Abstract: A non-dispersive infrared (NDIR) multi-gas analyzer has an optical element that is positioned with respect to the axis of incident IR radiation such that it passes nearly all of the IR energy within a narrow band pass to one detector and reflects nearly all of the IR energy outside the narrow band pass to another detector. Thus, the optical element simultaneously functions both as a narrow band pass filter and a beam splitter, which transmits nearly all the IR energy within a band pass and reflects nearly all the IR energy outside the band pass. Additionally, the separation of the incoming energy can be achieved without an extended roll off. This allows using a reference transmission band that is very close to the absorption band of the gases of interest. It more specifically allows using a reference transmission band that is located between the absorption bands for hydrocarbons and carbon dioxide in an infrared analyzer that uses beam splitters.

Abstract: An improved gas analyzer for measuring the presence of one or more gaseous compounds in a gas sample. The gas analyzer has an infrared source stablized against temperature variations by a radiation loading scheme in combination with a selected source environmental temperature sensitivity to provide a stable source temperature without a conventional temperature controller. A rotating interference filter assembly is disposed in the optical path. This assembly alternately totally blocks radiation, passes radiation in a wave length band which will not be absorbed by a random gas sample, and sequentially passes radiation in one or more additional bands which will be absorbed by one or more gases in the sample cell. The sample cell features a unique enclosed cell with infrared transparent windows which are substantially free of impingement of contaminants of the gas sample thereon. A unique detector provides protection against deterioration from moisture while allowing easy and inexpensive assembly.

Abstract: An improved gas analyzer for measuring the presence of one or more gaseous compounds in a gas sample. The gas analyzer has an infrared source stabilized against temperature variations by a radiation loading scheme in combination with a selected source environmental temperature sensitivity to provide a stable source temperature without a conventional temperature controller. A rotating interference filter assembly is disposed in the optical path. This assembly alternately totally blocks radiation, passes radiation in a wave length band which will not be absorbed by a random gas sample, and sequentially passes radiation in one or more additional bands which will be absorbed by one or more gases in the sample cell. The sample cell features a unique enclosed cell with infrared transparent windows which are substantially free of impingement of contaminants of the gas sample thereon. A unique detector provides protection against deterioration from moisture while allowing easy and inexpensive assembly.