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Instrumentation and Control Volume 1 of 2 | Next
Figure 4 Strain Gauge Pressure Transducer |
PRESSURE DETECTION CIRCUITRY
Pressure Detectors
PRESSURE DETECTION CIRCUITRY
Any of the pressure detectors previously discussed can be joined to an electrical
device to form a pressure transducer. Transducers can produce a change in
resistance, inductance, or capacitance.
EO 1.6
EXPLAIN how a strain gauge pressure
transducer produces an output signal including:
a.
Method of detection
b.
Method of signal generation
EO 1.7
Given a basic block diagram of a typical pressure
detection device, STATE the purpose of the following
blocks:
a.
Sensing element
b.
Transducer
c.
Pressure detection circuitry
d.
Pressure indication
Resistance-Type Transducers
Included in this category of transducers are strain gauges and moving contacts (slidewire variable
resistors). Figure 3 illustrates a simple strain gauge. A strain gauge measures the external force
(pressure) applied to a fine wire. The fine wire is usually arranged in the form of a grid. The
pressure change causes a resistance change due to the distortion of the wire. The value of the
pressure can be found by measuring the change in resistance of the wire grid. Equation 2-1
shows the pressure to resistance relationship.
(2-1)
R
KL
A
where
R = resistance of the wire grid in ohms
K = resistivity constant for the particular type of wire grid
L = length of wire grid
A = cross sectional area of wire grid
IC-02
Page 6
Rev. 0
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