Section 2. Assembly of Components and Erection of Tower
2-5
Figure 2-4 Sighting Along the Tower to Check the Magnetic Bearing
3.
Sight along the tower, from the mast end towards the base as shown in
Figure 2-4, above and, using a high quality compass, establish its magnetic
bearing. It is recommended that you set up the wind sensor with respect to
true
north. Using an ordnance survey map (or other documentation) establish the
declination angle for true north in your vicinity. Calculate true north by adding
this angle to the magnetic bearing. For example, if the magnetic bearing is +37
degrees and the declination angle is +3 degrees, the adjusted bearing for true
north is 37+3=40 degrees. (See Appendix A for a general discussion about true
north and declination angles.) Make a note of this adjusted angle as you will
need to use it to accurately set your wind direction sensor.
4.
Attach the wind sensor mounting arm to the tower mast assembly and line it up
in an approximately east/west direction (not in line with the pyranometer).
5.
Once the wind sensors are mounted, you may need to rotate the body to ensure
correct wind direction readings and/or to move the cable to a convenient
position. A pair of spacers and long screws are included with the 011E arm to
allow this. In addition, a nylon washer is supplied which can be used to stop the
spacer and screw falling out of the mounting arm during installation.
6.
Weight the fin of the wind sensor, by attaching a weight of some kind, so that it is
held perpendicular to the ground. A makeshift weight might be a heavy bolt
attached to the fin by two strips of adhesive insulating tape – see Figure 2-5.
7.
Connect the windvane (temporarily) to the datalogger (see the datalogger
and/or windvane manuals for details), and, if using a CR10/10X attach the
CR10KD keyboard/display (or computer running appropriate software) to the
datalogger. Use the *6 Mode on the datalogger to display the input location for
wind direction measurements.
8.
Whilst the windvane fin is held (by the weight) perpendicular to the ground,
loosen the body of the windvane and rotate it until the display shows the angle
for true north (see paragraph 3 above). After ensuring the windvane is still
vertical, secure the body in this position. The windvane is now set to true north.
Remove the weight.
9.
Disconnect the sensor from the datalogger and secure the sensor wiring to the
tower with cable ties. Ensure that there is sufficient wiring to reach the position
of the datalogger enclosure when the tower is fully raised to its working
position.
Ensure tower is lying horizontally along the ground
Sight along tower from top to base to
establish the magnetic bearing
