Campbell Scientific 03001-L R.M. Young Wind Sentry Set - Manual (Page 19)

Appendix A. Wind Direction Sensor
Orientation
A.1 Determining True North and Sensor Orientation
Orientation of the wind direction sensor is done after the datalogger 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. Magnetic declination for a specific site
can be obtained from a USGS map, local airport, or through a computer service
offered by the USGS at www.ngdc.noaa.gov/seg/geomag/. A general map
showing magnetic declination for the contiguous United States is shown in Figure
A-1.
Declination angles east of True North are considered negative, and are subtracted
from 0 degrees to get True North as shown Figure A-2. Declination angles west
of True North are considered positive, and are added to 0 degrees to get True
North as shown in Figure A-3. For example, the declination for Logan, Utah is
14
° East. True North is 360° - 14°, or 346° as read on a compass.
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
datalogger.
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 using a hand-held keyboard display, PC, or palm.
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 datalogger indicates 0 degrees.
Tighten the set screws.
A-1