Patent ID: 7102347

Claim:
A metallic contaminant detecting method comprising the steps of: conveying an inspection object contained in a package along a conveyance path to detect a metallic contaminant accidentally mixed in said inspection object during a manufacturing process; and detecting step of detecting the metallic contaminant mixed in said inspection object by generating a magnetic field from a detecting element provided in an intermediate portion of said conveyance path, said detecting element having a coil comprising a core and a conductor wound around said core; generating a small magnetic field by applying a voltage to said coil or supplying an electric current to said coil, and detecting a detection magnetic field generated from said metallic contaminant in response to said small magnetic field as a detection voltage or a detection current of said coil, and then outputting a detection signal; and analyzing said detection signal to identify said metallic contaminant; wherein said small magnetic field is created by applying a small voltage to said coil or supplying a small electric current to said coil and using a non-linear portion of magnetic field characteristics of said core constituting said coil, in which a magnetic field (H) and a magnetic flux density (B) of the non-linear portion are small values of about zero; and said coil operates at a frequency in a range of several hundred Hz to several ten kHz.