Patent ID: 7423422
Filing Date: 2008-09-09
Classification: G01V

Abstract:
1. A metal detecting apparatus comprising: a signal generator, a transmission coil which receives a signal supplied from said signal generator and causes an alternating field of a frequency equal to a frequency of the signal on a conveyance route of an object of inspection, a magnetic field variation detecting unit which includes two reception coils arranged along the conveyance route in positions to receive said alternating field, and supplies a signal matching a variation in a magnetic field due to the object passing said alternating field, a detector unit which subjects an output signal of said magnetic field variation detecting unit to synchronous detection with a signal of a frequency equal to a signal supplied from said signal generator, determination means which compares an output signal of said detector unit and a threshold to determine presence or absence of any metal contained in the object of inspection, an indicator, and a memory which stores in advance data of signals supplied by said detector unit when a plurality of metallic foreign matter samples differing in magnitude pass said alternating field and data representing magnitude of each foreign matter sample, wherein said determination means displays the detectable magnitude of metal corresponding to the threshold on said indicator on a basis of data on the foreign matter samples stored in said memory.