CN214585670U - High-impedance pointer type direct current voltmeter - Google Patents
High-impedance pointer type direct current voltmeter Download PDFInfo
- Publication number
- CN214585670U CN214585670U CN202120538362.1U CN202120538362U CN214585670U CN 214585670 U CN214585670 U CN 214585670U CN 202120538362 U CN202120538362 U CN 202120538362U CN 214585670 U CN214585670 U CN 214585670U
- Authority
- CN
- China
- Prior art keywords
- circuit
- resistor
- operational amplifier
- voltage
- voltmeter
- 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.)
- Expired - Fee Related
Links
- 239000003990 capacitor Substances 0.000 claims abstract description 8
- 238000006243 chemical reaction Methods 0.000 claims abstract description 4
- 230000001105 regulatory effect Effects 0.000 claims abstract description 4
- 230000003068 static effect Effects 0.000 claims abstract description 3
- 230000003321 amplification Effects 0.000 description 7
- 238000003199 nucleic acid amplification method Methods 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 230000008569 process Effects 0.000 description 3
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000003393 splenic effect Effects 0.000 description 1
Images
Landscapes
- Measurement Of Current Or Voltage (AREA)
Abstract
The utility model discloses a high impedance pointer type direct current voltmeter, which comprises a resistance network voltage divider circuit, a range conversion switch circuit, a limiting circuit, a filter circuit, an in-phase proportion operation circuit, an input offset voltage adjusting circuit, a range full scale deflection adjusting circuit, an ammeter circuit and a direct current supply circuit; resistors R1-R5 are sequentially connected in series to form a resistor network voltage divider circuit, and a moving contact of the range selector S is connected with the voltage divider circuit; the operational amplifier A1 and the resistor R7 form an in-phase proportional operation circuit, a static contact of the range selector S is connected with the pin 3 of the A1 through the resistor R6, and the pin 3 of the operational amplifier A1 is connected with a working ground through the amplitude limiting circuit D1 and the filter capacitor C1; the resistor R8 and the potentiometer P1 form an input offset voltage adjusting circuit; the potentiometer P2 forms a full-scale deflection regulating circuit, the pin 6 of the operational amplifier A1 is connected with a working ground through a resistor R9, the potentiometer P2 and a current meter G in sequence, and the current meter G displays the voltage to be measured.
Description
Technical Field
The utility model relates to an improve the technique that direct current voltmeter detected the precision, especially one kind utilizes the input resistance that ideal fortune was put to be this characteristics of infinity, improves ordinary pointer voltmeter, can realize the high impedance input of pointer voltmeter, successfully accomplishes the design of an ideal direct current voltmeter, improves measurement accuracy greatly
Background
Usually, the voltmeter can be modified by a microammeter (a kind of ammeter) or a sensitive ammeter, and under the condition that the full bias current and the internal resistance of the microammeter are constant, the voltage which can be borne by two ends of the microammeter is increased as long as a sufficiently large resistor is connected in series.
If the full bias current is I, the internal resistance of the microammeter is R, and the resistance value of the series resistor is R, the range of the modified voltmeter is I (R + R), and the larger the R, the larger the range is, which can be considered as one of the reasons why the voltmeter is connected with a large resistor in series.
When the voltmeter works, the voltmeter is connected in parallel to the circuit to be tested or the resistor, the voltage at the two ends of the voltmeter and the voltage at the two ends of the circuit are equal, if the resistor of the voltmeter is not negligible, the total resistance value of the parallel circuit formed by the voltmeter and the resistor to be tested is equal to
WhereinR ALL The resistance is the parallel resistance formed by the internal resistance of the voltage meter and the resistance of the circuit to be measured,R TARGET indicating the resistance, R, of the circuit to be testedVRefers to the internal resistance of the voltmeter.
A1 can be considered to be greater than or equal to zero when and only when the internal resistance of the voltmeter is infinitely largeR V If =0, the resistance value of the parallel circuit is considered to be the resistance value of the resistor to be tested, that is, the current passing through the voltmeter is considered to be 0, and the two ends of the voltmeter are considered not to participate in the circuit. Therefore, in order to accurately measure the circuit voltage, the voltmeter must have a very large resistance, otherwise it is not negligible, and the measured value is inaccurate.
The voltmeter is divided into a pointer type voltmeter and a digital voltmeter, the internal resistance of the pointer type direct current voltmeter is small and generally below 10 megaohms, the internal resistance of the pointer type direct current voltmeter is related to the measuring range, the internal resistance is larger when the voltage is higher, even some meters only have thousands of ohms or dozens of kiloohms, and the influence on a measuring loop is large. The digital voltmeter has large internal resistance, generally above 100 megaohms, due to the input end being provided with an ADC (analog-to-digital conversion) converter, and thus has small influence on a measurement loop.
It is known that a pointer voltmeter uses a sensitive magnetoelectric dc ammeter (microammeter) as a meter head, when a small current passes through the meter head, a current indication is provided, but the meter head cannot pass a large current, so that resistors connected in parallel and in series on the meter head must be shunted or stepped down, and these resistors connected in series or in parallel are called sampling resistors, thereby measuring the voltage in the circuit.
The method is that the voltage signal obtained by the voltage divider resistance of the pointer type voltmeter is processed by an in-phase proportional amplifying circuit with the amplification factor of 1, and the in-phase proportional operation circuit introduces the voltage series negative feedback, so the input resistance is considered to be infinite, and the output resistance is 0.
The circuit output resistance is 0, has constant voltage characteristic, is equivalent to an ideal voltage source, and after the load is loaded, the circuit operation relation is unchanged, namely the internal resistance of the voltmeter head has no relation with the ideal voltage source, so that the design of an ideal direct current voltmeter is successfully completed.
Disclosure of Invention
The utility model aims to solve the technical problem that a technique of pointer voltmeter of simple structure, low in cost, use reliable higher accuracy is provided.
In order to achieve the above object, the utility model provides a high impedance pointer-type direct current voltmeter, it includes resistance network voltage divider circuit, range change over switch circuit, amplitude limiting circuit, filter circuit, cophase proportion operation circuit, input offset voltage adjusting circuit, range full scale deflection regulating circuit, galvanometer circuit and DC supply circuit. Resistors R1, R2, R3, R4 and R5 are sequentially connected in series to form the resistor network voltage divider circuit, the voltage divider circuit is bridged at two ends of a voltage to be measured, a range selector S forms the range change-over switch circuit, a 1V gear movable contact of the range selector S is connected with the upper end of a resistor R1, a 10V gear movable contact of the range selector S is connected with the connection point of resistors R2 and R3, and a 100V gear movable contact of the range selector S is connected with the connection point of resistors R4 and R5; the operational amplifier A1 and the resistor R7 form the in-phase proportional operation circuit, a static contact of the range selector S is connected with the in-phase input end of the operational amplifier A1 through an input resistor R6, the diode D1 forms the amplitude limiting circuit, the electrolytic capacitor C1 forms the filter circuit, the in-phase input end of the operational amplifier A1 is connected with a working ground through a reversely connected diode D1, and the in-phase input end of the operational amplifier A1 is connected with the working ground through a positively connected capacitor C1; the resistor R8 and the potentiometer P1 form the input offset voltage adjusting circuit, the potentiometer P1 is bridged between a pin 1 and a pin 5 of the operational amplifier A1, and the sliding end of the potentiometer P1 is connected with the working ground through the resistor R8; the potentiometer P2 forms the full-scale deflection regulating circuit, the galvanometer G forms the galvanometer circuit, the output end of the operational amplifier A1 is connected with a working ground through the resistor R9, the potentiometer P2 and the galvanometer G in sequence, and the negative end of the galvanometer G is connected with the working ground; the +/-12V power supply, the resistors R10 and R11 and the electrolytic capacitors C2 and C3 form the direct current power supply circuit.
In the in-phase proportional operation circuit, the output end of the operational amplifier A1 is connected with the inverting input end of the operational amplifier A1 through a resistor R7.
Drawings
Fig. 1, 2, 3 and 4 are included to provide a further understanding of the present invention and form a part of the present application, and fig. 1 is an inverse proportion arithmetic circuit; FIG. 2 is an in-phase proportional arithmetic circuit; FIG. 3 is a high impedance DC voltmeter circuit based on an in-phase proportional arithmetic circuit; FIG. 4 is a schematic diagram of a full scale calibration of a voltmeter.
Detailed Description
Inverse proportion operation circuit and in-phase proportion operation circuit based on ideal operational amplifier
The characteristics of an ideal operational amplifier (sometimes abbreviated as an op-amp) are as follows: (1) very large input resistance: high input impedance, the current flowing into the input end is close to 0, the signal source current is hardly used, and the voltage control characteristic is close to, thereby deriving a 'virtual break' conceptNamely, the input current of the ideal operational amplifier is equal to zero,
。
(2) extremely small output resistance: the load-free power supply has the characteristics of no load selection (within the load capacity) and adaptability to any load, and the impedance of a rear-stage load circuit does not influence the output voltage.
(3) Infinite voltage amplification (up to millions or tens of millions), which determines: under certain supply voltage conditions, the amplifier can only work in a closed loop (negative feedback) mode, and the actual amplification factor is limited; the open loop mode is the comparator state, and the output is a high level and a low level two-state. In closed loop (limited amplification factor) state, the splenic property of amplifier is to compare the electric potential of two input ends randomly, when they are not equal, the output stage can make regulation action in time, and the final purpose of amplification is to make the electric potentials of two input ends equal (their difference is 0V), so that the "virtual short" concept can be derived, i.e. it can make the difference be 0V
。
The "virtual short" and "virtual break" are two important conclusions for analyzing the ideal op-amp operation in the linear region.
Inverse proportional operation circuit
The inverse proportional operation circuit is shown in FIG. 1, which is a typical voltage parallel negative feedback circuit, the input voltageu I The output voltage is applied to the inverting input end of the integrated operational amplifier through the resistor Ru O And inputu I And reversing.
The relationship between the output voltage and the input voltage is
Output voltageu O And inputu I Proportional relation, proportionality coefficient is-RfR, minus signu O Andu I in contrast, the scaling factor may have any value greater than, equal to, or less than 1.
An output resistance of Ro=0, the operational relationship is not changed after the circuit is loaded, and the input resistance R isi= R, it can be seen that although the input resistance of an ideal operational amplifier is infinite, the input resistance of the inverse proportion operation circuit is not large because the circuit introduces negative feedback in parallel.
In-phase proportional operation circuit
The in-phase proportional operation circuit is shown in fig. 2, the circuit introduces voltage series negative feedback, so that the input resistance is considered to be infinite, the output resistance is 0, and even if the influence of the integrated operational amplifier parameters is considered, the input resistance can reach 109Omega or more.
According to the concept of 'virtual break' and 'virtual short', the net input voltage of the integrated operational amplifier is zero, i.e. uP=uO=uIThe integrated operational amplifier is illustrated with a common mode input voltage.
The relationship between the output voltage and the input voltage is
The above formula shows uOAnd uIIn phase, and uOGreater than uI。
It should be noted that although the in-phase proportional operational circuit has the advantages of high input resistance and low output resistance, since the integrated operational amplifier has a common-mode input, the integrated operational amplifier with high common-mode rejection ratio should be selected to improve the operational accuracy, and from another point of view, when performing error analysis on the circuit, special attention should be paid to the influence of the common-mode signal.
High-impedance direct-current voltmeter based on in-phase proportional operation circuit
The high input impedance operational amplifier CA3140 is a BiMOS high voltage operational amplifier developed by radio corporation in America on an integrated chip, the CA3140A and CA3140BiMOS series operational amplifier, and the transistor input circuit in the grid (on PMOS) of the function protection MOSFET provide very high input impedance, extremely low input current and high speed performance, and it combines the advantages of piezoelectric PMOS transistor technology and high voltage double-pass transistor.
The operational power supply voltage is from 4V to 36V (whether single or double power supply), the piezoelectric PMOS transistor process and the high-voltage double-pass transistor are combined, and the CMOS transistor is a complementary symmetrical metal oxide semiconductor and belongs to an operational amplifier circuit with excellent performance.
According to the above description, the input impedance of the inverse proportion operation circuit is relatively small, while the input impedance of the in-phase proportion operation circuit is very high, and the application of the in-phase proportion operation circuit to a common pointer type direct current voltmeter circuit is a very good choice, and the circuit is shown in fig. 3.
It can be seen that the voltmeter circuit comprises a resistor network voltage divider circuit, a range change-over switch circuit, a limiting circuit, a filter circuit, an in-phase proportional operation circuit, an input offset voltage adjusting circuit, a range full-scale deflection adjusting circuit, an ammeter circuit and a direct current power supply circuit.
Voltage divider and range switch
The voltage divider is a series resistor used when the voltmeter expands the measuring range, a slide rheostat can be used as the voltage divider, a fixed resistor combination can also be used as the voltage divider, and R is utilized in figure 31、R2、R3、R4、R5The resistor network forms a voltage divider circuit.
The switch S is a range selector, the voltmeter is designed with three stages of 1V, 10V and 100V to be selectable, the resistance voltage divider is matched with the range selector S, a measured value can be converted into a small direct current value suitable for meter head measurement, and the input voltage to be measured can be limited not to exceed the voltage born by the operational amplifier input end, so that the meter head can be further amplified for measurement.
The input impedance of the voltmeter can only reach around 10M Ω due to the resistance limitation of the voltage divider, but it is still satisfactory that the input impedance of the operational amplifier CA3140 itself is 1.5 × 1012Ω 。
Input voltage value amplitude limiting realized by reverse connection of diode to ground
The power supply voltage of the operational amplifier CA3140 can be supplied by a double power supply of +/-2 to +/-18V or a single power supply of +30V, and the input voltage of the operational amplifier is generally lower than the power supply voltage, so that an amplitude limiting circuit is needed to ensure the safety of a voltmeter.
IN4148 is a switching diode with a relatively high characteristic frequency, which has several common functions: 1) high-frequency small current rectification is mostly applied to a switching power supply; 2) the current guide is applied to a logic circuit and prevents the signal current from flowing in an inverted state; 3) the amplitude limiting is applied to some measuring instruments to limit the input voltage not to exceed the voltage which can be born by the IC input end; 4) the voltage stabilization, 4148, with an inverse breakdown voltage of 30V, can be used to replace a voltage regulator tube and applied to occasions with appropriate voltage stabilization value and low precision requirement.
Switch diode D in FIG. 31The model is IN4148 which is connected between the non-inverting input terminal of the operational amplifier and the operating ground IN reverse, and functions as a limiter, if the measured voltage after passing through the voltage divider or the non-inverting input terminal voltage of the amplifier exceeds 30V, the diode 4148 breaks down IN reverse direction and short-circuits to ground, preventing the amplifier from being damaged.
Electrolytic capacitor C1The first function of the operational amplifier is filtering to make the input voltage of the operational amplifier be a stable direct current voltage, and the second function is that the operational amplifier is connected with the reverse switch diode 4148 in parallel just like being connected with a real voltage stabilizing diode in parallel, so as to realize the voltage stabilizing function or the amplitude limiting function.
In-phase proportional operation circuit
Operational amplifier A1(CA 3140) the output terminal passes through a resistor R7To A1Negative feedback is introduced into the inverting input end, and the signal to be measured passes through an input resistor R6Acting on the non-inverting input terminal, the circuit introduces voltage series negative feedback, so the input resistance of the amplifier is considered to be infinite, the output resistance is zero, it is noted that the non-inverting proportional operational circuit shown in fig. 3 is slightly different from that shown in fig. 2, i.e. the inverting terminal ground resistance R in formula (1) is deleted in fig. 3, which is equivalent to infinite resistance, so the output of the non-inverting proportional amplifier shown in fig. 3u A1-6(operational amplifier A)16 pin outputEnd) is
Whereinu IThe voltage to be measured is the signal voltage after passing through the voltage divider and the range switch S, namely the main contact voltage of the band switch S.
It can be seen that since all the output voltages of the operational amplifier are fed back to the inverting input terminal, the in-phase proportional operation circuit becomes a voltage follower, so that the relationship between the output voltage and the input voltage is equal, i.e. the voltage amplification factor is "1".
Because the voltage amplification factor is 1, the operational amplifier is transparent as if the operational amplifier does not exist between the meter head and the voltage divider, but the circuit also introduces voltage series negative feedback, the input resistance is also infinite, and the output resistance is also zero, which is extremely beneficial to the accurate measurement of the direct current voltmeter.
Operational amplifier A1An input offset voltage adjusting pin is arranged between the pin 1 and the pin 5, the output zero setting of the operational amplifier is realized through an external potentiometer or a resistor, and the specific operation is described below.
Meter head circuit
The meter head is a part which is shared by the ammeter and the voltmeter, is equivalent to a small ammeter, but can pass through the ammeter with small rated current, so that the ammeter can not be used independently, and is connected with a resistor with large resistance in series to form the voltmeter, and is connected with a resistor with small resistance in series to form the ammeter
The current meter G of FIG. 3 has a rated current of 100uA and a full-scale adjustment potentiometer P2The output resistance of the operational amplifier is '0', the operational amplifier has constant voltage characteristic and can be equivalent to an ideal voltage source, and after the operational amplifier is loaded, the operational relationship of the circuit is unchanged, namely, the relationship between the internal resistance of the voltmeter meter head and the ideal voltage source is not large, so that the accurate voltage measurement can be completed by the ammeter with low accuracy.
This design is a relatively cost-effective option for practitioners with insufficient funds.
Debugging
Before the power is switched on, the 100uA ammeter G is mechanically zeroed to make the pointer just lower than the zero point of the dial, then the power is switched on and the input is short-circuited to adjust the potentiometer P1Until an accurate zero indication is obtained.
The full-scale adjustment of each measuring range is troublesome, needs to be carefully adjusted, and utilizes the potentiometer P2Calibrating a voltmeter to enable full-scale deflection of three ranges to be 1V, 10V and 100V respectively, observing a graph in detail in FIG. 3, wherein the maximum value of the three ranges is divided by a voltage divider and is based on the 1V range, namely, no matter whether the input is 1V or 100V, the operational amplifier A1The inputs of the inverting terminals are all 1V, the output of the operational amplifier is also 1V, and the potentiometer P is adjusted2The voltage of 1V makes the 100uA current meter fully biased.
Therefore, the calibration process of the voltmeter is simply described by taking the full-scale deflection calibration of the 1V range as an example.
The full-scale calibration of the ammeter (the meter head is connected with a slide wire resistor in parallel) requires preparing a standard ammeter to be connected in series with the ammeter to be calibrated, connecting the range current of the standard ammeter, adjusting the slide wire resistor to enable the ammeter to be calibrated to be full-scale, and completing the calibration.
The voltmeter calibration process is similar, and the voltmeter to be calibrated (actually, the ammeter G) is connected with the slide wire resistor W in series2The two units and a standard voltmeter Vr(1V full bias) parallel connection, and slide wire resistance W is adjusted1Outputting standard range voltage 1V, adjusting slide wire resistance W2The voltmeter (actually, the ammeter G) to be calibrated is full scale, and the debugging can be completed, as shown in fig. 4.
The accuracy of the high impedance analog dc voltmeter depends on the quality of the 100uA current meter G and the fineness of calibration, and if necessary, the divider resistance at the input end needs to be adjusted accordingly.
The power supply of the circuit can be selected from 8V-20V, and when a 12V power supply is adopted, the working current of the circuit is not more than 6 mA.
Matters of use
The use of a voltmeter should note the following:
1) the meaning of each symbol on the dial and the main function of each knob and selection switch are familiar.
2) Mechanical zeroing is performed.
3) According to the type and size of the measured object, the gear and the range of the change-over switch are selected, and the corresponding scale mark is found out.
4) And selecting the position of the meter pen jack.
5) Measuring voltage: when measuring voltage, a good measuring range is selected, and if a small measuring range is used for measuring a large voltage, the risk of meter burning exists; if a large amount of range is used to measure a small voltage, the pointer deflection is too small to read. The range is selected to try to deflect the pointer to around 2/3 full scale. If the magnitude of the measured voltage is not known in advance, the highest range is selected first, and then the range is gradually reduced to an appropriate range.
If the meter pen is reversely connected, the pointer at the head of the meter can deflect in the opposite direction, and the pointer is easy to bend.
The pointer type direct current voltmeter is designed based on an in-phase proportional operation circuit with infinite input impedance, and the output resistance of an amplifier is zero, so that the precision of the voltmeter can be basically guaranteed, the pointer type direct current voltmeter belongs to an ideal direct current voltmeter, and the pointer type direct current voltmeter is high in practical value and easy to popularize.
Claims (2)
1. A high impedance pointer type direct current voltmeter is characterized in that: the direct-current voltmeter comprises a resistance network voltage divider circuit, a range conversion switch circuit, an amplitude limiting circuit, a filter circuit, an in-phase proportion operation circuit, an input offset voltage adjusting circuit, a range full-scale deflection adjusting circuit, a galvanometer circuit and a direct-current power supply circuit, wherein resistors R1, R2, R3, R4 and R5 are sequentially connected in series to form the resistance network voltage divider circuit, the voltage divider circuit is bridged at two ends of voltage to be measured, a range selector S forms the range conversion switch circuit, a 1V gear movable contact of the range selector S is connected with the upper end of a resistor R1, a 10V gear movable contact of the range selector S is connected with connection points of a resistor R2 and a R3, and a 100V gear movable contact of the range selector S is connected with connection points of a resistor R4 and a resistor R5; the operational amplifier A1 and the resistor R7 form the in-phase proportional operation circuit, a static contact of the range selector S is connected with the in-phase input end of the operational amplifier A1 through an input resistor R6, the diode D1 forms the amplitude limiting circuit, the electrolytic capacitor C1 forms the filter circuit, the in-phase input end of the operational amplifier A1 is connected with a working ground through a reversely connected diode D1, and the in-phase input end of the operational amplifier A1 is connected with the working ground through a positively connected capacitor C1; the resistor R8 and the potentiometer P1 form the input offset voltage adjusting circuit, the potentiometer P1 is bridged between a pin 1 and a pin 5 of the operational amplifier A1, and the sliding end of the potentiometer P1 is connected with the working ground through the resistor R8; the potentiometer P2 forms the full-scale deflection regulating circuit, the galvanometer G forms the galvanometer circuit, the output end of the operational amplifier A1 is connected with a working ground through the resistor R9, the potentiometer P2 and the galvanometer G in sequence, and the negative end of the galvanometer G is connected with the working ground; the +/-12V power supply, the resistors R10 and R11 and the electrolytic capacitors C2 and C3 form the direct current power supply circuit.
2. The high impedance pointer type direct current voltmeter according to claim 1, wherein: in the in-phase proportional operation circuit, the output end of the operational amplifier A1 is connected with the inverting input end of the operational amplifier A1 through a resistor R7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120538362.1U CN214585670U (en) | 2021-03-16 | 2021-03-16 | High-impedance pointer type direct current voltmeter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120538362.1U CN214585670U (en) | 2021-03-16 | 2021-03-16 | High-impedance pointer type direct current voltmeter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN214585670U true CN214585670U (en) | 2021-11-02 |
Family
ID=78354230
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202120538362.1U Expired - Fee Related CN214585670U (en) | 2021-03-16 | 2021-03-16 | High-impedance pointer type direct current voltmeter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN214585670U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114167130A (en) * | 2021-12-17 | 2022-03-11 | 常州同惠电子股份有限公司 | Voltage detection circuit and method of precision voltmeter for measuring high internal resistance power supply |
-
2021
- 2021-03-16 CN CN202120538362.1U patent/CN214585670U/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114167130A (en) * | 2021-12-17 | 2022-03-11 | 常州同惠电子股份有限公司 | Voltage detection circuit and method of precision voltmeter for measuring high internal resistance power supply |
| CN114167130B (en) * | 2021-12-17 | 2024-04-02 | 常州同惠电子股份有限公司 | Voltage detection circuit and method for precise voltmeter for high-internal-resistance power supply measurement |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US9935598B2 (en) | Differential amplifier design as the preamp of DMM | |
| CN110161313B (en) | High-precision resistance measurement system and method combining differential method and proportional method | |
| CN110275104B (en) | Weak current measurement device and measurement method of ATE system | |
| WO2021184740A1 (en) | Current calibration device for power supply channel in test system, and correction method therefor | |
| CN1299119C (en) | Direct current resistance comparison measurement method and measuring instrument | |
| CN214585670U (en) | High-impedance pointer type direct current voltmeter | |
| CN204347229U (en) | The calibrating installation of active leakage current tester | |
| CN104535954B (en) | Calibration device and method of active leakage current tester | |
| CN102590632B (en) | Insulation resistance test circuit for circuit board | |
| CN211652972U (en) | Linear scale ohmmeter based on constant current source | |
| CN108572273B (en) | Low current measuring circuit and measuring method thereof | |
| CN214585719U (en) | Low impedance magnetoelectric DC microammeter | |
| CN204988943U (en) | High accuracy metal material fatigue damage test instrument | |
| US7429856B1 (en) | Voltage source measurement unit with minimized common mode errors | |
| CN210803660U (en) | Weak current measuring device of ATE system | |
| CN209496301U (en) | An output voltage adjustment device for a high-voltage power supply dedicated to a photomultiplier tube | |
| RU2397500C1 (en) | Resistance-to-voltage converter | |
| CN110954730A (en) | Linear scale ohmmeter based on constant current source and manufacturing method | |
| CN2697658Y (en) | High-precision interval type voltage meter | |
| CN220543028U (en) | Power supply internal resistance parameter measuring circuit and power supply internal resistance measuring instrument | |
| CN220064326U (en) | Variable gain instrument amplifier circuit of battery internal resistance tester | |
| CN219738060U (en) | uA level high-precision constant current source system | |
| CN117193456A (en) | Current source design circuit for measuring resistive load | |
| CN103760406B (en) | For the collection amplifying circuit of floating weak current | |
| CN109917840B (en) | Output voltage adjustment device for high-voltage power supply for photomultiplier tube |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20211102 |