ClampMeter

ClampMeter is a portable electrical instrument designed to measure electrical current in a conductor without disconnecting the circuit. It operates by clamping a hinged jaw around a single conductor; the current in the conductor generates a magnetic field that is sensed by a current transformer inside the device and converted into a readable current value on a digital display. Most ClampMeters are digital multimeters that can also measure voltage, resistance, continuity, and often other quantities such as capacitance, frequency, and temperature. Many models feature true RMS sensing for accurate readings with non-sinusoidal waveforms and offer additional capabilities such as data logging, auto-ranging, backlit display, non-contact voltage detection, and wireless connectivity.

There are handheld versions for general electrical work and larger clamp meters designed for industrial or high-current applications. Jaw openings and the ability to clamp around busbars or multiple conductors vary by model. ClampMeters are used by electricians, technicians, and engineers for troubleshooting, verifying loads, checking fault conditions, and monitoring energy use. They are valued for being non-invasive and for enabling quick current measurements in live circuits.

Limitations include the requirement to measure a single conductor and potential inaccuracies if multiple parallel conductors are enclosed or if the conductor is enclosed within a metal enclosure. Some models only measure AC current unless specified as DC-capable. Safety comes from proper use, insulation, proper CAT rating, and adherence to electrical safety standards.

History: clamp-on current measurement devices were developed in the late 20th century and have since evolved into compact, affordable digital meters widely used in electrical work.