TGA100A Trace Gas Analyzer Overview
OV6. Micrometeorological Applications
The TGA100A is ideally suited to measure fluxes of trace gases using
micrometeorological techniques. Its rugged design allows it to operate reliably
in the field with minimal protection from the environment, and it incorporates
several hardware and software features to facilitate these measurements.
OV6.1 Eddy Covariance
The TGA100A's frequency response, sensitivity, and selectivity are optimized
for measuring trace gas fluxes using the eddy covariance (EC) method. A
typical eddy covariance system (illustrated in Figure OV6.1-1) includes a
TGA100A, a CSAT3 sonic anemometer, and a datalogger.
GROUND
LUG
CS I/O
COMPUTER RS-232
(OPTICALLY ISOLATED)
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CONTROL I/O
CONTROL I/O POWER
UP
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Sample Pump
Sample Intake
CSAT3 Sonic
Anemometer
PD1000
Sample
Dryer
Datalogger
SDM
Cables
TGA100A
Analyzer
Reference
Gas
Dryer Purge Tubing
Sample
Tubing
FIGURE OV6.1-1. Example Eddy Covariance Flux 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 high flow
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 TGA100A analyzer is located near the base of the measurement
mast to minimize the length of sample tubing. This minimizes the attenuation
of high frequencies in the concentration data as the air sample flows through
the tube. The sample pump requires minimal shelter and can be located up to
90 m (300 ft) away from the analyzer, connected by 1” ID suction hose.
A Campbell Scientific datalogger collects synchronized data from the sonic
anemometer and the TGA100A through SDM interface cables. Analog outputs
are available for use with other data loggers. The datalogger records the raw
time series data as well as the results of an online EC flux calculation.
OV-8
(39 paginas)
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