JPH0539496Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a leakage current measuring device, and in particular a leakage current measuring device that measures leakage current by applying a predetermined voltage to an object to be measured consisting of an electric circuit or an electric element. Regarding.

(Prior Art) A conventional leakage current measuring device has a configuration shown, for example, in the block diagram of FIG. 2a. This leakage current measuring device includes a step voltage power supply 23 that applies a voltage E _C to an object to be measured 21, an ammeter 22, and a controller 25 that changes the output voltage E of the step voltage power supply 23 stepwise over time. It consisted of Figure 3 shows the step voltage power supply 2 in Figure 2.
FIG. 3 is a waveform diagram showing one cycle of the stepped voltage outputted by No. 3. This step voltage changes at the timing instructed by the controller 25 with the voltage control signal 125, and also rises by the step voltage V _S instructed by the voltage control signal 125 at that timing.

Figure 2b shows a manual power supply 26 for the circuit shown in figure a.
12 is a block diagram showing another conventional leakage current measuring device in which a switching relay 27 is added and the switching relay 27 enables selection of the applied voltage. FIG. The manual power supply 26 is used for the purpose of setting measurement conditions different from those of the step voltage power supply 23 and observing the leak state of the object to be measured 21. In the configurations shown in FIGS. 2a and 2b, different drop voltages _EV are generated depending on the current I flowing through the ammeter 22, so it is difficult to accurately apply a predetermined voltage to the object to be measured 21. FIG. 4a is a block diagram of a conventional example in which a function is added to correct the drop voltage _EV , which is a drawback of the configuration shown in FIG. Consists of.

4b shows a configuration similar to the configuration shown in FIG. 2b, with the addition of the function of switching the manual power supply 46 and selecting it with a relay 47 and measuring it with the same ammeter 42, but in reality, the function of switching the manual power supply 46 and selecting it with the same ammeter 42 is added. - A circuit for switching the feed back loop is required to prevent the loop from becoming open.

(Problems to be solved by the invention) In the conventional leakage current measuring device described above, in the configurations shown in FIGS. 2a and 2b, the drop voltage E _V of the ammeter 22 changes depending on the leakage current I, It is difficult to maintain the voltage E _C applied to the object 21 at a predetermined voltage. In addition, in the conventional example shown in FIGS. 4a and 4b, which compensates for this drawback, an ammeter 42 is included in the feed back loop of an operational amplifier 45, and supplies measurement output to the object under test from a separate power source such as a manual power source 46. The disadvantage was that it was necessary to switch the feed back loop when necessary.

(Means for Solving the Problems) Means for providing the present invention in order to solve the above-mentioned problems is to apply a voltage between the first and second terminals of an object to be measured consisting of an electric circuit or an electric element. a step voltage power supply that outputs a voltage that changes stepwise with respect to a reference potential according to instructions indicated by a voltage control signal, the leakage current measurement device measuring the leakage current of the measured object by applying voltage; A manually set voltage power source comprising a manual voltage setting means and outputting a voltage with a magnitude set in the manual voltage setting means and relative to the reference potential, and connected between the second terminal and the reference potential. an ammeter, a voltage follower that receives the voltage at the second terminal, a voltage adder that adds the output voltage of the voltage follower and the output voltage of the step voltage power supply, and an output voltage of the voltage adder. a current booster for amplifying current; and voltage selection means for selecting either the output voltage of the current booster or the output voltage of the manually set voltage power supply according to a voltage selection signal and guiding the selected one to the first terminal. , and a controller that outputs the voltage control signal and the voltage selection signal.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

The step voltage power supply 13 is a power supply that changes the voltage in fixed steps according to an external signal, and the ammeter 12
is connected between the object to be measured 11 and ground, the voltage follower 18 outputs the drop voltage E _V generated in the ammeter 12 as an input drop voltage signal, and the arithmetic unit 19 inputs the drop voltage E V generated in the ammeter 12 and outputs it as a drop voltage signal. The booster 20 receives the voltage output from the arithmetic unit 19 and amplifies the current, and the switching relay 17 receives the voltage output from the arithmetic unit 19 and amplifies the current.
The controller 15 outputs a voltage control signal 115a to the step voltage power supply 13 and a voltage selection signal 115b to the switching relay 17. The step voltage power supply 13 is connected to the controller 15
The output voltage E (hereinafter referred to as reference voltage E) is generated stepwise in a voltage value according to a predetermined sequence in accordance with the voltage control signal 115a sent from the output voltage control signal 115a, for example, in accordance with the waveform diagram shown in FIG. The ammeter 12 has a negative terminal connected to the ground and a positive terminal connected to the output of the device under test 11, and the leakage current I flowing through the device 11 multiplied by the internal resistance R is the drop voltage E _V (=RI).
It is. This drop voltage _EV is received by a voltage follower 18 having a high input impedance and sent as a drop voltage signal 118 to an arithmetic unit 19, where it is added to the reference voltage E mentioned above. The added voltage E+ _EV is given a current capacity as a measurement output by the booster 20, and is output to the object to be measured 11 through the switching relay 17. Since the voltage of the positive terminal of the object to be measured 11 is E+E _V with respect to the ground,
The applied voltage E _C of the object to be measured 11, which is obtained by subtracting the drop voltage E _V of the ammeter 12 (the potential of the negative terminal of the object to be measured 11 with respect to the ground) from this E+E _V , matches the reference voltage E. The controller 15 connects the switching relay 17 to the booster 20 side when controlling the step voltage power source 13 in an automatically determined sequence, and connects it to the manual power source 16 side when the sequence is completed. In this example,
By setting the voltage conditions different from the voltage conditions output by the step voltage power supply 13 using the manual power supply 16, the leak state of the DUT 11 can be checked while measuring the leakage current without changing the connection between the DUT 11 and the ammeter 12. can be observed.

(Effects of the invention) As explained above, the leakage current measuring device of the invention adds the drop voltage E _V generated in the ammeter 12 to the reference voltage E and outputs the resultant voltage E V to be applied to the object to be measured 11. _C can be made to match the reference voltage E. Therefore, the adoption of the present invention has the effect of improving measurement accuracy. moreover,
In the present invention, since the ammeter 12 is not included in the feed back loop of the voltage adder (consisting of an operational amplifier), different currents can be measured without changing the connection between the device under test 11 and the ammeter 12. (In the embodiment, the manual power source 16) can be switched to perform measurement. The present invention has such effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.
2a and 2b and 4a and 4b are block diagrams showing conventional examples, and FIG. 3 is a waveform diagram showing an example of the output voltage of a step voltage power supply. 11, 21, 41...Object to be measured, 12, 22,
42... Ammeter, 13, 23, 43... Step voltage power supply, 15, 25, 45... Controller,
16,26,46...Manual power supply, 17,2
7, 47... Switching relay, 18... Voltage follower, 19... Arithmetic unit (adder), 20
...Booster, 48...Operation amplifier, E...Reference voltage (output voltage of step voltage power supply 13), _EV ...
...Drop voltage of ammeter, E _C ...Voltage applied to the object to be measured, I ... Leak current, T _I ... Interval time, T _C ... Voltage application time, T _M ... Measurement time, V _S ... ...step voltage.

Claims (1)

[Scope of utility model registration request] In a leakage current measuring device that measures the leakage current of a device under test by applying a voltage between the first and second terminals of a device under test consisting of an electric circuit or an electric element, Therefore, there is a step voltage power supply that outputs a voltage that changes stepwise with respect to a reference potential, and a manual voltage power supply that is equipped with a manual voltage setting means and outputs a voltage that is of a magnitude set in the manual voltage setting means and is relative to the reference potential. A set voltage power supply, an ammeter connected between the second terminal and the reference potential, a voltage follower receiving the voltage of the second terminal, and an output voltage of the voltage follower and the step a voltage adder that adds the output voltage of the voltage power supply; a current booster that amplifies the output current of the voltage adder; and either the output voltage of the current booster or the output voltage of the manually set voltage power supply. A leakage current measuring device comprising: voltage selection means for selecting a voltage according to a voltage selection signal and guiding the voltage to the first terminal; and a controller for outputting the voltage control signal and the voltage selection signal.