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stage. 6 Oscillator (1) Switching status display (4) Internal constant voltage supply (7) Demodulator (2) Output stage with protective circuit (5) Active zone (coil) (8) Triggering stage (3) External voltage (6) Sensor output (9) Fig. 4.1.1: Block circuit diagram of an inductive proximity sensor The magnetic field which is directed towards the outside, is generated via a halfopen ferrite core shell of an oscillator coil and additional screening. This creates a
limited area across the active surface of the inductive proximity sensor, which is
known as the active switching zone.
When a voltage is applied to the sensor, the oscillator starts and a defined quiescent
current flows. If an electrically conductive object is introduced into the active
switching zone, eddy currents are created, which draw energy from the oscillator.
Oscillation is attenuated and this leads to a change in current consumption of the
proximity sensor. The two statuses – oscillation attenuated or oscillation
unattenuated – are electronically evaluated. © Festo Didactic GmbH & Co. KG • FP 1110 49 4. Inductive proximity sensors 1
4 a) 5 b)
Actuating element (1) R...
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- Spring '12