HT7051 - HT7051N
EN - 32
12 THEORETICAL APPENDIX
12.1 POLARIZATION INDEX (PI)
PI is the ratio of Insulation Resistance values measured after 1 minute and after 10
minutes. The DC test voltage is present during the whole period of the measurement (an
Insulation Resistance measurement is also running). On completion of the test the PI ratio
is displayed
min)1(
min)10(
Rins
Rins
PI
General applicable values:
PI value Insulation conditions
from 1.0 to 1.25 Not acceptable
from 1.4 to 1.6 Good
>1.6 Excellent
12.2 DIELECTRIC ABSORBTION RATIO (DAR)
DAR is ratio of insulation resistance values measured after 30s and after 1 minute. The
DC test voltage is present during the whole period of the test (also an Insulation
Resistance measurement is continually running). At the end, the DAR ratio is displayed:
)30(
min)1(
sRins
Rins
DAR
General applicable values:
DAR value Insulation conditions
< 1.0 Dangerous
from 1.0 to 2.0 Not acceptable
from 2.0 to 4.0 Good
> 4.0 Excellent
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