TOS8870A
OPERATION PROCEDURE
17
3.3 Single Insulation Resistance Test
1)
Selecting the insulation resistance test mode
1.
Select the MANUAL IR test mode with the FUNCTION selector switches.
2.
The IR TEST indicator lamp will illuminate. Letter "IR" stand insulation resistance
test.
2)
Check the Zero-ohm
1.
Check that the TIMER ON/OFF switch is in the OFF state.
2.
Short the high voltage test leadwire (hot line) to the LOW test leadwire to make
sure that no high voltage is being delivered to the output terminal.
3.
Press the STOP switch with a state of 2.
4.
Press the START switch with a state of 2.
5.
Check the ohmmeter will indicate approximately zero ohms.
3)
Selecting a test voltage
With the RANGE 500V/1000V switch, select the test voltage of the DUT as required of stan-
dards, and other.
4)
Setting the PASS-FAIL judgement reference values for Insulation
resistance test
The PASS-FAIL judgement by the Tester is done in a window comparator system such that
the PASS judgement is made only when the measured insulation resistance is between the
high and low limit reference values. The FAIL judgement is made not only when the mea-
sured value is lower than the low limit reference value but also when it is higher than the high
limit reference value.
Detection high insulation resistances
The window comparator system is especially advantageous when the distribution of the insu-
lation resistances of DUT can be predicted and the predicted high limit value is in the range of
the detectable resistance of the Tester. To test such DUT, the high limit reference value may
be set at a value slightly higher than the predicted highest value of the DUT, and the test may
be made in the window comparator system. When this is done, DUT of exceptionally high
insulation resistances can be identi
fi
ed and open-circuiting of leadwires and imperfect con-
tacting also can be detected, thereby attaining still better insulation resistance test.
With the REFERENCE SET switches set in the regular state (
), the ohmmeter indicates
the measured resistance when in the insulation resistance test. When not in the insulation
resistance test, the ohmmeter indicates the
∞
position.
A selection and setting of judgment reference value
Press the LOWER REFERENCE SET switch, and the ohmmeter will indicate the low limit
reference value. Next, press the UPPER REFERENCE SET switch, and the ohmmeter will
indicate the high limit reference value. When the two switches are pressed at the same time,
the LOWER REFERENCE SET switch has a priority.
The high and low limit reference values can be set with the potentiometers located at right and
left of the switches. Set the values as required by the DUT. (To make a setting, press down the
resistor with the trimming screw driver and then turn it.)
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