Rogowski coil

[1][2][3] Since the voltage that is induced in the coil is proportional to the rate of change (derivative) of current in the straight conductor, the output of the Rogowski coil is usually connected to an electrical (or electronic) integrator circuit to provide an output signal that is proportional to the current.

[2] It can also be made "self integrating" (e.g., no external circuit) by placing a low inductance resistor in parallel with the output.

Rogowski coils are used for current monitoring in precision welding systems, arc melting furnaces, or electromagnetic launchers.

The inductance of a toroid is[8] A device similar to the Rogowski coil was described by Arthur Prince Chattock of Bristol University in 1887.

[11] These sensors share the principles of a Rogowski coil, measuring the rate of change of current using a transformer with no magnetic core.

The main advantage of the planar Rogowski current sensor is that the coil winding precision that is a requirement for accuracy can be achieved using low-cost printed circuit board manufacturing.

A Rogowski coil is a toroid of wire used to measure an alternating current I ( t ) through a cable encircled by the toroid. The picture shows a Rogowski coil encircling a current-carrying cable. The output of the coil, v ( t ) , is connected to a lossy integrator circuit to obtain a voltage V out ( t ) that is proportional to I ( t ) .
Example waveform of RC output for switched-mode load . As explained above, the output waveform CH4 (green) represents the derivative of the current waveform CH2 (blue); CH1 (yellow) is 230 V AC mains waveform