Page 104 - Fluid Power Engineering

82 Chapter Six

α< 4,α > 356 to α = 0; (ii) if accurate direction readings are desired
around zero degrees, then the wind vane may be installed with an
offset. In the second case, if the most frequent wind direction is north
and the least frequent wind direction is east, then the vane may be
oriented in the east direction with appropriate compensation in the
data logger. Figure 6-1c is a picture of a wind vane.

Placement of Sensors
A met-tower has several instruments mounted on it at different
heights. A frequently used configuration of met-tower is:

60 m monopole tower

two anemometers at 60 m

one wind vane at about 56 to 58 m

two anemometers at 40 m

two anemometers at 30 m

one wind vane at about 26 to 28 m

Temperature sensor at 3 m

If present, barometric pressure and relative humidity sensors

are placed at 3-m level
Datalogger and communication device in an enclosed box at

3-m level
All the instruments are mounted on booms of length 60 to 95 in.
to minimize the impact of tower in the flow. Figure 6-5 illustrates
the orientation of two anemometers and wind vane at the top of the
tower.

FIGURE 6-5 Mono-
pole tower with two
anemometers and
one wind vane.