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Optical Engineering

Measurement of methane gas concentration by detecting absorption at 1300 nm using a laser diode wavelength-sweep technique
Author(s): Kazutoshi Noda; Masanori Takahashi; Ryoji Ohba; Seiichi Kakuma
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Paper 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.

Paper Details

Date Published: 1 January 2005
PDF: 6 pages
Opt. Eng. 44(1) 014301 doi: 10.1117/1.1829095
Published in: Optical Engineering Volume 44, Issue 1
Show Author Affiliations
Kazutoshi Noda, National Institute of Advanced Industrial Science (Japan)
Masanori Takahashi, Hokkaido Univ. (Japan)
Ryoji Ohba, Hokkaido Univ. (Japan)
Seiichi Kakuma, Hokkaido Univ. (Japan)

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