IDEAL 61-797 Manuel D'instructions page 10

When the measured resistance is higher than the maximum range, the
screen will display "Err" symbol for PI/DAR value.
TEST button : Press once to start/interrupt the PI /DAR test.
Blue button : Use to display and check the time left of the PI/DAR test.
The measured values of PI test
PI = R10-min/R1-min
The measured values of DAR test
DAR = R1-min/R30-sec
If the reading for DAR is bigger than 1.3 or PI is bigger than 2, it indicates
that the insulation is good. On many installations, the quality of the
insulation is so good that both the initial measured value and the
subsequently measured value (when performing the PI or DAR tests),
will be the maxium that the meter can read. Dividing one into the other
will of course read the value of 1, which in this case may be perfectly
good. It is strongly recommended that in all cases, you contact
the manufacturer of the device under test or the appropriate
manual, to ensure that any reading meets the manufacturers
specification for determining if a part is good or bad.
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