A Current Clamp Probe or CT is a transformer converting the large current in the conductor to a smaller current for safely measuring by the power quality analyser. The jaws of typical current clamp are made of a ferromagnetic material such as iron with the secondary winding wound around. The primary winding is a conductor around which the probe jaws are closed, hence most often it is one single coil. If the 1000-ampere current flows through the tested conductor, in the secondary winding with 1000 coils the current will be only 1 A (if the circuit is closed). In case of probes with voltage output, a shunt resistor is located in the probes.
How does a current clamp work?