To measure the insulation resistance between heating cable conductors and metallic grounding, which device is used?

The correct device used to measure the insulation resistance between heating cable conductors and metallic grounding is a megohmmeter. This specialized instrument is designed to apply a high voltage (typically 500V to 1000V) to the insulation and measure the resistance in megohms. It is particularly effective for assessing the quality of insulation, as it can identify breakdowns or weaknesses in the insulation that a standard multimeter or ohmmeter would not effectively detect.

A multimeter, while versatile and capable of measuring voltage, current, and resistance, does not provide the high voltage needed for insulation testing. An ammeter measures current flow and is not applicable for insulation resistance tests. An ohmmeter can measure resistance but often does so at low voltage levels, which may not sufficiently stress the insulation to reveal potential failures. Therefore, using a megohmmeter ensures accurate measurements of insulation resistance, making it the ideal instrument for this specific application.