Analysis and design of ferrite cores for eddy-current-killed oscillator inductive proximity sensors

Finite element modeling of ferrite cores used in the design of eddy-current-killed oscillator inductive proximity sensors was performed. Based on contemplation of the practical operation of the sensors, ferrite core geometries were compared with a reference core by the eddy-current power loss in a metal target at a fixed distance from the face of each transducer. Several of these cores were experimentally evaluated for sensing distance to verify the results of the simulation. It was observed that, for fixed coil, fixed target distance, and given target, the low-frequency sensing distance of a particular transducer is approximately proportional to the fourth root of eddy-current power loss in the target.