| 摘要 |
PURPOSE:To realize a proximity switch of magnetic field resistance type by changing an adjusting resistance of an oscillation circuit at the stop of oscillation so as to start the oscillation easily in a proximity switch of high frequency oscillation type. CONSTITUTION:When a high AC magnetic field is applied to the proximity switch, the switch is brought into a state that a proximity sensed body is adhered to a coil 2 resulting that the oscillation is stopped. An output of a smoothing circuit 4 is compared with a reference voltage by a comparator 6, a transistor (Tr)8 is driven by the output, a resistor R9 is connected in parallel with a resistor VR3 for adjusting detection distance and the oscillation is started easily. Thus, the oscillation is started when the circuit condition approaches a zero cross point of the AC magnetic field. Then a signal being at an L level is obtained at each burst oscillation from an output circuit 7. But an output of integration comprising a resistor R10 and a capacitor C11 is not almost increased and no output is given from an output circuit 14. When the proximity sensed body approaches in this case, the circuit cannot oscillate even near the zero cross point of the AC magnetic field. Thus, the output of an output circuit 7 is not decreased to the L level and the output of the integration is increased, then a detection signal from the output circuit 14 is obtained. |
