Inductive detection of presence of metallic piece - using oscillating circuit connected to inductance which emits electromagnetic field, and CMOS logic circuit as comparator

摘要

The inductive detection arrangement includes circuits with infinite input impedance and zero output impedance such as operational amplifiers to form an oscillating circuit (1). The oscillator output is fed to a resonant circuit (2) whose inductance emits an em field over a zone which may contain a mobile metallic piece (3). Any reduction in the amplitude of the oscillations caused by resistive losses in the mobile piece (3) is detected by a comparator and differential comparator (7,7'). The signals are made suitable for use by amplifying and isolating stages (12) (13). ADVANTAGE - Equipment enables movement of toothed wheel to be detected.