The design of a ferrite-cored probe

The Eddy current principle has been widely used for measuring coating thickness and the physical properties of materials. Most publications on the Eddy current method are directed towards air-cored coils operated at high frequency on non-ferrous metals. The benefit of ferrite-cored probes has seen little attention. Ferrite-cored probes provide the advantage of enhanced signal-to-noise ratio and increased resolution for electronic detection, which is of importance for measurements taken on unsaturated ferromagnetic substrates. This paper describes the design and development of a novel ferrite-cored probe, which includes the selection of ferrite material, the design of the probe structure and core. Probe core loss and sheared permeability have been investigated and overall probe uncertainties have also been discussed and used to develop a measurement methodology.