A CSAT3 sonic anemometer (Campbell Scientific, Inc., Logan, UT) can be configured to log raw flux data in conjunction with an LI-7500A or LI-7200 infrared gas analyzer from LI-COR in a compressed .ghg file format. The .ghg file format makes it possible to continuously collect raw flux data for more than two months on a single 4 GB USB drive and to process data conveniently with LI-COR’s new EddyPro™ Express flux data processing software.
1. The CSAT3 is connected to an LI-7550 Analyzer Interface Unit through analog output/input channels. There are three cabling options for interfacing the CSAT3 to the LI-7550:
a) The LI-7550 to CSAT3 interface cable (p/n 9975-035) provides a direct cable connection (shown below). This cable is not included with the LI-7500A/LI-7200 but can be ordered separately.
b) The CSAT3 analog output cable can be wired into the LI-7550 auxiliary sensor interface box (LI-COR p/n 7550-101).
c) The LI-7550 analog input/output cable (p/n 392-10109) can be spliced into the CSAT3 analog output cable, or soldered into the CSAT3’s analog connector.
2. Analog outputs from the CSAT3 are turned off by factory default. To turn them on, use the CSAT32 software, which can be downloaded for free from http://www.campbellsci.com/19_1_9999_68. Set the Measurement Rate of the CSAT3 to 60 Hz for better data synchronization with the outputs from the gas analyzers, and choose an Analog Out range (Low for ±32.768 m s-1, High for ±65.536 m s-1) appropriate for your measurement conditions.
3. Follow the quick start guide, which can be downloaded at ftp://ftp.licor.com/perm/env/LI-7200/GHG_Quick_Start_Guide_print.pdf, to set up LI-COR gas analyzers to log eddy covariance data in the .ghg file format. The CSAT3 provides the analog outputs as U, V, W, and Speed of Sound (SOS). The LI-7550 will need to be configured to read SOS, rather than sonic temperature (Ts), for a CSAT3.