Measurement of methane gas concentration by detecting absorption at 1300 nm using a laser diode wavelength-sweep technique

Kazutoshi Noda; Masanori Takahashi; Ryoji Ohba; Seiichi Kakuma

doi:10.1117/1.1829095

1 January 2005 Measurement of methane gas concentration by detecting absorption at 1300 nm using a laser diode wavelength-sweep technique

Kazutoshi Noda, Masanori Takahashi, Ryoji Ohba, Seiichi Kakuma

Author Affiliations +

Optical Engineering, Vol. 44, Issue 1, 014301 (January 2005). https://doi.org/10.1117/1.1829095

Abstract

We develop a simple piece of equipment for measuring methane (CH₄) gas concentration based on IR absorption by sweeping the wavelength of light emitted from a laser diode (LD). The principle of IR absorption enables the selective measurement of CH₄ gas by detecting an absorption line that appears around 1300 nm in the specific absorption spectrum of CH₄. Our method is simpler and more user-friendly than existing measurement methods that involve a measurement system equipped with a cell filled with a known concentration of CH4 gas and a lock-in amplifier. The results of measurements using 220- and 660-mm measurement cells show that CH₄ gas concentration is proportional to absorbance within a concentration range of 5 to 90 vol %. It is also found that our measurement system can selectively measure only the concentration of CH₄ in city gas, which is composed of a mixture of flammable gases. Moreover, a simple technique for removing humidity using silica gel and calcium chloride reduces the influence of relative humidity. These results represent performance superior to other CH₄ measurement methods currently in use.

©(2005) Society of Photo-Optical Instrumentation Engineers (SPIE)

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Kazutoshi Noda, Masanori Takahashi, Ryoji Ohba, and Seiichi Kakuma "Measurement of methane gas concentration by detecting absorption at 1300 nm using a laser diode wavelength-sweep technique," Optical Engineering 44(1), 014301 (1 January 2005). https://doi.org/10.1117/1.1829095

Published: 1 January 2005

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