Insulation resistance testers are available in various sizes and output voltages, depending on their specific application.

Insulation resistance testers are most commonly referred to as "insulation meters" to determine the insulation status of various types of electrical equipment (such as cables, transformers, and switching equipment).

Usually, the test is performed by applying a direct current (dc) voltage to the conductor under test and measuring the current flowing through the insulating layer (called "leakage current") and flowing into the non-current-carrying metal parts of the device. Insulation pollution can be determined by observing the absorbed current or the current absorbed by the insulation within a certain period of time.

Insulation resistance test data can be used to establish a trend graph, which deviates from the baseline information to assess insulation. The results of these tests (usually expressed in megohms) depend on the temperature of the insulating material and the humidity of the surrounding environment during the test. Therefore, all readings must be corrected to the reference temperature, for example 20°C.

How much voltage can be generated?

Insulation resistance testers are available in various sizes and output voltages, depending on their specific application. Hand-held 1000V dynamometers are usually sufficient to meet the needs of 600V class equipment, while large equipment used for high-voltage equipment can output voltages up to 15,000V or higher.

Insulation resistance tester test connection

There are three test terminals on the insulation resistance tester, marked as positive (+), negative (-) and protection (G). Most basic measurements use only positive and negative terminals, for example, when there are few adverse current paths that may affect the results.

When testing at higher voltages, such as using cables or transformers, the protective terminals can be used to divert the surface leakage of the measurement circuit. Not all insulation resistance testers are equipped with protective terminals.