KYORITSU 3147A - Manual (Page 13)

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<Simplified measurement of DC voltage>
This instrument also provides simplified measurement of DC
voltage. Multiplying 0.9 by the indicated value at AC voltage scale
provides the DC voltage value. However, the polarity isn't
indicated.
DC voltage (V) = Indicated value at AC voltage scale x 0.9 (V)
6−2 Insulation resistance measurement
Before performing any insulation test, check the maximum
voltage that may be applied to the circuit under test.
Note:
¡
Some circuits have an unstable insulation resistance, which
causes the reading to vary during measurement.
¡ The instrument may generate a high pitch tone during
measurement. This is not a failure.
¡ If the circuit under test has a large capacitive load, it may take
some time before the final reading can be obtained.
¡ On insulation resistance range, DC voltage is supplied through
Earth and Line probes, with Earth probe having positive polarity.
Earth probe should be connected to the earth conductor in the
circuit under test. Such connection is known to be more suitable
for insulation tests since an insulation resistance value measured
with the positive side connected to earth is typically less than that
taken through the reversed connection.
DANGER
¡ When the Test button or Remote control switch is pressed
with the Range switch set to an insulation resistance range
position, take care not to touch the tip of the test probe or the
circuit under test where a high voltage is present in order to
avoid possible shock hazard.
¡ Do not make measurement with the Battery cover removed.
CAUTION
Ensure that the circuit under test is de-energized prior to any
insulation testing.