| 摘要 |
A method and apparatus for measuring the methane concentration in a gas, which comprises transmitting light having at least one wavelength band selected from a band of 1.6 mu m and a band of 1.3 mu m through an optical fiber having a small transmission loss in said wavelength bands to a measuring cell where an ambient gas comes in and out, absorbing the light in at least one characteristic absorption wavelength of methane gas, selected from a wavelength of 1.666 mu m and a wavelength of 1.331 mu m, in said measuring cell, transmitting the light through an optical fiber having a small transmission loss in at least one wavelength band selected from a band of 1.6 mu m and a band of 1.3 mu m to a band-pass filter, separating the light into at least one light having the methane gas absorption wavelength, that is, the wavelength to be measured, and at least one light having other reference wavelength, determining the intensity ratio of the light having the wavelength to be measured to the light having the reference wavelength, and calculating the methane gas concentration in the measuring cell from the so-determined intensity ratio.
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