JPH08166415A - Insulation resistance meter - Google Patents

Abstract

PURPOSE: To decide whether a discharge has completed or not by indicating the discharged amount on a meter when a resistor to be measured is discharged. CONSTITUTION: A switch 14 connects the input terminal 11a of a high voltage generating means 11 selectively with one measuring terminal 13a or a battery 10. Under a state where a resistor Rx to be measured is connected between measuring terminals 13a and 13b, the measuring terminal 13a is connected through the switch 14 with the input terminal 11a of the high voltage generating means 11 thus forming a discharge circuit from the measuring terminals 13a through a common wiring C of the high voltage generating means 11 and a meter M to the measuring terminals 13b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation resistance tester, and more particularly to an insulation resistance tester provided with a discharge circuit for discharging the electric charge accumulated in a resistance to be measured during measurement.

[0002]

2. Description of the Related Art As illustrated in FIG. 3, an insulation resistance tester includes a pair of measuring terminals 1 to which a resistor Rx to be measured is connected.
A predetermined high voltage is applied from a high voltage generating means 2 to a and 1b, and the current flowing through the resistor Rx to be measured is detected by the meter indicating circuit 3.

In this case, the high voltage generating means 2 includes a battery as a power source, a DC-AC converting circuit for boosting the output voltage of the battery and converting it into AC, and a rectifying / smoothing circuit for rectifying the AC output. And a high voltage of, for example, about 500 V is applied from the high voltage generating means 2 to the resistor Rx to be measured.

Therefore, when the resistor Rx to be measured has a capacitance component, the high voltage thereof charges the resistor Rx to be measured, and leaving it as it is may cause an accident such as electric shock. Therefore, it is necessary to discharge after the measurement.

Therefore, in the conventional case, the measuring terminal 1
A switch SW for opening and closing them and a discharge resistor Rd are inserted between a and 1b, the switch SW is turned off during the measurement, and the switch SW is turned on after the measurement, and the measured resistor Rx is charged. Electric charges are caused to flow through the discharge resistor Rd to be discharged.

[0006]

According to this, although it is possible to discharge the electric charge of the resistor to be measured, it is impossible to know whether or not the discharge is completed. Therefore, for example, when the ON time of the switch SW is not sufficient, the electric charge still remains in the resistor to be measured, which may cause an electric shock accident.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and the first purpose thereof is to recognize whether or not sufficient discharge is performed by shaking the meter even during discharge. It is to provide an insulation resistance tester capable of performing the above.

A second object of the present invention is to provide an insulation resistance tester capable of accurately measuring the exhausted state of a battery by utilizing the discharge circuit.

[0009]

In order to achieve the above first object, the present invention provides a battery as a power source and a DC-AC conversion circuit for boosting the output voltage of the battery and converting it into an AC voltage. And a high voltage generating means including a rectifying / smoothing circuit for rectifying the output of the DC / AC converting circuit, and a pair of measuring terminals connected to the resistor to be measured and to which a predetermined measuring voltage is applied from the high voltage generating means. , A measuring circuit connected to one of the measuring terminals and a common wiring of the high voltage generating means connected to one of the electrodes of the battery, for measuring the current flowing through the resistor to be measured, and the measurement by the measuring circuit. In an insulation resistance tester comprising a meter for displaying current, a first switch for selectively connecting the input terminal of the high voltage generating means to either the other measuring terminal or the other electrode of the battery. The other end by connecting the other measuring terminal to the input terminal of the high voltage generating means by the first switch in a state in which the resistance to be measured is connected between the measuring terminals. A discharge circuit is formed from the measurement terminal to the one measurement terminal via the common wiring of the high voltage generating means and the meter.

In this case, the other measuring terminal and the first measuring terminal
Preferably, a diode is connected between the switch and the discharge circuit so that the discharge current flows in the same direction as the current measured by the measurement circuit when the discharge circuit is formed.

The measuring circuit includes a pair of transistors formed by connecting the respective emitters of the first transistor to which the measuring current is supplied and the second transistor to which the reference current is input, and the emitter connection point. A logarithmic conversion circuit including a first operational amplifier that absorbs a current that appears and a second operational amplifier that absorbs a current that appears at the base of the second transistor is preferable. In that case, one end of the meter is connected to the common wiring, The other end of the meter is connected in parallel to the second operational amplifier and the one measuring terminal.

On the other hand, in order to achieve the above-mentioned second object, the present invention provides a predetermined battery between the output terminal of the high-voltage generating means connected to the other measuring terminal side and the first switch. And a second and a third switch which are connected to a resistance that causes a load state of the battery, and which are turned on and off in association with the other electrode of the battery and the one measuring terminal and the input terminal of the high voltage generating means. Connect each one, and the above first
By switching the switch to the other measurement terminal side and turning on the second and third switches, the high voltage generating means is brought into the operating state, and the resistance is used as an actual load to indicate the consumption state of the battery by the meter. The feature is that it is displayed.

[0013]

According to the above construction, since the meter is inserted in the discharge circuit of the resistor to be measured, it is possible to know from the display of the meter whether the discharge is completed.

Further, when the battery is checked, the resistance in the discharge circuit acts as an actual load, and therefore it is possible to accurately determine whether or not the consumption state of the battery is in a range that does not affect the resistance measurement. it can.

[0015]

Embodiments of the present invention will be described below. FIG. 1 schematically shows a block diagram of an insulation resistance meter according to this embodiment. According to this, the insulation resistance meter boosts an output voltage of the battery 10 and a battery 10 as a power source. Further, it is provided with a DC-AC conversion circuit 11 which is composed of, for example, a blocking oscillator for converting into an AC voltage, and a rectifying / smoothing circuit 12 which rectifies the AC output.

The DC-AC converting circuit 11 and the rectifying / smoothing circuit 12 constitute a high voltage generating means, and the high voltage generating means applies a predetermined measuring voltage to the pair of measuring terminals 13a and 13b. In this case, the DC-AC conversion circuit 1
The first input terminal 11a on the positive electrode side is provided with a first switch 14 for selectively connecting the input terminal 11a to either the positive electrode side of the battery 10 or one of the measurement terminals 13a.

That is, the first switch 14 is the battery 1
One of the outputs of the rectifying / smoothing circuit 12 that has an on-contact 14a connected to the positive electrode side of 0 and an off-contact 14b connected to one measurement terminal 13a, and is connected to the same off-contact 14b and the measurement terminal 13a. A series circuit of a diode D1 and a resistor Rd is inserted between the side and the side. The forward direction of the diode D1 is from the measurement terminal 13a to the off contact 14b.
Oriented to face side.

The other output terminal of the rectifying / smoothing circuit 12 is a common wiring C connected to the negative electrode side of the battery 10, and a resistor Rx to be measured flows between the common wiring C and the other measuring terminal 13b. A measuring circuit 15 for measuring a current and a meter M as an indicating instrument are connected in parallel.

A diode D2 is connected between the other measuring terminal 13b and the measuring circuit 15, and a diode D3 is connected between the other measuring terminal 13b and the meter M.
Is connected. In this case, the diode D2 is oriented such that its forward direction faces from the measuring terminal 13b to the measuring circuit 15 side, while the diode D3 is oriented such that its forward direction faces from the meter M to the measuring terminal 13b side. ing.

On the output side of the rectifying / smoothing circuit 12, a voltage detecting circuit 1 for detecting the voltage between the measuring terminals 13a and 13b.
6 is provided. This voltage detection circuit 16 is, for example, 2
It consists of a voltage divider circuit with two resistors connected in series, and the reference voltage is taken out from the connection point. This reference voltage is input to the control circuit 17, and the control circuit 17 controls the DC-AC conversion circuit 11 based on the reference voltage so that the output voltage of the rectifying / smoothing circuit 12 becomes constant.

In this embodiment, the measurement circuit 15 is a logarithmic conversion circuit. As shown in FIG. 2, the logarithmic conversion circuit 15 is composed of two NPN transistors Q1 and Q2 having the same characteristics, two operational amplifiers (operational amplifiers) IC1 and IC2, and five resistors R1 to R5. ing.

That is, the emitters of the transistors Q1 and Q2 are connected to each other, and one of the transistors Q1 is connected.
Is supplied with a measurement current Ix flowing through the resistor Rx to be measured via the resistor R1, and the measurement current Ix is supplied to the transistor Q.
1 through the collector → emitter → resistor R5 to the output point of the operational amplifier IC2.

When the reference voltage output from the voltage detection circuit 16 is V, the other transistor Q2 has a voltage V / R.
A current Iref determined by 2 flows into the output point of the operational amplifier IC2 through its collector → emitter → resistor R5.

The operational amplifier IC is connected to the base of the transistor Q2 via a series circuit of a diode D4 and a resistor R4.
One output point is connected. In addition, this operational amplifier IC1
The negative side input terminal of is connected to the connection point of the resistor R1 and the transistor Q1, and the positive side input terminal of the operational amplifier IC1 is the common wiring C of common potential with the base of the transistor Q1.
It is connected to the. The negative input terminal of the operational amplifier IC2 is connected to the connection point between the resistor R2 and the transistor Q2, and the positive input terminal thereof is connected to the common wiring C.

For this logarithmic conversion circuit 15, a meter M
Has one end connected to the common line C and the other end connected to the connection point between the base of the transistor Q2 and the resistor R4 via the resistor R3. Further, as described above, the other end of the meter M is connected to the measurement terminal 13b via the diode D3.

Here, the base-emitter voltages Vbe1 and Vbe2 of the transistors Q1 and Q2 depend on the currents Ix and Iref, respectively, but since the base of the transistor Q1 has a common potential, the emitter voltage of the transistor Q1. Becomes -Vbe1 and the base voltage Va of the transistor Q2 becomes -Vbe1 + Vbe2.

That is, the base voltage Va of the transistor Q2 becomes the difference ΔVbe between the base and emitter voltages of the two transistors Q1 and Q2, and the current Ix is given by the following equation.
And Iref are proportional to the natural logarithm of the ratio. Note that k in the equation
Is the Boltzmann coefficient, q is the electron charge (coulomb), and T is the absolute temperature (K).

Va = ΔVbe = −kT / q · log (Ix / Iref) ... Since the base voltage Va of the transistor Q2 is proportional to the logarithm of the current Ix flowing through the resistor Rx to be measured,
A current Im represented by the following equation flows through the meter M, and the resistance value of the resistor Rx to be measured is displayed on the meter M. In the equation, A is kT / q, Rm is the resistance of the meter M, and these constants A, Iref, R3 and Rm are used.
Is known.

Im = −A · log (Ix / Iref) · {1 / (R3 + Rm)} ... In addition, the insulation resistance tester separates the positive electrode of the battery 10 from the DC-AC conversion circuit 11 separately from the first switch 14. Input terminal 1
2nd switch 18 for connecting to 1a, input terminal 11a of DC-AC conversion circuit 11, and measurement terminal 13b
And a third switch 19 which is provided between the second switch 18 and the second switch 18 and is turned on and off in cooperation with the second switch 18. In this embodiment, the second switch 18 is a transistor switch and is normally off, but the third switch 19
It is set to turn on at the same time by turning on.

Next, the operation of the present invention will be described. First, at the time of resistance measurement, the measured resistor Rx is connected to the measurement terminal 13
Inserted between a and 13b, the first switch 14 is switched to its ON contact 14a side. As a result, the voltage of the battery 10 is boosted to a predetermined voltage by the DC-AC conversion circuit 11 and converted into an AC voltage, which is then converted to a DC high voltage by the rectifying / smoothing circuit 12 and applied to the resistor Rx to be measured.

Along with this, the current Ix flowing through the resistor Rx to be measured flows into the transistor Q1 side of the logarithmic conversion circuit 15 via the diode D2 and the resistor R1. At this time, the reference current I based on the reference voltage V detected by the voltage detection circuit 16 is applied to the transistor Q2 of the logarithmic conversion circuit 15.
Since ref is supplied via the resistor R2, the current Im according to the above equation flows through the meter M, and the resistance value of the resistor Rx to be measured is displayed on the meter M.

After the measurement, if the resistance Rx to be measured has a capacitance component, the first switch 14 is turned off.
Switch to side b. As a result, the electric charge charged on the resistor Rx to be measured passes through one measurement terminal 13a → resistance Rd → diode D1 → common wiring C → meter M → diode D3 of the high voltage generating means including the DC-AC conversion circuit 11. It is discharged along the path to the other measurement terminal 13b.

As described above, according to the present invention, the meter M is inserted in the discharge path, and the direction of the discharge current flowing through the meter M by the diode D1 is the same as the current Im flowing during resistance measurement. Therefore, the discharge current amount is displayed on the meter M, and it is possible to know whether or not the discharge is completed by the meter display.

To measure the consumption state of the battery 10, the measurement terminals 13a and 13b are opened and the first switch 1
The second and third switches 18 and 19 are both closed while the switch 4 is on the side of the off contact 14b. As a result, a high voltage is generated via the DC-AC conversion circuit 11 and the rectifying / smoothing circuit 12 as in the resistance measurement, and the high voltage is generated by the resistance R.
applied to d. Since the current consumption of the battery 10 greatly changes depending on the resistance value of the resistor Rx to be measured, the resistance Rd
Is set to the resistance value when the current consumption becomes maximum.

Therefore, the battery 10 is in the state of maximum current consumption, and the current obtained by (battery voltage E / resistor R1) is applied to the transistor Q1 of the logarithmic conversion circuit 15, and the meter is measured in the same manner as the above resistance measurement. In M, the battery voltage when the current consumption is maximum is displayed.

The current Im flowing in the meter M at the time of resistance measurement is obtained from the above equation, but normally Ix> Ir
Since it is ef, the current Im is also negative, the base voltage Va of the transistor Q2 and the output point voltage Vb of the operational amplifier IC1.
Is also negative, and the meter M is connected so that the pointer properly swings according to the negative current Im.

However, when the measurement terminals 13a and 13b are open, Ix <Iref except when the consumption state of the battery 10 is measured. Therefore, the current Im and the voltages Va and Vb are Since both have positive polarity, the pointer of the meter M swings in the direction outside the operating range.

In order to prevent this, in this embodiment, the diode D4 is inserted so that the positive current Im does not flow to the output point of the operational amplifier IC1 when the measurement terminals 13a and 13b are opened.

[0039]

As described above, according to the present invention,
The following effects are obtained. That is, according to the first aspect of the invention, since the meter is inserted in the discharge circuit that discharges the electric charge charged in the resistor to be measured, it is possible to know whether the discharge is completed by the display of the meter. it can.

According to the invention of claim 2, a diode for connecting the discharge current to the meter in the same direction as the current measured by the measuring circuit is connected in the discharge circuit. Therefore, the meter display can be read with the same feeling as when measuring resistance.

Further, according to the third aspect, since the measuring circuit is composed of the logarithmic conversion circuit, the discharge current at the time of discharging does not flow into the same logarithmic conversion circuit and passes through only the meter.

On the other hand, according to the invention of claim 4, a resistor having a resistance value that maximizes the current consumption of the battery is provided in the discharge circuit. It is possible to accurately determine whether or not the consumption state of the battery as a load is in a range that does not affect the resistance measurement.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of an insulation resistance meter according to the present invention.

FIG. 2 is a circuit diagram of a logarithmic conversion circuit applied to the same embodiment.

FIG. 3 is a schematic block diagram for explaining a conventional insulation resistance meter.

[Explanation of symbols]

 10 Battery 11 DC-AC conversion circuit 12 Rectifying / smoothing circuit 13a, 13b Measurement terminal 14 First switch 15 Measurement circuit (logarithmic conversion circuit) 16 Voltage detection circuit 17 Control circuit 18 Second switch 19 Third switch Q1, Q2 Transistor IC1, IC2 operational amplifier Rd, R1 to R5 resistance D1 to D4 diode

Claims (4)

[Claims] 1. A high-voltage battery including a battery as a power source, a DC-AC conversion circuit for boosting an output voltage of the battery and converting the output voltage to an AC voltage, and a rectifying / smoothing circuit for rectifying an output of the DC-AC conversion circuit. A pair of measuring terminals connected to the voltage generating means and the resistance to be measured, to which a predetermined measuring voltage is applied from the high voltage generating means, and the high voltage connected to one of the measuring terminals and one electrode of the battery. In the insulation resistance tester, each of which is connected to the common wiring of the generating means and includes a measurement circuit for measuring a current flowing through the resistance to be measured and a meter for displaying a measurement current by the measurement circuit, A first switch for selectively connecting the input terminal of the voltage generating means to either the other measurement terminal or the other electrode of the battery, wherein the measured resistor is connected between the measurement terminals. In this state, by connecting the other measuring terminal to the input terminal of the high voltage generating means by the first switch, the other measuring terminal is connected through the common wiring of the high voltage generating means and the meter. An insulation resistance meter characterized in that a discharge circuit reaching one of the measurement terminals is formed. 2. When the discharge circuit is formed between the other measurement terminal and the first switch, the discharge current flows through the meter in the same direction as the measurement current by the measurement circuit. The insulation resistance meter according to claim 1, further comprising a diode connected thereto. 3. The measurement circuit includes a first transistor to which the measurement current is supplied and a second transistor to which a reference current is input.
Logarithmic conversion including a pair of transistors in which the respective emitters of the transistors are connected to each other, a first operational amplifier that absorbs a current that appears at the emitter connection point, and a second operational amplifier that absorbs a current that appears in the base of the second transistor 2. A circuit, wherein one end of the meter is connected to the common wiring, and the other end of the meter is connected in parallel to the second operational amplifier and the one measuring terminal, respectively. Insulation resistance meter described in. 4. A resistor for generating a predetermined load state in the battery is connected between the output terminal of the high voltage generating means connected to the other measurement terminal side and the first switch, and the battery is connected to the resistor. A second electrode and a third switch, which are turned on and off in conjunction with each other, are connected between the other electrode and the one measuring terminal of the high voltage generating means, and the input terminal of the high voltage generating means. By switching to the other measurement terminal side and turning on the second and third switches, the high voltage generating means is brought into an operating state, and the consumption state of the battery is displayed on the meter by using the resistance as an actual load. The insulation resistance tester according to claim 1, wherein the insulation resistance tester is configured to operate.