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 FIGURE 2-30
Using a Pitot Tube and Manometer to Measure
Velocity or Static Pressure
2.17 INCLINED MANOMETER. The manometers discussed up to this point have
been U-tube manometers. That is, in order to measure a static or velocity
pressure of 1.0 inches w.c., a vertical displacement of 1.0 inches in a tube
must be read. However, in reading commonly encountered velocity pressures
in air conditioning ducts, pressures of only a few hundredths of an inch
must be read. With a U-tube manometer, it is impossible to read hundredths
of an inch with any degree of accuracy. For accuracy, the inclined
manometer is used (Figure 2-31). It essentially spreads out the 1 inch of
vertical column into a much longer horizontal length. The actual vertical
rise is still 1 inch, but it becomes much easier to read accurately when the
scale has been expanded.
FIGURE 2-31
Inclined Manometer
2-29
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