Vanguard IRM-5000P - Manual (Page 31)

REV 2 IRM-5000P USER’S MANUAL
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Figure 8. Polarization Index Test Resistance Plot
Figure 9. Polarization Index Test Current Plot
Table 4. PI Ratio Table
PI Ratio Insulation Condition
Less than 1.0 Unsatisfactory
1.0 to 2.0 Questionable *
2.0 to 4.0 Good
Above 4.0 Very Good **
* A PI ratio between 1.0 and 2.0 is satisfactory for a load with low capacitance, such as short runs.
** A dry, brittle insulation may show a good PI reading but may fail under shock conditions.