| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve the detecting sensitivity by providing a luminous flux branching means, a luminous flux transmitting shielding means, first detector arranged on one infrared transmitting window of first and second measuring cells, and a second detector arranged on the other infrared transmitting window of third and fourth measuring cells. SOLUTION: The advancing directions of a first infrared luminous flux (3A, 3B) transmitted by a first measuring cell 3 and a second infrared luminous flux (4A, 4B) transmitted by a second measuring cell 4 are set to mutually opposed directions, for example, the directions shown by the actual lines (3A, 4B) or dotted line (3B, 4B). Consequently, the signals detected by first and second detectors 5, 6 can be detected as ac signals by alternately reversing the advancing directions of the infrared luminous fluxes (3A, 4B) (3B, 4A) advancing in the measuring cells 3, 4, so that a low concentration gas component can be detected with high sensitivity, and the influence of zero point drift can be removed.</p> |
