentiometer R is adjusted w So that (R) wo +R g ):(R+R l +R k +R S ) 1, wherein R wo Is a potentiometer R w Output resistance R g For the internal resistance of the digital ammeter to be refitted, R l Wire resistance being the branch in which the shunt resistor R is located，R k For the on-resistance of the switch K, R S And n is the expansion multiple of the range of the digital ammeter to be refitted for the contact resistance of the welding point of the branch where the shunt resistor R is positioned.
When the switch K is opened, the range of the multi-range digital ammeter after the range widening is the same as the range of the digital ammeter to be refitted, and when the switch K is closed, the range of the multi-range digital ammeter after the range widening is n times of the range of the digital ammeter to be refitted.
The potentiometer R w A precision potentiometer of + -100 ppm/DEG C.
The shunt resistor R is a manganese copper resistor.
The switch K is a switch with an on-resistance of mΩ stage.
The utility model has the beneficial effects that:
in the technical scheme, the resistance value of the shunt resistor is not required to be regulated during calibration, and only the potentiometer R is required to be regulated w So that potentiometer R w Output resistor R wo And internal resistance R of digital ammeter to be refitted g Sum and lead resistance R of branch where shunt resistance R is located l On-resistance R of switch K k The welding point contact resistance R of the branch where the shunt resistor R is located S And the sum of the shunt resistance R meets the relation (n-1): 1, wherein n is the expansion multiple of the range of the digital ammeter to be modified.
According to the technical scheme, the measuring range of the existing digital ammeter can be greatly widened on the basis of not changing the structure of the existing digital ammeter, the precision of the digital ammeter after the expansion is the same as that of the digital ammeter to be refitted, the number of peripheral elements is small, the circuit structure is simple, the anti-interference capability is high, the cost is low, and the application problem of the ammeter in the fields of electric power, electronics, communication, automation and the like can be solved.
Drawings
FIG. 1 is a schematic circuit diagram of an embodiment;
in the figure, 1, a digital ammeter to be modified 2, and a multi-range digital ammeter after range widening.
Detailed Description
The utility model will now be described in further detail with reference to the drawings and specific examples, which are not intended to limit the utility model thereto.
Examples:
referring to FIG. 1, a circuit for widening the range of a digital ammeter is provided, which is composed of a potentiometer R W The digital ammeter 1 to be modified, the switch K and the shunt resistor R construct a multi-range digital ammeter 2 after the range is widened, and the anode of the multi-range digital ammeter 2 after the range is widened and the potentiometer R W Is connected with one end of the switch K, the potentiometer R W The other end of the switch K is connected with the positive electrode of the digital ammeter 1 to be refitted, the other end of the switch K is connected with one end of the shunt resistor R, and the negative electrode of the multi-range digital ammeter 2 after the range is widened is connected with the negative electrode of the digital ammeter 1 to be refitted and the other end of the shunt resistor R.
The resistance value of the shunt resistor R is R g /(n-1)，R g The internal resistance of the digital ammeter 1 to be modified is n which is the expansion multiple of the measuring range of the digital ammeter 1 to be modified.
During calibration, the potentiometer R is adjusted w So that (R) wo +R g ):(R+R l +R k +R S ) 1, wherein R wo Is a potentiometer R w Output resistance R g For the internal resistance of the digital ammeter 1 to be modified, R l Is the lead resistance of the branch where the shunt resistor R is located, R k For the on-resistance of the switch K, R S And n is the expansion multiple of the range of the digital ammeter 1 to be retrofitted, and is the contact resistance of the welding point of the branch where the shunt resistor R is located.
When the switch K is opened, the range of the multi-range digital ammeter 2 after the range is widened is the same as the range of the digital ammeter 1 to be refitted, and when the switch K is closed, the range of the multi-range digital ammeter 2 after the range is widened is n times of the range of the digital ammeter 1 to be refitted.
The potentiometer R w A precision potentiometer of + -100 ppm/DEG C.
The shunt resistor R is a manganese copper resistor.
The switch K is a switch with an on-resistance of mΩ stage.
The specific case is exemplified as follows:
in this example, the range of the digital ammeter 1 to be retrofitted is known to be 500 mu A, and the internal resistance is R g The range of the digital ammeter is widened to 500mA at present, and the multi-range digital ammeter 2 after the range is widened is constructed with the original range is disclosed. From example known conditions, the digital ammeter to be retrofitted can be calculated 1 scale expansion factor n=500 mA/500 μa=1000, so that the shunt resistance r=r g /(n-1)＝100/(1000-1)＝0.1001Ω。
When the switch K is closed, the lead resistance R of the branch where the shunt resistance R is located l On-resistance R of switch K k The welding point contact resistance R of the branch where the shunt resistor R is located S And shunt resistance R, although small and having a large random error, are determined after welding, assuming that R+R is measured after welding l +R k +R S = 0.1120 Ω, consisting of (R wo +R g ):(R+R l +R k +R S ) As can be seen from the relation of the formula (1) and the formula (1), the 20 omega precision adjustable potentiometer R with the temperature coefficient of +/-100 ppm/DEG C is adopted during calibration w Adjusting potentiometer R w So that it outputs a resistance R wo ＝(n-1)×(R+R l +R k +R S )-R g The digital ammeter with the measuring range of 500 mu A can be widened into the digital ammeter with the measuring range of 500mA by using the method of= (1000-1) multiplied by 0.1120 omega-100 omega = 11.888 omega.
When the switch K is opened, compared with the digital ammeter 1 to be modified, the multi-range digital ammeter 2 after the range is widened is additionally connected with a resistor of 11.888 omega in series, which is equivalent to the fact that the internal resistance of the multi-range digital ammeter 2 after the range is widened is 11.888 omega larger than the internal resistance of the digital ammeter 1 to be modified. If the current to be measured is a constant current source, the measured value of the multi-range digital ammeter 2 after the range is widened is the same as the measured value of the digital ammeter 1 to be modified, namely the range of the multi-range digital ammeter 2 after the range is widened is the same as the range of the digital ammeter 1 to be modified.
In this example, when the switch K is closed, the shunt resistor R is not required to be regulated in calibration, and only the precise adjustable potentiometer R of 20Ω is required to be regulated w So that it outputs a resistance R wo = 11.888 Ω, which can be realizedThe digital ammeter with the measuring range of 500 mu A is widened into a digital ammeter with the measuring range of 500 mA; when the switch K is opened, the range of the multi-range digital ammeter 2 after the range is widened is the same as the range of the digital ammeter 1 to be modified. When the calibration in the prior art is solved, the shunt resistor R needs to be adjusted so that R+R l +R k +R S A difficult regulation problem, exactly equal to 0.1001 omega. Since the shunt resistance R is too small, this adjustment is hardly possible in practical debugging.
Compared with the prior art, the method has the advantages that on the basis of not changing the structure of the existing digital ammeter, the measuring range of the existing digital ammeter is widened by 1000 times, the precision of the digital ammeter after the expansion is the same as that of the digital ammeter to be refitted, the number of peripheral elements is small, the circuit structure is simple, the anti-interference capability is high, the cost is low, and the problem that the ammeter is applied in the fields of electric power, electronics, communication, automation and the like can be solved.
Claims (7)
1. A circuit for widening the range of a digital ammeter is characterized in that the circuit is composed of a potentiometer R W The digital ammeter to be refitted, the switch K and the shunt resistor R construct a multi-range digital ammeter after the wide range, and the anode of the multi-range digital ammeter after the wide range and the potentiometer R are connected W Is connected with one end of the switch K, the potentiometer R W The other end of the switch K is connected with one end of the shunt resistor R, and the multi-range digital ammeter cathode after the range is widened is connected with the digital ammeter cathode to be modified and the other end of the shunt resistor R.
2. The circuit for widening the range of a digital ammeter according to claim 1, wherein the shunt resistor R has a resistance of R g /(n-1)，R g And n is the expansion multiple of the range of the digital ammeter to be retrofitted.
3. A widening of the range of a digital ammeter according to claim 1Is characterized in that the potentiometer R is adjusted during calibration w Let (R) wo +R g ):(R+R l +R k +R S ) 1, wherein R wo Is a potentiometer R w Output resistance R g For the internal resistance of the digital ammeter to be refitted, R l Is the lead resistance of the branch where the shunt resistor R is located, R k For the on-resistance of the switch K, R S And n is the expansion multiple of the range of the digital ammeter to be refitted for the contact resistance of the welding point of the branch where the shunt resistor R is positioned.
4. The circuit for widening the range of the digital ammeter according to claim 1, wherein when the switch K is opened, the range of the multi-range digital ammeter after widening the range is the same as the range of the digital ammeter to be modified, and when the switch K is closed, the range of the multi-range digital ammeter after widening the range is n times of the range of the digital ammeter to be modified.
5. A circuit for widening the range of a digital ammeter according to claim 1, wherein the potentiometer R w A precision potentiometer of + -100 ppm/DEG C.
6. The circuit for widening the range of a digital ammeter according to claim 1, wherein the shunt resistor R is a manganese-copper resistor.
7. A circuit for widening the range of a digital ammeter according to claim 1, wherein the switch K is a switch whose on-resistance is mΩ.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202321604613.7U CN220105151U (en) | 2023-06-25 | 2023-06-25 | Circuit for widening measuring range of digital ammeter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202321604613.7U CN220105151U (en) | 2023-06-25 | 2023-06-25 | Circuit for widening measuring range of digital ammeter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN220105151U true CN220105151U (en) | 2023-11-28 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202321604613.7U Active CN220105151U (en) | 2023-06-25 | 2023-06-25 | Circuit for widening measuring range of digital ammeter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN220105151U (en) |
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2023
- 2023-06-25 CN CN202321604613.7U patent/CN220105151U/en active Active
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