Insulation Resistance Tester, commonly known as Megohmmeter, Shake Table (early hand-cranked type) or High Resistance Meter, is the most basic and important instrument in power systems and electrical engineering for measuring the resistance value of insulating materials such as electrical equipment, cables, and motor windings. Its core function is to evaluate the insulation performance of insulating materials, determine whether the equipment is damp, aged, dirty, or has penetrating defects, thereby preventing leakage and short-circuit accidents. 1. Core Working Principle Unlike ordinary multimeters, the insulation resistance tester integrates a high-voltage DC generator inside. Pressurization: It applies a stable high-voltage DC to the tested object (common levels are 250V, 500V, 1000V, 2500V, 5000V, or even 10kV). Measurement: Under the high voltage, it measures the weak leakage current flowing through the insulating material (usually in microamperes