Insulation Resistance

The insulation resistance function can be found in several Vitrek electrical safety testers: the V53, V4 and 944i.

Insulation resistance measurement is generally conducted to determine the quality level of electrical insulation. As opposed to a hipot test, where one is normally checking for insulation failure or breakdown, the insulation resistance test is an ohmic measurement of the electrical resistance of the insulation. Electrical insulation is usually expressed in meg ohms or gig ohms. Often the test requirement will specify a DC voltage that will be applied (typically 500 or 1000VDC), the duration of the test and a minimum value for the insulation resistance.

There are several common insulation resistance test formats. The decision to pass or fail the insulation resistance test the device under test can be made in a variety of ways. Some insulation resistance tests specify that once the voltage is applied, any readings below the minimum insulation resistance value constitute an immediate failure. This format is referred to as “stop on failure”. Another common insulation resistance test format allows the resistance level to be below the minimum initially and terminates the test with a pass as soon as a reading above the minimum level is obtained. This format is referred to as “stop on pass”. The third most common format requires that the test time elapse and the pass fail decision criteria is based on the final reading.