JP3716308B2 - High resistance measuring method and high resistance measuring apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high resistance measurement method and a high resistance measurement device, and more particularly, resistance of a resistor having an extremely high resistance value of about 10 ¹⁰ to 10 ¹⁴ Ω, such as a terminal-case insulation resistance of a Zener standard voltage generator. The present invention relates to a value measuring method and a measuring apparatus.
[0002]
[Prior art]
At present, a Zener standard voltage generator whose voltage value is accurately known as shown in FIG. 5 is used for calibration of a measuring instrument or a voltmeter performed by a manufacturer or the like. In FIG. 5, E1 and E2 are voltage sources, R1 to R9 are resistors, ZD is a Zener diode, 1 is a voltage control circuit, 2 is an amplifier, and 3 is a case of a Zener standard voltage generator. In this standard voltage generator, the circuit is operated so as to eliminate the voltage difference between the two input terminals of the amplifier 2 to generate a constant voltage. For example, 10 V from the terminal H is applied to the terminal T1 using the terminal L as a reference potential terminal. For example, 1.018V is obtained from the terminal T2, and for example 1.0V is obtained from the terminal T2. The user of the Zener standard voltage generator performs calibration by connecting two terminals of an electronic device to be calibrated, for example, a voltmeter to a terminal L of the Zener standard voltage generator and, for example, a terminal H. At this time, the voltage value of the Zener standard voltage generator changes depending on the magnitude of the insulation resistance Rx. Therefore, unless the value of the insulation resistance is accurately measured and the magnitude of the error is not clarified, the calibration of the measuring instrument or the voltmeter becomes inaccurate. Thus, it is generally not easy to measure the insulation resistance. This is because the insulation resistance is extremely high, and the influence of leakage current that exists everywhere in the circuit must be removed.
[0003]
As a technique for measuring this type of resistance value, a minute current measurement method has been generally used. As shown in FIG. 6, this method is a method in which a minute current I flowing through a known voltage value E and an insulation resistance Rx is obtained by an ammeter A and calculated as Rx = E / I. At this time, as shown in FIG. 6, Irg and Ieg called leakage currents flow through the surface and the inside of the insulator. Since Irg flows to the ammeter as an extra current, it affects the measured value of the current I flowing through the insulation resistance Rx, and Ieg takes the extra current from the power supply and lowers the voltage value E. . In order to prevent this, it is common practice to use a power supply with a small internal resistance and to provide a shielding plate 4 called a shield as shown in FIG. Normally, the shielding plate 4 allows the leakage current Irg to flow through the outer shield and does not pass through the ammeter so that accurate measurement can be performed.
Further, as a resistance measuring method, there is a method of measuring a resistance value by assembling a Wheatstone bridge with one side of the resistor to be measured and obtaining an equilibrium condition of the bridge.
[0004]
[Problems to be solved by the invention]
When the conventional measurement method shown in FIG. 6 is used to measure the insulation resistance Rx between the measurement terminal of the Zener standard voltage generator and the case as shown in FIG. 5, the outer case portion is shown in FIG. Is connected to the measurement terminal of the ammeter, so that a leakage current Irg flows from the positive voltage portion of the electric circuit to the case. This leakage current naturally flows through the ammeter as an extra current, which affects the measured value. For this purpose, shielding is effective, but in order to shield the Zener standard voltage generator, as shown in FIG. 9, the entire case and measurement terminals are covered with an insulating material 5, and then the shielding plate 4 is covered. It must be provided and it becomes a very complicated shield.
In addition, in the method of obtaining the resistance value according to the Wheatstone bridge equilibrium condition, in order to measure a high resistance such as an insulation resistance, a high resistance resistor equivalent to the insulation resistance must be connected to a side other than the resistance to be measured. However, it is generally difficult to accurately determine the resistance value of such a high resistance resistor. It is also not easy to obtain a stable high resistance resistor.
An object of the present invention is to solve the above-described problems of the prior art, and the object of the present invention is to firstly configure a bridge for high resistance measurement without using high resistance. Secondly, the influence of the leakage current is eliminated without using a complicated shield, and the resistance value of the high resistance resistor can be measured with high accuracy.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, one end of the three resistors is connected to each of the first, second, and third points, and the other ends of the three resistors are commonly connected. The first resistor Y circuit is constituted by the three resistors, the resistor of the proportional side between the second point and the third point, the resistance to be measured between the fourth point and the first point, and the fourth point to the second point. Connect the reference resistor between the three points, connect the power supply between the first point and the third point , balance the circuit so that the fourth point becomes the ground potential, and then balance the second point and the fourth point Thus , there is provided a high resistance measuring method characterized in that a resistance value of a resistance to be measured is obtained.
Preferably, the resistor connected to the first point among the resistors constituting the resistor Y circuit is configured by the first variable resistor circuit.
[0006]
In order to achieve the above object, according to the present invention, one end of the three resistors is connected to each of the first, second, and third points, and the other ends of the three resistors are commonly connected. The first resistor Y circuit is constituted by the three resistors, the resistor on the proportional side between the second point and the third point , the resistance to be measured between the fourth point and the first point, and the fourth point. -Connect the reference resistor between the third point, the power source between the first point-the third point, and connect one end of the balanced detector to the fourth point, and connect the other end of the balanced detector to the second point and the ground point The resistance value of the resistance to be measured is obtained by balancing the second point and the fourth point after balancing the circuit so that the fourth point becomes the ground potential. A high resistance measuring device is provided.
Preferably, one end of a three resistor is connected to each of the ground point, the first point, and the third point, and the second resistor Y circuit is configured by the three resistors.
[0007]
[Action]
In the present invention, resistance measurement is performed using a Y-Δ conversion type bridge circuit. Even in a resistance Y circuit using a relatively low resistance resistor, a high resistance can be obtained equivalently by Y-Δ conversion, so a high resistance measurement bridge is configured using a low resistance resistor. It becomes possible. Furthermore, the leakage current existing in the bridge circuit is removed by equivalently grounding one point of the bridge circuit using a Y-Δ conversion type grounding device. According to this method, since the outer case is equivalently grounded, the outer case can be used as a shielding plate without covering the case and the measurement terminal with an insulating material. By this method, the leakage current can be compensated by the low resistance circuit of the Y-Δ conversion type grounding device.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a circuit diagram showing an embodiment of the present invention. In FIG. 1, the upper half circuit is a main circuit for measuring a resistance value, and the lower half circuit is a circuit constituting a grounding device. In FIG. 1, Rao, Rbo and Rco are Y resistors connected between points a, b and c with O point as the center, and Rx is connected between points a and d The insulation resistance of the Zener standard voltage generator, which is the resistor to be measured, Rs and rs are connected between the point c and the point d, the reference resistor having a known value, and the points R1 and r1 are the points b A proportional-side resistor connected between points c, D is a detector for balanced detection, one end of which is connected to point d, and the other end is switched to point b and ground via switch SW. And connected.
Rw2 and rw2, Rw3 and Rw4 are Y-connected between points a, c and e to form a second Y circuit, and Rw1 and rw1 are connected between points c and e. A proportional-side resistor, E, is a voltage source. Point e is grounded. Rw1, rw1, Rw2, rw2, Rw3, and Rw4 constitute a Y-Δ conversion type grounding device for removing the influence of leakage current.
[0009]
Of the above resistors, resistors Rao, rs, Rw4 and rw2 are variable resistors, Rao and rs are compensation circuits used to balance the bridge of the main circuit, and Rw4 and rw2 are balanced with leakage resistance. The compensation circuit for taking this is configured. 2A and 2B show variable ranges of the resistor Rao and the resistor rs. The compensation resistor Rao of the compensation circuit 1 is composed of four variable resistors, and the variable range of each range is 1 kΩ to 10 kΩ, then 10 kΩ to 100 kΩ, 100 kΩ to 1 MΩ, and finally 1 MΩ to 10 MΩ. That is, an arbitrary value from 1 kΩ to 10 MΩ can be set. The resistor rs of the compensation circuit 2 includes three variable resistors, and the variable range of each range is 100Ω to 1kΩ, then 1kΩ to 10kΩ, and finally 10kΩ to 100kΩ. However, Rs is 100 kΩ.
In the variable resistors Rw4 and rw2 of the grounding device, Rw4 corresponds to Rao and rw2 corresponds to rs. The variable ranges are as shown in FIGS. 2 (a) and 2 (b).
[0010]
A Y-type circuit constituted by Rao, Rbo and Rco equivalently forms a Δ-type circuit of resistors R2, Rac and Rcb. Here, Rao, Rbo >> Rco are set. Under this condition, in particular, the resistor R2 which is one side of the proportional side of the bridge is equivalently a very high resistor. Resistor R1 also becomes one side of the proportional side in the same way, but if resistor Rcb due to Y-Δ conversion is added in parallel, the parallel resistance value will deviate from the nominal value of R1, so resistor R1 for adjustment is connected in series. is there.
[0011]
The equivalent resistance value R2 is expressed by the following equation by Y-Δ conversion.
R2 ＝ Rao + Rbo + Rao ・ Rbo / Rco [Ω] (1)
It becomes. Here, Rao / Rbo / Rco >> Rao, Rbo,
R2 ≒ Rao ・ Rbo / Rco [Ω] (1 ')
From equation (1 ′), R2 is equivalently high resistance. Using this R2, the insulation resistance Rx is
Rx = (Rs + rs) ・ R2 / Rp [Ω] (2)
It becomes. However, Rp is Rp = (R1 + r1) · Rcb / (R1 + r1 + Rcb). From equation (2), the magnitude of the equivalent resistance R2 is determined by the value of the insulation resistance Rx. That is, the set value of the compensation resistor Rao in the equation (1 ′) is determined. At this time, for example, if the maximum value of 10 MΩ in the variable range is set as the set value, the remaining three variable resistors can set the remaining 3 digits from the top, but if the minimum value is 1 kΩ, the value is 1 from the top. It becomes only digits. In order to solve such a problem, the compensation circuit 2 is separately used. That is, the most significant digit is obtained only by the compensation resistor Rao, and the compensation resistor rs is used from the next digit. It is clear that this method is theoretically possible from the equations (1 ') and (2). By using this compensation method, it is possible to obtain an arbitrary insulation resistance value up to 1/1000 order. However, the measurement accuracy is estimated to be about 1%.
Similarly, the variable resistor Rw4 is used to set the first digit, and the variable resistor rw2 is used to set the remaining three digits from the top.
[0012]
The measurement procedure is described below. First, the switch SW is set to the ground side, and the detector D is grounded. The bridge configuration at this time is as shown in FIG. The leakage resistances Rh1 and Rh2 that cause the leakage current are all concentrated and distributed at the point e, which is the ground potential on the grounding device side, and are configured as if they are part of the grounding device. The In this state, the compensation resistors Rw4 and rw2 are adjusted so that the bridge circuit is balanced. At the time of equilibrium, both ends e and d of the detector D have the same potential. Next, when the switch SW is switched and the detector D is set to the point b side, the bridge configuration is as shown in FIG. Using this main circuit, the insulation resistance of the Zener standard voltage generator is measured. Although the point d is apparently floating from the ground, since the ground potential is equivalently held by the previous equilibrium operation, the case of the Zener standard voltage generator is forced to the ground potential, It will serve as a shielding plate. The balance of the main circuit is obtained by adjusting the compensation resistors Rao and rs and is detected by the detector D. The equilibrium condition formula at this time becomes the following formula from the formulas (1 ′) and (2).
Rx = (Rs + rs) ・ RaoRbo / RcoRp [Ω] (3)
Here, Rbo = 100kΩ, if it is assumed that the selection and Rp = 1 k [Omega and Rco = 1 [Omega, the ^{Rbo / Rp · Rco = 10 2} . From this, equation (3) becomes
Rx = (Rs + rs) Rao × 10 ² [Ω] (4)
Given in. Therefore, the insulation resistance Rx of the Zener standard voltage generator is obtained.
[0013]
By adjusting rs, the balance between the main circuit and the grounding device is lost. Therefore, if rs is larger than Rs and the variable amount of rs is large during adjustment of the main circuit, it is necessary to obtain the equilibrium condition of the main circuit again after adjusting point d to the ground potential again. When rs is smaller than Rs or when the amount of change in rs is small, sufficiently high-precision measurement can be performed without readjustment.
[0014]
Although the preferred embodiments have been described above, the present invention is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the scope of the present invention. For example, the resistors Rao and rs are not necessarily constituted by four to three variable resistors, but may be other numbers, and the variable range thereof does not have to be as in the embodiment. Further, the variable range of the resistors Rw4 and rw2 need not be the same as that of the resistors Rao and rs. Further, the present invention is advantageously used for measuring the insulation resistance of a Zener standard voltage generator, but is not limited to this application, and can be applied to the measurement of insulation resistance of other standard devices and measuring instruments and other high resistances. .
[0015]
【The invention's effect】
As described above, the present invention measures a high resistance value such as an insulation resistance by using a Y-Δ conversion type main circuit bridge. A high resistance of about ¹⁰ to 10 ¹⁴ Ω can be measured with high accuracy of the upper three digits. Also, by using a Y-Δ conversion type grounding device, one point of the main circuit bridge is equivalently grounded, so that the effect of leakage current on the main circuit floating from the ground in terms of circuit is compensated for by a low resistance. It can be removed with a grounding device having
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of the present invention.
FIG. 2 is a diagram for explaining a configuration of a resistor Rao and a resistor rs.
FIG. 3 is a diagram for explaining the operation of an embodiment of the present invention (No. 1).
FIG. 4 is a diagram for explaining the operation of the embodiment of the present invention (No. 2).
FIG. 5 is a diagram showing a schematic configuration of a Zener standard voltage generator.
FIG. 6 is a diagram showing a conventional resistance measuring method (No. 1).
FIG. 7 is a diagram showing a conventional resistance measuring method (No. 2).
FIG. 8 is a diagram (part 1) for explaining problems of the conventional example.
FIG. 9 is a diagram (part 2) for describing problems of the conventional example.
[Explanation of symbols]
1 Voltage Control Circuit 2 Amplifier 3 Case 4 Shielding Plate 5 Insulating Material

Claims (21)

The first resistor Y circuit is configured by the three resistors such that one end of the three resistors is connected to each of the first, second, and third points and the other ends of the three resistors are commonly connected. , A proportional side resistor between the second point and the third point, a resistance to be measured between the fourth point and the first point, a reference resistance between the fourth point and the third point, and a first point to the third point connect the power between the points, after the fourth point to balance the circuit so that the ground potential, wherein the determination of the resistance value of the measured resistance by Rukoto equilibrated second point and a fourth point High resistance measurement method. 2. The high resistance measuring method according to claim 1, wherein a resistor connected to the first point among the resistors constituting the first resistor Y circuit is constituted by a first variable resistor circuit. . The high resistance measuring method according to claim 2, wherein the variable range of the first variable resistance circuit is four digits. 4. The high resistance measuring method according to claim 1, wherein a resistance value of the reference resistor is variable. The resistance value of the reference resistor is variable in a range of R to 2.111R (where R is an arbitrary resistance value of 10 kΩ to 1 MΩ), and its minimum variable width is R / 1000. Item 5. The high resistance measurement method according to Item 4. 6. The high resistance measuring method according to claim 1, wherein the first auxiliary resistor is connected between the second point and the third point. 7. The high resistance measurement method according to claim 1, wherein the measurement is performed by adjusting the potential of the fourth point to the ground potential without grounding the fourth point. The first resistor Y circuit is configured by the three resistors such that one end of the three resistors is connected to each of the first, second, and third points and the other ends of the three resistors are commonly connected. , A proportional side resistor between the second point and the third point, a resistance to be measured between the fourth point and the first point, a reference resistance between the fourth point and the third point, and a first point to the third point power between the points, to connect one end of the balanced detector to the fourth point, the other end of the balance detector configured to be switched connected to the ground point and the second point, and the fourth point ground potential A high resistance measuring apparatus characterized by obtaining a resistance value of a resistance to be measured by balancing a second point and a fourth point after the circuit is balanced in such a manner . 9. The high resistance measuring device according to claim 8, wherein a resistor connected to the first point among the resistors constituting the first resistor Y circuit is constituted by a first variable resistor circuit. . The high resistance measuring device according to claim 9, wherein the first variable resistance circuit includes a plurality of variable resistors having different variable ranges. 11. The reference resistor is constituted by a reference fixed resistor and a second variable resistor circuit, and a variable range of the second variable resistor circuit is about the resistance value of the reference fixed resistor. The high resistance measuring device according to any one of the above. The high resistance measuring apparatus according to claim 11, wherein the second variable resistance circuit includes a plurality of variable resistors having different variable ranges. The high resistance measuring device according to claim 8, wherein a first auxiliary resistor is connected between the second point and the third point. The high resistance measuring apparatus according to claim 13, wherein the first auxiliary resistor includes two fixed resistors. 15. The second resistor Y circuit is constituted by the three resistors so that one end of each of the three resistors is connected to the ground point, the first point, and the third point, respectively. The high resistance measuring device according to any one of the above. 16. The high resistance measuring device according to claim 15, wherein a resistor connected to the first point of the resistors constituting the second resistor Y circuit is constituted by a third variable resistor circuit. . The high resistance measuring device according to claim 16, wherein the third variable resistance circuit includes a plurality of variable resistors having different variable ranges. Among the resistors constituting the second resistor Y circuit, the resistor connected to the ground point is constituted by a ground circuit fixed resistor and a fourth variable resistor circuit, and the variable range of the fourth variable resistor circuit is The high resistance measuring device according to claim 15, wherein the high resistance measuring device is about a resistance value of the ground circuit fixed resistor. 19. The high resistance measuring device according to claim 18, wherein the fourth variable resistance circuit includes a plurality of variable resistors having different variable ranges. The high resistance measuring device according to claim 15, wherein a second auxiliary resistor is connected between the ground point and the third point. 21. The high resistance measuring device according to claim 20, wherein the second auxiliary resistor is constituted by two fixed resistors.

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