| 摘要 |
<p>PURPOSE:To keep the detecting sensitivity of metal constant automatically even if the conveying speed of a material under inspection is fluctuated. CONSTITUTION:An oscillating coil 2 is excited with a high-frequency oscillator 1 so as to generate the alternating magnetic field. The signal obtained from a receiving coil 3, which is interlinked with the magnetic flux of the magnetic field, is detected. The metal of a material under inspection 11, which passes between the oscillating coil 2 and the receiving coil 3, is detected based on the outputted signal obtained through a filter. The filter is a filter circuit 12, whose passing-frequency band can be changed. A speed detector 13 detects the conveying speed of the material under inspection 11 passing between the oscillating coil 2 and the receiving coil 3. A filter control circuit 14 changes the passing-frequency band of the filter circuit 12 in response to the conveying speed of the material under inspection 11 based on the speed signal from the speed detector 13. These parts are provided.</p> |
