PROXIMITY SWITCH

PURPOSE:To provide a solid structure in proximity switch by constituting the proximity switch by use of not a resin case but a metallic case. CONSTITUTION:An nonmagnetic metal body is used as a case 1. In the case 1, a detecting coil 3 is provided on the detecting surface side, and an exciting coil 2 and a detecting coil 4 on the reverse side. The exciting coil 2 is driven at a low frequency, and the detecting coils 3, 4 are connected in series to each other in the direction of mutually canceling the induced voltage when an object is not approached. The voltage difference is detected by a differential amplifying circuit, and a magnetic metal is detected by the increase in differential amplified output based on the access of the magnetic metal.