DPM TT 570 D Betriebshandbuch - Seite 14
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Page 12
Principle of Operation:
Pitot Head
Velocity Pressure* = Total Pressure – Static Pressure
*
Calculated by the Micromanometer
Log Linear Rule for Traverse Points on 3 Diameters in a
Circular Duct:
Alternative Measuring Points and Traverse Lines
Relative to Side Lengths for Regular Ducts:
DUCT TRAVERSE POINTS
SP
0.032D
0.135D
0.321D
0.679D
0.865D
0.968D
D
0.939D
0.765D
0.563D
0.437D
0.235D
0.061D
The nose of the Pitot Tube should face
directly into the airstream thus the Total
Pressure flows down the inner tube which
TP
is connected to the Signal In port.
The static holes are positioned around the
side of the Pitot Tube and lead into an
outer tube. This is connected to the black
tubing which in turn is connected to the
Reference port.
Ideally traverse points should be at least six
duct diameters away from any bend or
obstruction in the system.
The Pitot Tube should be inserted at right
angles to the walls of the ducts and
measurements are taken in the positions
shown in the diagrams (left).
The directional pointer can be used to
ensure that the Pitot Tube head is parallel
to the duct walls.