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FIGURE 2.42 Classification and Types of Sensors 65
Operating principle
of inductive
proximity sensor.
The oscillator circuit generates a radio-frequency electromagnetic
field that radiates from the ferrite core and coil assembly. The field is
centered around the axis of the ferrite core, which shapes the field
and directs it at the sensor face. When a metal target approaches and
enters the field, eddy currents are induced into the surfaces of the
target. This results in a loading effect, or “damping,” that causes a
reduction in amplitude of the oscillator signal (Fig. 2.43).
FIGURE 2.43 Induced eddy current.
