Patent ID: 8158902

Claim:
An apparatus for sorting metal, comprising: a planar surface upon which a plurality of metal pieces are placed, wherein the metal pieces comprise a first size and a second size; a plurality of shielded inductive proximity sensors mounted in close proximity to the planar surface operable to detect metal pieces of the first size but not metal pieces of the second size; a plurality of unshielded inductive proximity sensors mounted in close proximity to the planar surface operable to detect metal pieces of the second size; and a sorting device operable to sort the plurality of metal pieces by the first size and the second size based on information from the plurality of shielded inductive proximity sensors and the plurality of unshielded inductive proximity sensors; wherein at least one of the plurality of shielded inductive proximity detectors operates at a first frequency and another of the plurality of shielded inductive proximity detectors operates at a second frequency or at least one of the plurality of unshielded inductive proximity detectors operates at the a frequency and another of the plurality of unshielded inductive proximity detectors operates at a second frequency.