What is clamb meter ?

The clamp meter is an instrument that can measure the alternating current in the ampere range with out having to open the circuit.
The loop is opened by squeesing the "trigger"; then its placed around the current-carrying conductor.
Through transformer action, the level of current in rms units appears on the appropriate scale.
Types of current clamp:

•  Current transformer.

The most common form of current clamp comprises a split ferrite ring. A wire coil is wound around one or both halves, forming the secondary winding of a current transformer. The conductors to be measured forms the primary. Like any transformer this type works only with AC or pulse waveforms.

• Iron vane.

In the iron vane type, the magnetic flux in the core directly affects a moving iron vane, allowing both AC and DC to be measured, and gives a true RMS value of non-sinusoidal AC waveforms. Due to its physical size it is generally limited to power transmission frequencies up to around 100Hz.

• Hall effect.

The hall effect type is more sensitive and is able to measure both DC and AC, in some examples up to the kiloherts range. This type is often used with oscilloscopes, and with high-end computerized digital multimeters.


Clamp meters are used in some meters to measure electrical power and energy. The clamp measures the current and other circuitry the voltage; the true power is the product of the instantaneous voltage and current integrated over a cycle.
Comprehensive meters designed to measure many parameters of electrical energy like power factor, phase relationships, etc.