Campbell Wind Monitor Series, Product Manual, Page: 23 / 30

Appendix C. Wind direction
sensor orientation
C.1 Determining true north and sensor
orientation
Orientation of the wind direction sensor is done after the data logger has been programmed,
and the location of true north has been determined. True north is usually found by reading a
magnetic compass and applying the correction for magnetic declination; where magnetic
declination is the number of degrees between true north and magnetic north. The preferred
method to obtain the magnetic declination for a specific site is to use a computer service offered
by NOAA at
www.ngdc.noaa.gov/geomag . The magnetic declination can also be obtained from
a map or local airport. A general map showing magnetic declination for the contiguous United
States is shown in
FIGURE C-1 (p. 22).
Declination angles east of true north are considered negative, and are subtracted from 360
degrees to get true north as shown
FIGURE C-2 (p. 22) (0° and 360° are the same point on a
compass). For example, the declination for Logan, Utah is 11.78° East (11 August 2015). True north
is 360° – 11.78°, or 348.22° as read on a compass. Declination angles west of true north are
considered positive, and are added to 0 degrees to get true north as shown in
FIGURE C-3 (p. 23).
Orientation is most easily done with two people, one to aim and adjust the sensor, while the
other observes the wind direction displayed by the data logger.
1. Establish a reference point on the horizon for true north.
2. Sighting down the instrument center line, aim the nose cone, or counterweight at true
north. Display the input location or variable for wind direction by using a laptop or
keyboard display.
3. Loosen the U-bolt on the CM220 or the set screws on the Nu-Rail that secure the base of
the sensor to the crossarm. While holding the vane position, slowly rotate the sensor base
until the data logger indicates 0 degrees. Tighten the set screws.
Wind Monitor Series 21