Instrumentation Engineering Question:

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When an AC excitation signal is applied to the Primary Coil
(P), voltages are induced in the two Secondary Coils (S).
The MAGNETIC CORE inside the COIL WINDING ASSEMBLY provides
the magnetic flux path linking the Primary and secondary
Coils.Since the two voltages are of opposite polarity, the
Secondary Coils are connected series opposing in the
center, or Null Position. The output voltages are equal
and opposite in polarity and, therefore, the output voltage
is zero. The Null Position of an LVDT is extremely stable
and repeatable.
When the MAGNETIC CORE is displaced rom the Null
Position, an electromagnetic imbalance occurs. This
imbalance generates a differential AC output voltage
across the Secondary Coils which is linearly proportional
to the direction and magnitude of the displacement.
As shown in the figure, when the MAGNETIC CORE is moved
from the Null
Position, the induced voltage in the Secondary Coil, toward
which the Core is
moved, increases while the induced voltage in the opposite
Secondary Coil
decreases.
LVDTs possess the inherent ruggedness and durability of a
transformer and
truly provide infinite resolution in all types of
environments. As a result of the
superior reliability and accuracy of LVDTs, they are the
ideal choice for linear
motion control.