| 摘要 |
<p>PROBLEM TO BE SOLVED: To make easily contractible an induction access detector for using it as a detector for iron or nonferrous metals. SOLUTION: The induction access detector is constituted to detect objects of iron or a nonferrous metal. An oscillator 12 outputs a constant frequency when a metal object is made to access and this frequency oscillates an oscillation circuit 11 which is not reactive to this metal object at significantly lower frequency than the critical natural frequency of the oscillation circuit. Oscillation signals S1 and S2 are added to the two input terminals of a phase detector 15 and since these signals can be switched by an inverter device 17, the detector can be constituted in iron mode or nonferrous mode.</p> |
