4.2 Displaying PI and DAR
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• The tester automatically calculates and
displays PI (polarization index) and DAR
(dielectric absorption ratio), which are
used as the criteria to determine the qual-
ity of insulation.
Both measurements show a degree of
change in insulation resistance with time
after a test voltage is applied.
Appendix 3 "Example of PI Criteria (Polarization
Index)" (page 162)
• PI and DAR are calculated using the for-
mulae below from resistance values mea-
sured twice after a voltage is applied. For
PI, the measurement interval may be
user-set.
See 6.1 "Changing and Checking Interval Set-
ting for PI Calculation" (page 123).
Procedure
4.2 Displaying PI and DAR
What is it used for?
Used to check whether insulation re-
sistance increases with time after a
voltage is applied.
(When the PI value or the DAR val-
ue is close to 1, the tester deter-
mines that the insulation of the
object under test is deteriorated.)
PI 10/1min =
DAR 1min/15s =
DAR 1min/30s =
To determine DAR, press the key to
turn off [
AVE] on the screen before starting
measurement.
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