What is essentially a megger?

A megger, which is short for megohmmeter, functions primarily as a hand-driven DC generator that generates a high voltage to measure the insulation resistance of electrical systems. Its main purpose is to evaluate the integrity of insulation and ensure that it can withstand the operational conditions without failing. By applying a direct current voltage, it can assess the resistance of an insulating material in megohms, which is critical for safety and performance in electrical installations.

This tool is specifically designed to deliver a high potential that can test insulation materials, which allows for the detection of faults, moisture ingress, or degradation in insulation. Its operation requires generating a substantial voltage, typically higher than standard circuits, which makes the hand-driven mechanism important, as it enables users to perform tests in various locations without relying on an external power source.

The other choices suggest different measuring tools—such as a DC generator for voltage measurement, a battery-operated ohmmeter, and a digital voltmeter—which do not capture the unique function of the megger in assessing insulation resistance at high voltages. The distinct characteristic of the megger as a device that carries out insulation resistance testing sets option C apart as the correct answer.