An inductive proximity sensor operates with a low

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Unformatted text preview: = 1 V/A. 11.1.1 Inductive proximity sensors Let us now consider the LC resonant circuit as applied in an inductive proximity sensor. The coil of an LC oscillator is inside a unilaterally magnetic half shell core. This oscillator oscillates typically at a frequency in the range of approx. 100 – 1000 kHz. The LC oscillator generates a high frequency electromagnetic alternating field (HF field), which is emitted on the active surface of the proximity sensor. The amplitude of oscillation decreases as a metallic conductor approaches the half shell core or oscillation stops completely. Eddy currents The cause is the withdrawal of energy as a result of a loss in eddy currents as the object approaches. If a piece of metal in a constant magnetic field is moved, this induces eddy currents in this piece of metal. The same happens if stationary metal parts are exposed to magnetically alternating fields. An inductive proximity sensor operates with a low power consumption of several microwatts and this has several advantages: • No significant magnetising effect • The HF field does not cause any interference • No temperature rise in the object to...
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