Clamp Meters

Current without breaking the circuit. A clamp meter reads the magnetic field around a conductor, so you measure load on a running feeder by opening the jaw around a single conductor - no disconnect, no series connection, no downtime. Jaw size is the first practical limit: it has to close around the conductor, which is why a larger jaw matters on service entrance work and a slim one is easier inside a crowded panel. AC-only models cover most building and utility work; AC/DC models use a Hall effect sensor and are what you need for battery systems, solar and vehicle work where the current does not alternate. True RMS is the specification that matters on anything with a variable speed drive, LED lighting or switching supplies, because an averaging meter reads a distorted waveform low and can have you believe a circuit is comfortably loaded when it is not. Most clamp meters also carry probes for voltage, resistance and continuity, so one instrument covers the common checks. Clamp one conductor only - two cancels the reading.