Insulation resistance tester, commonly known as megohmmeter or shake table, is a precision instrument specifically used to measure the insulation resistance of electrical equipment, lines, or materials. It calculates the insulation resistance value by applying a stable DC high voltage to the tested object and measuring the resulting leakage current. It is a key tool for determining whether the insulation performance of electrical equipment is good, and whether there are defects such as moisture, aging, or breakdown.