| 摘要 |
<p>PROBLEM TO BE SOLVED: To precisely detect a metal piece even if it is in a different use environment by regulating amplitude of a resonant signal, so that detection voltage becomes the value immediately before output of a comparison result which indicates presence of the metal piece from a comparison circuit. SOLUTION: Amplitude of a resonant signal from a resonant circuit 1 in the case in which a metal piece is not close to a detector 2 by a sensitivity regulation means 3 such as a variable resistor provided in the resonant circuit 1. The amplitude of the resonant signal is regulated with the sensitivity regulation means 3 so that a difference between threshold value voltage Vs1 and detection voltage Vd in the case in which the metal piece is not close thereto is smaller from the point of view in which the threshold value voltage Vs1 compares presence and absence of the smallest metal piece or the most detection distant metal piece with each other. A comparator 51 or LED 63 for showing its comparison result is utilized, and the amplitude of the resonant signal is regulated to the value shown immediately before LED 63 is lighted as the comparison result, in response to the presence of the metal piece.</p> |
