What device is used to test insulation?

The correct choice, a mega ohm meter, is specifically designed for testing insulation resistance in electrical systems. This device applies a high voltage to the insulation and measures the resistance to determine if there are any weaknesses or failures in the insulation material. By assessing insulation resistance, electricians can identify potential hazards, such as degraded insulation, which may lead to short circuits or electrical failures.

A multimeter is a versatile tool that can measure voltage, current, and resistance, but it is not optimized for insulation testing, particularly at the high voltages needed for accurate insulation resistance assessment. A clamp meter is primarily used to measure current flow in a conductor without direct contact and does not measure resistance. An ohmmeter measures resistance but does so at low voltages that are not suitable for testing the integrity of insulation, making it ineffective for that specific purpose. Therefore, the mega ohm meter stands out as the appropriate tool for effectively testing insulation resistance.