Inductive measurement of the free surface of liquid metals

A novel measurement system to determine the surface position and topology of liquid metals is presented. It is based on the induction of eddy currents by a time-harmonic magnetic field and the subsequent measurement of the resulting secondary magnetic field using gradiometric induction coils. The system is validated experimentally for static and dynamic surfaces of the low-melting liquid metal alloy gallium-indium-tin in a narrow vessel. It is shown that a precision below 1 mm and a time resolution of at least 20 Hz can be achieved.