What is the best device to check the condition of cable insulation?

The best device to check the condition of cable insulation is the megger, which is specifically designed for measuring insulation resistance. A megger applies a high DC voltage to the cable and measures the resistance of the insulation, providing a clear indication of its condition. This high-voltage testing is essential because it can identify weaknesses in the insulation that might not be detectable at lower voltages.

The megger's ability to provide precise readings of insulation resistance helps to ensure the safety and reliability of electrical systems. It's particularly effective in determining whether insulation has degraded due to moisture, contamination, or age, making it crucial for maintenance and safety evaluations of electrical installations.

While other devices like multimeters or clamp meters have their uses in electrical testing, they are not specifically designed for insulation resistance testing and may not provide the necessary high voltage required for a thorough examination. An insulation resistance tester is closer to the function of a megger, but the term "megger" is often used generically in the industry to refer to insulation testers, underlining its prominence for this particular application.