Inductive proximity switch with externally activated oscillator - has compensation coil in series-opposition to oscillator indicator coil

摘要

The proximity switch has an externally actuated inductive presence indicator, such as an oscillator, behind which a switching amplifier is incorporated. The oscillator controls an electronic switch, e.g. a transistor, a thyristor, or a triac, via the switching amplifier. The oscillator contains an indicator impedance with an indicator coil and respective ferrite core. In series opposition to the indicator coil (2) a compensation coil (5) is connected that shares the ferrite core with the indicator coil. Pref. the ferrite core is dish shaped the two coils being fitted within the core. The indicator coil may be secured to the open side of the core, while the compensation coil is set below the indicator coil. ADVANTAGE - Increased independence from external fields which could saturate the ferrite core.