KYORITSU 3123A - Manual (Page 8)

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4-3. Insulation Resistance Measurement
With the function switch set at OFF position, always connect the
circuit under test to earth. Attach the test lead to the earth terminal
of the instrument and connect to the earthed side of the circuit
under test. With the function switch set at 2500V and 5000V for
KEW 3121A and 3122A or 5000V or 10000V for KEW 3123A,
place the line probe in contact with the circuit under test and
operate the press to test button. When the green LED illuminates,
read insulation resistance on the outer scale (for high range). Use
the inner scale where the red LED illuminates. For insulation testing
at 5000V and 10000V, read the black and red scales respectively
(for KEW 3123A). After a test, release the press to test button and
wait for several seconds without disconnecting the line probe from
the circuit tested. This is intended to discharge the charge stored in
the circuit tested.
4-4. Continuous Measurement
Make sure that the circuit under test is earthed and that the test
lead attached to the earth terminal of the instrument is connected
to the earthed side of the circuit under test. Push the press to test
button and turn clockwise to lock for continuous measurement.
When making this measurement, good care must be taken against
the high voltage continuously present across the line and earth
terminals of the instrument.
Note: Make certain that the circuit under test does not
include components which will be damaged by the
high voltage applied.