Klein Tools MM420 Multimeter is an auto-ranging, true root mean square (TRMS) multimeter that measures AC/DC voltage, AC/DC current, and resistance. It can also measure temperature, capacitance, frequency, duty-cycle, and test diodes and continuity. Klein ToolsÛª Test and Measurement product line was exclusively designed from the ground up by electricians for electricians. Years of field research, combined with extensive input from electricians across America, inspired the development of meters and electrical testers loaded with innovative, time-saving features.