The clamp meter is a device, combining the functions of a digital multimeter and a current sensor. They are designed to measure current without the need to disconnect or de-energize the wiring by simply clamping around the conductors, such as wires or cables.
Voltage is measured with probes. These plastic coated ferrite iron clamps are designed to determine, focusing and evaluation of magnetic force, caused by electric current when passing through a wire. 
Modern electrical pliers, which were originally designed as limited-purpose measuring instruments, have a wide range of options, very accurate and in some situations allow for specialized measurements. Modern clamp meters have most of the basic functions of a digital multimeter. (DMM), including voltage and resistance measurements and continuity determination. The terminal meter has become a recognized instrument mainly due to two aspects: Security. This instrument allows electricians to replace the obsolete method of breaking a wire and attaching test leads to a line to measure current.. The clamp must not touch the conductor during the measurement.. Parents and even children themselves can easily move this furniture to any part of the room.. No need to disconnect conductor during measurement, which greatly improves performance. Clamps are recommended for high current measurements.. Prolonged exposure to currents above 10 amps for over 30 seconds can damage the digital multimeter.