Amprobe AMB-3 Insulation Resistance Tester Insulation resistance meter with built-in voltmeter to test insulation of wires, cables, transformers, and electrical motors Analog meter with manual range selection Power lock to keep power on for multiple tests Measures voltage from 0 to 600V AC/DC and insulation resistance from 0 to 1,000 megaohms with 500V DC test voltage Automatically discharges instrument capacitance for safe removal of test leads