What is a Rogowski coil? Here are some definitions.
Noun
An electricaldevice for measuring alternating current (AC) or high-speed current pulses. It consists of a helicalcoil of wire with the lead from one end returning through the centre of the coil to the other end, so that both terminals are at the same end of the coil. The whole assembly is then wrapped around the straight conductor whose current is to be measured.