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Figure 5 Strain Gauge Used in a Bridge Circuit | Up
Instrumentation and Control Volume 1 of 2 | Next
Figure 8 Differential Transformer |
Pressure Detectors
PRESSURE DETECTION CIRCUITRY
Other resistance-type transducers combine a bellows or a bourdon tube with a variable resistor,
as shown in Figure 6. As pressure changes, the bellows will either expand or contract. This
expansion and contraction causes the attached slider to move along the slidewire, increasing or
decreasing the resistance, and thereby indicating an increase or decrease in pressure.
Figure 6 Bellows Resistance Transducer
Inductance-Type Transducers
Figure 7 Inductance-Type Pressure Transducer Coil
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 7. As the core moves within
the coils, the inductance of one coil will
increase, while the other will decrease.
Rev. 0
Page 9
IC-02
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