Klein Tools MM420 Multi-meter is an auto-ranging, true root mean square (TRMS) multi-meter 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 Tools 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.