MD-5060
8
•
ABSORPTION INDEX
A
I
: On this test, the megohmmeter should remain on, applying high voltage
to the sample for 1 minute (60 seconds). After this time, the operator must press the “
A
I
” key for
reading the ABSORPTION INDEX value on the display. If he anticipates and press the key before
one minute is elapsed, the display will show
A
I
= ???.
The ABSORPTION INDEX is the ratio between the insulating resistance value measured at 60
seconds' time and the value measured at 30 seconds' time and it is useful for winding preventive
maintenance (on transformers, motors, generators, etc.).
R
60 seconds
A
I
=
R
30 seconds
•
POLARIZATION INDEX
P
I
: On this test, the megohmmeter should remain on, applying high
voltage to the sample for 10 minutes. After this time, the operator must press the “
P
I
” key, so the
megohmmeter
shows the
P
I
value on the display
.. If he anticipates and press the key before 10
passed minutes, the display will show
P
I
= ???. If he presses it after 10 minutes until 15 minutes,
the
P
I
will be shown.
The POLARIZATION INDEX is the ratio between the insulating resistance value measured at 10
minutes' time and the value measured at 1 minute time.
R
10 minutes
P
I
=
R
1 minute
Approximately 5 minutes after the 10 minutes BEEP has sounded, the equipment will turn off
automatically if no new function is selected (no key is pressed or reset).
The POLARIZATION INDEX is useful for preventive maintenance for detecting insulation
resistance degradation due to excessive dust, grease, or action of chemical or physical agents, etc.
