HT Instruments HT4022 TRMS AC Clamp Meter. HT4022 is a clamp meter that performs TRMS measurement of AC current up to 400A, AC/DC voltage, frequency, resistance and continuity. This model also perform measures of Active, Reactive, Apparent power, Power Factor (cosphi), Energy, Voltage/Current harmonics, both in single phase and three phase systems and have a patented phase rotation measures with an innovative one wire method. Thanks to the practical rubber cap to be mounted on the jaws (patented also), it's possible to hold test leads while measuring and have one hand free to work. The large 4 digit LCD display (10000 counts) with backlight permits an easy readability also in critical visual conditions. The instrument is complying with IEC/ EN61010-1, CAT III 600V and is ideal to solve typical problems occurring in industrial environments such as troubleshooting, non-linear loads, frequency driven motors, PCs.