What is a megger?

• A. A test instrument used to test insulation of a circuit or component.
• B. A device that measures temperature.
• C. A device that tests continuity.
• D. A device that measures voltage.

Answer: (A)

A megger is a high-voltage insulation resistance tester. It applies a steady DC voltage to the insulation of a circuit or component and measures the leakage current, giving insulation resistance in megohms. The higher the megohm reading, the better the insulation; a low reading indicates insulation degradation, moisture, or contamination that could allow dangerous leakage. It’s specifically for assessing insulation, not for measuring temperature, continuity, or voltage. In practice, you isolate the equipment, discharge any stored energy, select the appropriate test voltage, connect the test leads, perform the test, and compare the reading to acceptable values to determine if the insulation is in good condition or needs repair or drying.