| 摘要 |
PURPOSE:To improve the resonse speed of the detection of an object by connecting a voltage control resistor circuit as a resistor deciding a conductance of an oscillation circuit, amplifying inversely the detection output of the oscillation circuit, controlling the voltage control resistance circuit so as to keep the amplitude of the oscillation circuit nearly constant thereby detecting the object based on the control signal of the voltage control circuit. CONSTITUTION:When an object approaches a proximity switch, an amplitude VL, of the oscillation circuit is lowered slightly, a detection voltage Vd is lowered attended therewith and a control voltage VG is increased remarkably. Thus, the conductance gx of the oscillation circuit is increased from a conductance gx2 into gx1. The position of the object is unchanged. the amplitude of the oscillation circuit is nearly constant and the control voltage VG of a voltage control circuit 23 is changed corresponding to the distance. That is, when the control voltage VG exceeds the threshold value level Vref of a comaprator 9 decided in response to the output level of the control voltage, an object detection output is outputted from an output circuit 10. Thus, the response speed of the proximity switch depends on the response speed of the voltage control circuit 23 to improve the response speed.
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