A megohmmeter is an electrical testing device used to measure the insulation resistance of electrical equipment and wiring. It applies a high voltage, typically between 250 to 1000 volts, to the insulation and measures the resistance in megohms. This helps identify potential insulation failures, ensuring safety and reliability in electrical systems. These devices are commonly used in industries such as construction, manufacturing, and utilities to maintain equipment and prevent electrical hazards. Regular testing with a megohmmeter can help detect moisture, dirt, or deterioration in insulation, which can lead to electrical faults or failures if not addressed.