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.

Clamp meters may provide special measurement types or optional features. Some clamp meters can test diodes or transistors. Others can monitor thermocouples or resistance temperature detector (RTD) values. Programmable clamp meters provide internal data storage and allow users to establish activation triggers. They can also interface with computer hardware and software. In addition, products with external storage devices such as disc drives are available. With regard to optional features, clamp meters may adjust sampling rates automatically, display status information as a bar graph, and measure decibel (dB) readings. Mirrored scales make it easier to read clamp meters to a given accuracy by enabling operators to avoid parallax errors.

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

Clamp Earth Resistance Tester can measure the ground fault which can not be measured by tradition method are unworkable.