Clamp meters rely on the principle of magnetic induction to make non-contact AC current measurements. Electric current flowing through a wire produces a magnetic field.

A current transformer inside the clamp meter senses the magnetic fluctuations and converts the value to an AC current reading.

Clamp meters allow electricians to bypass the old-school method of cutting into a wire and inserting a meter's test leads into the circuit to take an in-line current measurement.

The jaws of a clamp meter do not need to touch a conductor during a measurement.