| 摘要 |
<p>PURPOSE:To judge the presence and type of metal by detecting the pattern of a voltage difference induced in both coils when two coils consisting of a plurality of twisted wires are connected differentially and then a metal sample is inserted into the coils. CONSTITUTION:Coils 6 and 7 using a twisted wire consisting of two conductors are provided on a bobbin 22 with a spacing L. Edges 9a and 11a of conductors 9 and 11 of the coils 6 and 7 are connected, similarly other edges 9b and 11a are connected, and then excitation is performed by an AC signal source 4. Also, edges 8b and 10b of the conductors 8 and 10 of the coils 6 and 7 are connected and other edges 8a and 10a are connected to the input terminals of a differential amplifier 16. When a metal sample 5 is inserted into the coils 6 and 7, a difference is generated in the voltage induced at the conductors 8 and 10, current corresponding to the voltage difference flows to the conductors 8 and 10, the voltage difference is detected by the amplifier 16, and then a specific voltage value is output by a rectifier 18. Therefore, the type of the sample 5 can be discriminated by discriminating the output pattern of the rectifier 18 using a detection circuit 19.</p> |
