Fast classification of non-magnetic metal targets using eddy-current based impedance spectroscopy

We present a new method to sort non-magnetic conductive metals - specifically brass, copper and aluminium - with the aim of improving economic yields in the scrap metal and recycling industries. The method uses the impedance spectra of the metal objects derived from the scattered magnetic field. Preliminary results are presented on a small sample set showing good accuracy across all metal classes even when the test objects are travelling at high speeds (1 m/s). The results suggest the method is both feasible and practical at the high-throughput demanded by industry.