Fluke Pitot Tube (PT12)

12 inch Pitot Tube for use with the Fluke 922

Pitot tubes are commonly used to measure velocity
pressure within a duct. Velocity pressure is the
pressure resulting from moving air within a duct. As
air velocity increases, velocity pressure increases
accordingly. A Pitot tube is used to sense both total
pressure (TP) and static pressure (SP), which are used
to calculate velocity pressure (VP) according to the
following equation:
VP = TP-SP
Because airflow through a duct is turbulent and of
varying velocities, a single reading does not represent
the overall air velocity in the duct. Several readings
must be taken across a traverse plane, converted to
velocity, and then averaged. To take an accurate air
velocity measurement, the Log-Tchebycheff rule
provides the greatest uniformity because it accounts
for the friction effect of air moving near duct walls.
Figures 1 and 2 show the points along the traverse
plane where measurements should be taken, either in
rectangular or circular ducts.