An instrument used for the quantitative measurement of the proportion of a particular gas in a mixture. Different gases absorb infrared at different characteristic frequencies. In the analyser a beam of infrared of the frequency known to be absorbed by the gas under investigation is passed through the gas sample. The instrument also contains a plate sensitized to detect infrared of this frequency. The amount of infrared detected by the plate will fall as the proportion of the gas in the sample increases. Infrared analysers are used for simple measurements, especially the continuous monitoring of air for a given pollutant. They are also used to measure rates of respiration or photosynthesis by recording changes in carbon dioxide level. More complicated analyses of gas mixtures can be made using a * spectrophotometer. |
