How a clamping meter works
A clamp meter, also called a clamp ground resistance meter, is an electrical tester with a wide jaw that clamps onto electrical conductors. Originally designed as a specialized tool for measuring AC current, clamp meters now include inputs for accepting test leads and other probes that support a wide range of electrical measurements. The jaws of the pliers, essential as testing tools, facilitate working in tight spaces and allow current measurements to be made on live conductors without interrupting the circuit.
Although clamp meters are closely related to multimeters, they are not simply multimeters with inductive clamps in place of test leads. Generally, a multimeter can be regarded as a voltage measuring instrument with certain current measurement capabilities, while a clamp meter is a current measuring instrument with certain voltage measurement capabilities.
Clamp meter technology
Clamp meters rely on the principle of magnetic induction for non-contact AC current measurement. Electric current flowing through a wire creates a magnetic field. Because alternating current often reverses polarity, it causes dynamic fluctuations in the magnetic field that are proportional to the current. The current transformer in the clamp meter senses the electromagnetic fluctuations and converts them into AC current readings. This type of measurement is ideal for measuring very large AC currents.
However, direct current flows through a conductor with a fixed polarity. Therefore, the magnetic field around the conductor does not change and a conventional clamp meter will not show any reading. DC clamp meters work based on the Hall effect principle. Hall effect sensors sense a magnetic field caused by an electric current, which produces a small voltage across the Hall effect sensor. The voltage, which is proportional to the current, is then amplified and measured.
Clamp meters often include other sensors such as voltmeters, ohmmeters, etc., which add to the versatility of the instrument. These other sensors use test leads that plug into the clamp meter. Since only clips can be used
