Inductive proximity sensor - has oscillator in bridge circuit in branch of current source and continuously restores bridge balance

摘要

The inductive proximity sensor has an oscillator module (Z3) containing a coil (L1) which is damped by the presence of an object (6). The module forms a branch (3) of the DC supplied (UB) bridge circuit (1 to 4) such that a resultant voltage change (RV) is evaluated (S) for analogue digital load control via the voltage (VA). A branch (1) of the bridge (1 to 4) contains an impedance (Z1) exactly matched to the oscillator's static impedance (Z3) and of identical thermal construction. An AC source (8) controlled by the evaluation unit(s) continuously restores the bridge (1 to 4) balance with the resultant minimisation of source voltage and thermal errors. USE/ADVANTAGE - Also for analogue path measurement. Has improved accuracy and long-term stability as consequence of thermal compensation and insensitivity to spurious oscillatory influences. Is universally applicable to both analogue and digital systems.