Which instrument is used to measure insulation resistance between conductors or to ground?

Which instrument is used to measure insulation resistance between conductors or to ground?

• A. A voltmeter measures insulation resistance between conductors or to ground.
• B. A ammeter measures insulation resistance between conductors or to ground.
• C. Megohmmeter measures insulation resistance between conductors or to ground.
• D. A multimeter measures insulation resistance between conductors or to ground.

Answer: (C)

Measuring insulation resistance between conductors or to ground requires applying a high voltage and detecting how little current leaks through the insulation. The instrument designed for this is a megohmmeter (often called a megger). It applies a high DC voltage and measures the leakage current to determine resistance in megohms. A high resistance indicates good insulation, while a lower resistance reveals leakage paths or deterioration. Voltmeter and ammeter only measure voltage or current, not insulation resistance. A standard multimeter can measure resistance but isn’t built for the high voltages and very large resistance values typical of insulation testing, so it isn’t suitable for this purpose.

Measuring insulation resistance between conductors or to ground requires applying a high voltage and detecting how little current leaks through the insulation. The instrument designed for this is a megohmmeter (often called a megger). It applies a high DC voltage and measures the leakage current to determine resistance in megohms. A high resistance indicates good insulation, while a lower resistance reveals leakage paths or deterioration.

Voltmeter and ammeter only measure voltage or current, not insulation resistance. A standard multimeter can measure resistance but isn’t built for the high voltages and very large resistance values typical of insulation testing, so it isn’t suitable for this purpose.