| 摘要 |
<p>PURPOSE: To obtain a proximity switch which can be manufactured at a low cost, has a large size as compared with the diameter of its coil, and has a constant response distance over a wide temperature range. CONSTITUTION: In this proximity switch provided with an oscillator 1 having a transmission coil 2 which vibrates and generates an alternating magnetic field when a trigger body intrudes into the coil 2 and an evaluation circuit 8 which forms a switching signal upon detecting the vibrating state of the coil 2, sensor coils 12 and 13 are provided in a difference forming circuit which detects the difference between voltages U1 and U2 induced in the sensor coils 12 and 13 in the alternating magnetic field and the sensor coils 12 and 13 are constituted so that the difference alternating voltage UD can become zero at a desired response distance depending upon the mutual spatial position and number of turns of the coils 12 and 13. When UD=0, the UD is supplied to the input side 16 of an oscillator amplifier 7 so that the oscillator 1 can change the vibrating state of the coil 2 by leaps and bounds.</p> |
