The Greenlee CM-450 (52033579) True-RMS AC Clamp Meter, 40/400/600A AC, 600V AC/DC, is a hand-held testing device capable of measuring up to 600 amps of alternating current, in addition to measuring AC or DC voltage, frequency, and resistance. It also checks diodes and verifies continuity. The CM-450 is a true RMS-reading meter.