Campbell Scientific TGA100 Trace Gas Analyzer Manual - Manual (Page 17)

1.6 Micrometeorological Applications
The TGA100 is ideally suited to measure fluxes of trace gases using micrometeorological techniques. In addition to its
rugged design that allows it to operate reliably in the field with minimal protection from the environment, it also
incorporates several hardware and software features to facilitate these measurements.
1.6.1 Eddy Covariance
The TGA100's sample rate, frequency response, sensitivity and selectivity are optimized for measuring trace gas fluxes
using the eddy covariance (EC) method. It is designed to collect three-dimensional wind data from a CSAT3 sonic
anemometer while synchronously measuring trace gas concentration. Figure 1-5 illustrates a typical EC application.
The sonic anemometer and air sample intake are mounted on the measurement mast. Tubing connects the air sample
intake to the inlet of a PD1000 sample air dryer, which filters and dries the air sample. A needle valve at the outlet of
the PD1000 sets the sample flow rate, typically to approximately 15 slpm. The TGA100 analyzer is located near the
base of the measurement mast to minimize the length of sample tubing. This avoids the attenuation of high frequencies
in the concentration data that can be caused by excessive tubing length. The TGA100 PC requires shelter from the
environment, but can be located up to 500 m (1650 ft) away from the TGA100 analyzer, connected by fiber optic cable.
The sample pump requires minimal shelter and can be located up to 90 m (300 ft) away from the analyzer, connected
by the suction hose. The CSAT3 connects to the TGA analyzer by way of a TL925 serial interface module, which can
be mounted inside the analyzer enclosure for protection from the environment.
CSAT3 Cable
Figure 1-5. Example Eddy Covariance Flux Application
17