Frequency Response of a New Closed-Path Trace Gas Analyzer for Eddy-Covariance Flux Measurements

English Abstract:

The TGA200A (Campbell Scientific, Inc.) is a new trace gas analyzer designed to measure nitrous oxide or methane mixing ratios, or carbon dioxide isotope ratios. It is similar to the earlier TGA200, but it uses a thermoelectrically cooled laser to avoid the need for cryogenic cooling. The TGA200A also uses a smaller sample cell to provide good frequency response for eddy covariance applications, even with a lower-power sample pump.

The frequency response of the TGA200A was measured by injecting an impulse of N2O at the inlet. This measured impulse response was then Fourier transformed and normalized to give the frequency response. This test was repeated at various flow rates that represent a range of pump capacities to demonstrate the tradeoff of frequency response vs. power required for the sample pump.