Inductive proximity sensor for detecting magnetic and non-magnetic metallic objects

An inductive proximity detector for the detection of magnetic and non-magnetic metallic objects including:

• an analogue oscillator provided with an LC oscillating circuit and powered by a current source (18), the oscillator being arranged to translate the approach of an object into an analogue variation of a quantity characteristic of the oscillation, including its amplitude,
• a circuit for processing the oscillation amplitude,
• a master oscillator supplying a master wave of fixed frequency and coupled to the control input of the current source of the analogue oscillator,
• the analogue oscillator and the master oscillator being tuned to the same frequency,
• the current source supplying, in the presence and in the absence of an object, an oscillating current of frequency equal to the frequency of the master wave and in phase with it, the current injected into the oscillating circuit remaining approximately constant when a magnetic object approaches and being an analogue function of the approach of a non-magnetic object.