20
2.5.222 Static instruments
These types of instruments depend on the hydrodynamlc
principles of the dynamic and static pressure in streaming
gases and liquids.
- The "Pitot tube, exposed in front of the airflow
indicates the dynamic pressure, while a tube exposed
parallel to the airflow shows the static pressure. If the
pressure difference and the specific mass of the air are
known, the windspeed can be deduced.
- With the "Venturi Tube, pressure measurements are taken at
places having different cross sections. In the narrow
section of the tube the airflow is accelerated, thus
creating a lower pressure compared with the one in the
wider section. Using a differential manometer, the
instantaneous windspeed can be measured.
Both the Pitot tube and the Venturi tube must be placed
parallel to the airflow.
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