Megger BMM2500 Guide De L'utilisateur page 9

Good procedure whilst Insulation Testing
Care must be taken when taking measurements
greater than a few GΩ. 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 SP1 is not used as the accuracy at
high value measurements is not guaranteed. The
instrument should also be clean and dry with par-
ticular 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 (P I) is the term applied to the
Dielectric Absorption Ratio when resistance values
a re measured after 1 minute and again after 10 min-
utes. 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.
M o re detailed information on P I Testing and value
assessment can be found in AVO International pub-
lications listed in the Accessories page.
8
Automatic Discharge
When the TEST button is released after an insula-
tion test (or re-pressed if ltb feature is enabled), a
200kΩ 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