Hall Effect clamp meters can measure both ac and dc current up to the kilohertz (1000 Hz) range. Like current transformer types, Hall Effect clamp meters use rigid iron jaws to concentrate the magnetic field that encircles the conductor being measured.

Unlike current transformer clamp meters, the jaws are not wrapped by copper wires. Instead, the magnetic field generated by the conductor is focused across one or more gaps in the core after the jaws are clamped around the conductor. Notice the point where the jaw tips of a Hall Effect clamp meter meet.
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