Clamp meters are ammeters that can measure current without the need to disconnect the wires where the measurement occurs. They provide information about current draw and current continuity in order to help users troubleshoot erratic loads and trends. Clamp meters have both positive and negative leads and feature extremely low internal resistance. They are connected in series with a circuit so that current flow passes through the meter. High current flow may indicate a short circuit, an unintentional ground, or a defective component. Low current flow may indicate high resistance or poor current flow within the circuit.

There are two basic types of clamp meters: digital and analog. Both are designed to measure levels of alternating current (AC) and direct current (DC). Some clamp meters that measure AC current also measure root mean square (RMS) power, which is the square root of the time average of the square of the instantaneous power. Most products include a current sensor built into the clamp around the wire. Different types of clamp meters can measure different ranges of AC current, DC current, and AC current frequency. Some clamp meters are handheld and portable. Others are designed for bench top or shop floor use. Battery-powered clamp meters can be operated without plug-in power and may be rated for outdoor use.

Widely applied in ground resistance measurement in field such as electric power, telecommunications, meteorology, oil filed, architecture and industrial electrical equipment.

When measuring ground system with loop, there is no need to disconnect the ground wire without auxiliary electrode, which means safer and faster.