| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect a magnetic substance and a non-magnetic substance through simple measurement at low cost while keeping almost the same distance by controlling a current through a main oscillator and providing an in-phase oscillated current, whose frequency is equal to that of main wave. SOLUTION: A main oscillator 16 provided in a proximity detector supplies the oscillated signal of a decided frequency. That frequency is not changed even when the metal object gets closer or away. The oscillated signal, which is provided at an output terminal A of this main oscillator 16, to divide the frequency for providing a desired frequency level F is supplied to a control input terminal 17 of current source 18 for supplying an oscillator 10 for exciting an LC parallel resonant circuit 11 of a oscillator 10. Besides, a frequency tuner circuit 19 is provided for regulating the frequency peculiar to the parallel resonance circuit 11 to the frequency of main oscillator 16 when no metal object exists. Then, the current source 18 is controlled by the main oscillator and the in-phase oscillated current, whose frequency is equal to that of the main wave, is supplied.</p> |
