8
Good procedure whilst Insulation Testing
Care must be taken when taking measurements
greater than a few G
Ω
. The leads must be clean
dry and in good condition. They must also not be
allowed to tangle. It is also advisable that the
switched probe SP6F is not used as the accuracy
at high value measurements is not guaranteed. The
instrument should also be clean and dry with
particular attention paid to the terminals. Also
attempt to reduce any leakage that may give
erroneous results on the item under test.
Polarisation Index Testing
Polarization Index (
PI
) is the term applied to the
Dielectric Absorption Ratio when resistance values
are measured after 1 minute and again after 10
minutes. Polarization Index is then the resistance
value after 10 minutes divided by the resistance
value after 1 minute. The test can be run at any
voltage. More detailed information on
PI
Testing and
value assessment can be found in Megger Limited
publications listed in the Accessories page.
Automatic Discharge
When the
TEST
button is released after an
insulation test (or re-pressed if
ltb
feature is
enabled), a 200k
Ω
load is automatically switched
across the terminals to discharge the item under
test. Any voltage present will be indicated on the
display so that the discharge can be monitored.
Typical Terminal Voltage Characteristics
