Vaisala WXT520 - Manual (Page 43)

Chapter 4 _______________________________________________________________ Installation
VAISALA_______________________________________________________________________ 41
Aligning WXT520
To help the alignment, there is an arrow and the text "North" on the
bottom of the transmitter. WXT520 should be aligned in such a way that
this arrow points to the north.
Wind direction can be referred either to true north, which uses the
earth’s geographic meridians, or to the magnetic north, which is read
with a magnetic compass. The magnetic declination is the difference in
degrees between the true north and magnetic north. The source for the
magnetic declination should be current as the declination changes over
time.
0003-011 Figure 18 Sketch of Magnetic Declination
Compass Alignment
To align the WXT520, proceed as follows:
1. If WXT520 is already mounted, loosen the fixing screw on the
bottom of the transmitter so that you can rotate the device.
2. Use a compass to determine that the transducer heads of WXT520
are exactly in line with the compass and that the arrow on the
bottom of WXT520 points to the north.
3. Tighten the fixing screw on the bottom of the transmitter when the
bottom arrow is exactly aligned to north.