AEMC 1000N - Audible Signal; Precautions When Making DC Insulation Tests

Megohmmeter Model 1000N/1100N
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When the PUSH-TO-TEST button is in the ON or LOCK-IN position, an
audible signal will result. This signal consists of approximately one beep
every six seconds (ten beeps per minute). The signal can be used as a
time base for monitoring the duration of the test. On the M
Ω
and G
Ω
ranges, the signal indicates that the instrument is in operation and that
the selected DC test voltage may be present on the terminals of the
instrument.
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•
The equipment should be taken off the line sufficiently in advance to
permit it to cool to ambient temperature.
•
When you are testing windings, they should be clean and dry; let
solvents and cleaners evaporate. Should foreign matter or wet
surfaces be present, erroneous readings may result. (A clean, dry
sample’s resistance may rise for 5 to 15 minutes, whereas a wet, dirty
one will stabilize quickly).
•
Make sure that the equipment tested is properly discharged and
grounded before testing.
•
When testing individual windings, connect all other windings (not
under test) together and ground to motor frame.
•
When testing phases, be sure they are open to test each individually.
•
After applying a test voltage, allow sufficient discharge time. As a rule,
discharge twice as long as tested.
Note:
The instrument voltmeter will indicate the discharge voltage at the
terminals.