Polarization Index

This diagnostic test recognises the fact that "good" insulation will show a gradually increasing of Insulation Resistance after the test voltage is applied. The Insulation Resistance is measured at two different times: normally at 1 min and 10 min (other time settings are possible). Then the instrument divides later reading by the earlier reading, obtaining the result so called the Polarization Index (PI). PI is dependent on the shape of insulation, influenced by moisture and it does not need to be temperature corrected.