Inductive Proximity Sensors


   Inductive proximity sensors operate under the electrical principle of inductance. Inductance is the phenomenon where a fluctuating current, which by definition has a magnetic component, induces an electromotive force (emf) in a target object. To amplify a deviceís inductance effect, a sensor manufacturer twists wire into a tight coil and runs a current through it.
   An inductive proximity sensor has four components; The coil, oscillator, detection circuit and output circuit. The oscillator generates a fluctuating magnetic field the shape of a doughnut around the winding of the coil that locates in the deviceís sensing face.
   When a metal object moves into the inductive proximity sensorís field of detection, Eddy circuits build up in the metallic object, magnetically push back, and finally reduce the Inductive sensorís own oscillation field. The sensorís detection circuit monitors the oscillatorís strength and triggers an output from the output circuitry when the oscillator becomes reduced to a sufficient level.




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