| 摘要 |
<p>PURPOSE:To detect a passage timing of an object to be inspected without use of light projecting/receiving device in a metal detector which judges the presence of metal mixed into the object to be inspected based on a change in a magnetic field generated in a passage path of the object to be inspected. CONSTITUTION:A detection waveform as obtained when an object to be inspected passes through a magnetic field to be generated from a transmission coil 24 is stored into a detection waveform memory means 33. When the object to be inspected is determined to a rejection by a level judging means 4, a object to be inspected passage timing detecting section 35 subtracts a waveform of an acceptable product stored previously in an acceptable product waveform memory 37 from a detection waveform stored in a detection waveform memory means 33 to judge symmetry of the waveform subtracted. Thus, a timing is detected at which mixed metal passes the boundary position s of receiving coils 25 and 26.</p> |
