LI-COR provides innovative solution for difficult ecosystem methane flux measurements

April 1, 2010 - Lincoln, Nebraska

The new LI-7700 Open Path Methane Analyzer from LI-COR Biosciences represents a significant step forward in atmospheric trace gas measurement instrumentation. Methane-producing ecosystems typically represent extreme environmental conditions for scientific instrumentation. Measuring ecosystem methane flux is difficult because methane analyzers designed as laboratory-based instrumentation have high power demands, require heavy pumps, and have overly restrictive operating temperature ranges. With more than 10 years of experience building open path trace gas analyzers, LI-COR designed the LI-7700 to be a rugged, easy-to-use instrument that is optimized for methane flux research and remote field deployment.

"We knew that the instrument needed to be capable of operating on a simple solar/battery power system, provide continuous data with little user-intervention and have high enough frequency response for eddy covariance measurements," says Bill Miller, LI-COR product manager. "It is important that the instrument have a low power requirement and be light enough for deployment in areas that lack easy access and transportation infrastructure." Power consumption for the LI-7700 is typically less than 10 watts and the instrument weighs 11.5 pounds.

"Long-term deployment capabilities are further enhanced by the unique self-cleaning lower mirror that decreases maintenance requirement and the frequency of site visits while providing more robust data sets," says Miller.

"The open path design of the LI-7700 provides elegant solutions to many of the challenges of measuring atmospheric CH4 flux over various ecosystems, while providing excellent co-spectra," adds Miller. "The instrument uses a single-mode tunable near infrared laser source, operating at ambient temperature, which greatly reduces power consumption and eliminates the need for cryogenic cooling systems."

The LI-7700 uses Wavelength Modulation Spectroscopy (WMS), which offers distinct advantages over other spectroscopic techniques used for trace gas measurements. The WMS technique provides a strong methane signal with very low noise. As a result, the instrument can use a shorter optical path-length with fewer reflections, reducing sensitivity to contamination of mirrors. LI-COR has an exclusive license agreement with Southwest Sciences to aspects of the WMS technology for LI-COR markets.

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