4.2 Displaying PI and DAR
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• The instrument automatically calculates and displays PI
(polarization index) and DAR (dielectric absorption ratio),
which are used as the criteria to determine the quality of
insulation.
Both measurements show a degree of change in insula-
tion resistance with time after a test voltage is applied.
Appendix 3 "Example of PI Criteria (Polarization Index)" (page 164)
• PI and DAR are calculated using the formulae below from
resistance values measured twice after a voltage is
applied. For PI, the measurement interval may be user-
set.
See 6.1 "Changing and Checking Interval Setting for PI Calculation"
(page 125).
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 instrument de-
termines 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.
Resistance 10 min. after voltage application
Resistance 1 min. after voltage application
Resistance 1 min. after voltage application
Resistance 15 sec. after voltage application
Resistance 1 min. after voltage application
Resistance 30 sec. after voltage application
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