Insulation resistance testing uses which unit?

Insulation resistance testing uses which unit?

• A. Volts (V)
• B. Ohms (Ω)
• C. Amperes (A)
• D. Megaohms (MΩ)

Answer: (D)

When you test insulation, you’re checking how much current leaks through the insulation when a high DC voltage is applied. The key is that good insulation resists leakage very strongly, so the resistance values are extremely large. Expressing that resistance in ohms would yield numbers in the millions, which is cumbersome, so we use megohms. A megohmmeter is the instrument used for insulation testing and it displays readings in MΩ. In short, insulation resistance testing uses the megohm unit because insulation typically presents very high resistance, and MΩ conveniently communicates those large values.

When you test insulation, you’re checking how much current leaks through the insulation when a high DC voltage is applied. The key is that good insulation resists leakage very strongly, so the resistance values are extremely large. Expressing that resistance in ohms would yield numbers in the millions, which is cumbersome, so we use megohms. A megohmmeter is the instrument used for insulation testing and it displays readings in MΩ. In short, insulation resistance testing uses the megohm unit because insulation typically presents very high resistance, and MΩ conveniently communicates those large values.