Which instrument applies high DC voltage to measure insulation resistance for preventive maintenance?

Which instrument applies high DC voltage to measure insulation resistance for preventive maintenance?

• A. DMM measures DC/AC voltage, current, resistance.
• B. Insulation resistance tester measures AC current.
• C. DMM is used for preventive maintenance.
• D. Insulation resistance tester applies high DC voltage to measure insulation resistance.

Answer: (D)

Measuring insulation health in preventive maintenance requires an instrument that can apply a defined high DC voltage to the equipment’s insulation and measure the resulting leakage to determine insulation resistance. An insulation resistance tester, also called a megohmmeter, does exactly this: it charges the insulation with a high DC voltage and reports the resistance in megohms. The higher the resistance, the better the insulation condition; lower readings flag moisture, contamination, or deterioration that could lead to faults. A digital multimeter can measure resistance but at low voltages and it’s not designed for the dedicated insulation-resistance test. Measuring AC current isn’t how this test is performed, and saying a DMM is used for preventive maintenance is too vague to capture the specific purpose of measuring insulation resistance with high DC voltage.

Measuring insulation health in preventive maintenance requires an instrument that can apply a defined high DC voltage to the equipment’s insulation and measure the resulting leakage to determine insulation resistance. An insulation resistance tester, also called a megohmmeter, does exactly this: it charges the insulation with a high DC voltage and reports the resistance in megohms. The higher the resistance, the better the insulation condition; lower readings flag moisture, contamination, or deterioration that could lead to faults. A digital multimeter can measure resistance but at low voltages and it’s not designed for the dedicated insulation-resistance test. Measuring AC current isn’t how this test is performed, and saying a DMM is used for preventive maintenance is too vague to capture the specific purpose of measuring insulation resistance with high DC voltage.