TENTECH MD-5075x, User Manual, Page: 22 / 69

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7.2. Measurement of the Polarization Index (PI)
When pressing the key during the test, the Polarization Index (PI)
value will be exhibited on the display. It is only possible to apply this
function after a minimum of 10 minutes of measurement; in case the key
is pressed before this minimum limit, the display will show the message of
value exhibition of PI value, but will not show any value.
The polarization index is the quotient between the values of the insulation
resistance measured both in 10 minutes and 1 minute. This index is
useful to detect the damage of the insulation resistance by the excessive
presence of dust, dirt and greases or through the action of chemical and
physical agents.
=
PI
R
R
10 minutes
1 minute