Campbell IRGASON, Руководство по эксплуатации продукта

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10.1 Data collection and processing with
EasyFlux DL
The EasyFlux DL is an open source CRBasic program that allows a CR6 or CR3000 data logger to
collect fully corrected measurements from an IRGASON instrument. The program is compatible
with other GPS and energy balance sensors which, in combination, can report corrected fluxes for
CO
2
, latent heat (H
2
O), sensible heat, ground surface heat flux, and momentum. The program
processes the EC data using commonly used corrections in the scientific literature. For detailed
information about downloading, installing, and configuring the free program, refer to the
EasyFlux DL manual located at www.campbellsci.com/easyflux-dl .
Of particular note is the manner in which EasyFlux DL processes information from the sonic
anemometer and is useful to understand when considering how to situate the analyzer and
anemometer at a given site.
EasyFlux DL reports the wind direction in both the sonic coordinate system (a right-handed
coordinate system, FIGURE 10-1 (p. 44)) and in the compass coordinate system (a left-handed
coordinate system, FIGURE 10-2 (p. 45)). To report the wind direction in the compass coordinate
system, the orientation of the sonic must be known. The sonic coordinate system is relative to the
sonic itself and does not depend on the sonic’s orientation. The compass coordinate system is
fixed to Earth. For the
EasyFlux DL program to compute the correct compass wind direction, the
azimuth of the sonic negative x-axis must be entered into the program. The output value for the
compass coordinate system is WD and the output value for the sonic coordinate system is WD_
Sonic. The program default value for the variable sonic_azimuth is 0. To report a true compass
wind direction, an appropriate value for sonic_azimuth must be entered into the program. The
default is appropriate only if the sonic is mounted such that the negative x-axis points to the
north.
NOTE:
Remember to account for magnetic declination at the installation site. See
Sonic anemometer
orientation (p. 61) for details.
The variable sonic_azimuth can be changed in LoggerNet or by using a CR100KD keypad. It can
be changed in LoggerNet by connecting the data logger to a computer, opening LoggerNet, and
going into the Public data table and changing the value in the sonic_azimuth field. Note that if
the units of the variables are being displayed in the field, the units must be deleted before
entering a value. If a new value is attempted to be sent along with the units in the field, then a
change will not be made. To change it on the keypad, go to the Site Var Settings menu, then go
to sonic_azimuth and enter a new value. Once a value is entered, the value is saved in the CPU.
IRGASON® Integrated CO
2
/H
2
O Open-Path Gas Analyzer and 3D Sonic Anemometer 43