SPECTROSCOPIC ANALYSIS METHOD AND APPARATUS OF GAS

摘要

PROBLEM TO BE SOLVED: To enhance measuring accuracy by reducing fringe noise incapable of being cancelled by a method wherein a secondary differential absorption spectrum obtained in a cancel line containing no gas to be measured is substracted from that obtained in a measuring line containing gas to be measured. SOLUTION: In a method for measuring the concn. of a component to be measured in gas to be measured by transmitting semiconductor laser beam modulated in frequency through the gas to be measured to measure a secondary differential spectrum of light absorbing intensity, refined gas to be measured from which a component to be measured is removed is introduced into a sample cell 4, and laser beam from a semiconductor laser 1 is transmitted through this gas to obtain a background spectrum. The gas to be measured is introduced into the sample cell 4 and laser beam is transmitted through this gas to obtain a secondary differential spectrum. A corrected secondary differential spectrum obtained by subtracting the background spectrum from the secondary differential spectrum is used to measure the component to be measured.