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[Instrumentation Table of Contents]
[Sensors and Transducers Suppiers Menu]
The inductance-type transducer consists of
three parts: a coil, a movable magnetic core, and a pressure
sensing element. The element is attached to the core, and, as
pressure varies, the element causes the core to move inside
the coil. An AC voltage is applied to the coil, and, as the
core moves, the inductance of the coil changes. The current
through the coil will increase as the inductance decreases.
For increased sensitivity, the coil can be separated into two
coils by utilizing a center tap, as shown in Figure A-1. As
the core moves within the coils, the inductance of one coil
will increase, while the other will decrease.
Figure A-1
Another type of inductance transducer,
illustrated in Figure A-2, utilizes two coils wound on a
single tube and is commonly referred to as a Differential
Transformer.
Figure A-2
The primary coil is wound around the center
of the tube. The secondary coil is divided with one half
wound around each end of the tube. Each end is wound in the
opposite direction, which causes the voltages induced to
oppose one another. A core, positioned by a pressure element,
is movable within the tube. When the core is in the lower
position, the lower half of the secondary coil provides the
output. When the core is in the upper position, the upper
half of the secondary coil provides the output. The magnitude
and direction of the output depends on the amount the core is
displaced from its center position. When the core is in the
mid-position, there is no secondary output.
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