The Mac Tools Insulation Testing Multimeter, No. EM680, helps find leaks on high voltage components by applying high voltage/low amperage current through a circuit. The circuit is susceptible to "leaking" through the insulation if compromised. This "leaked" current can be detected and addressed accordingly. It can test from 0.1 to 4,000 mega ohms at 250V, 500V or 1000V. The volt meter ranges from 0 to 600V, the amp meter ranges from 0 to 400mA, and the ohm meter ranges from 0 to 40 ohms. The Insulation Testing Multimeter has a IEC-61010 CATIII 600V rating.