A New Type of Superconducting Direct Current Meter for 25 kA

An accurate measurement of direct currents in closed superconducting circuits is often difficult to perform, especially if the circuit is exposed to time dependent and/or high stationary magnetic fields. In this paper a new type of non-contacting direct current meter that can measure large currents (in this case up to 25 kA) with an accuracy of 0.1% of full scale is presented. The device consists of a superconducting toroidal transformer that encloses the unknown current flowing through the aperture, a shielded field sensing coil which is connected to the transformer but positioned in a weak magnetic field, and a control unit that presents a reading of the measured current.