| 摘要 |
<p>PURPOSE:To perform detection of a metallic substance without varying the intensity of oscillation while maintaining the condition of oscillation to be stable, by a method wherein a variation in the amplitude of oscillation due to a variation in Q of a coil for detecting the metallic substance is fed back to an oscillator circuit. CONSTITUTION:A variation in the amplitude of oscillation of an oscillator circuit 5 caused by a variation in Q of a coil 1 due to the approach of a metallic substance is inputted to a feedback circuit 8 through an amplifier circuit 6 and a detector circuit 7. Moreover, the variation is fed back to a variable capacity element 4 which is a capacitance of the oscillator circuit 5, so as to vary the capacitance of LC oscillation, a variation in an oscillation frequency on the occasion is detected from the component of the oscillation frequency inputted to an input terminal 91 of a frequency variation detector circuit 9, and based on this detection, a signal of detection of the metal is delivered from an output terminal 92. By this method, the amplitude of oscillation can be maintained invariable even when the metallic substance approaches, and the detection of said substance can be performed without impairing the stability of oscillation.</p> |
