Insulation Testers

Insulation failures or broken conductors or connections may cause a circuit conductor to contact a grounded surface. These accidental or unplanned faults are often termed "ground faults." When faults aren't obvious, the use of ground fault testers is appropriate.

Ground fault testers, sometimes called insulation testers, should only be used on de-energized circuits. An insulation tester applies a high voltage to a circuit and measures circuit resistance. It will detect circuits or equipment with faulty insulation as well as short circuits. High voltage testers must not be used on low voltage circuits.