Delta OHM DO2003, Manual

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AP473 S1 … AP473 S4
P
ITOT
T
UBE
P
ROBES FOR THE
M
EASUREMENT OF
A
IR
S
PEED
E
QUIPPED WITH
SICRAM M
ODULE
The Pitot tube is an easy method to measure air speed in hard-to-reach positions, such as air ducts,
and in applications where air speed and temperature are very high. As no air passes through it, the
Pitot tube is particularly suitable for measurements in hostile environments.
M
EASURING
P
RINCIPLE
Static Pressure Holes Total Pressure Hole
STATIC PRESSURE
SPEED PRESSURE
TOTAL PRESSURE
The pressure inside the duct is the result of three different pressures:
1) atmospheric pressure (barometric B)
2) static pressure Ps
3) dynamic pressure Pv due to the non-null speed of the air inside the duct.
The following formula provides the air speed: as you can see, it depends on the three pressures and
on air temperature.
(1)
⎥⎦
⎤
⎢⎣
⎡
⋅
+
⋅ ⋅ ⋅ =
Pv
Ps 100.000
100.000
289
T
B
1000
1.291 v
K [T]
Pa [Ps] [Pv]
mbar [B]
m/s [v]
° =
= =
=
=
The Pitot tube provides the difference between the pressure available on the front mouth and the
one measured through the lateral holes, that is Pv dynamic pressure:
(Ps+Pv) – Ps = Pv