Proximity switch triggered by approach of human nand - has capacitive and inductive sensors combined into one coil in pot-shaped core

摘要

The proximity switch has a capacitive probe connected to a capacitance measuring circuit which delivers a switching when the capacitance increases by a given amount. An oscillator fed inductive probe responds to the presence of metal objects. The oscillator coil that forms the inductive sensor (3, 4) or a part of this oscillator coil, is also used as the capacitive probe. That part (3a) of the coil acting as capacitive sensor is considerably larger than the rest (3b) of the coil. The coil (3) is located in a pot-shaped core (7). The smaller part (3b) of the coil is inside or outside the larger part or beneath it on the bottom of the core.