| 摘要 |
PURPOSE:To improve the reply speed of object detection by connecting a voltage control resistive element in parallel with a resistor deciding a conductance of an oscillation circuit, amplifying inversely the detection output of the oscillation circuit to control the voltage control resistive element thereby keeping the oscillation with a prescribed small amplitude even when the object approaches. CONSTITUTION:When an object approaches the proximity switch nearer than a distance l2, the circuitry is controlled so that a conductance gx of an oscillation circuit follows a conductance ga of a resonance circuit due to the reduction in a detection voltage Vd and the oscillation is continued at nearly a constant amplitude. Then the approaching body is detected by using a prescribed value Vref being a value Vd2 or over as to the detection output Vd as a threshold level of a comparator 9. Even when the object approaches nearer than the distance l2, the amplitude of oscillation is expanded from a prescribed amplitude level. Thus, the leading of the amplitude of the oscillation circuit is quickened, the level reaches a level detecting the approach of the object in a very short time and the response speed of thc proximity switch is improved remarkably.
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