Abstract: One embodiment of the present invention is an analyzer of a multiplicity of gases in a sample gas that includes: (a) an infrared source of infrared radiation; (b) a multiplicity of band-pass filters, including a reference band-pass filter, and an opaque area; (c) a movement mechanism that places the band-pass filters and the opaque area in front of the infrared radiation at predetermined times, and includes a location pickup mechanism; (d) a location pickup mechanism detector that generates movement mechanism timer signals; (e) a sample cell disposed in a path of the infrared radiation through which the sample gas travels; (f) a gas temperature sensor and a pressure transducer that generate temperature and a pressure signals; (g) a detector that detects infrared radiation that has passed through the sample cell and generates detector signals; and (h) a controller that analyzes the movement mechanism timer signals, the detector signals, the temperature signal, and the pressure signal to provide concentrations

Abstract: A mixture of H.sub.2 O, CO.sub.2 and CO are measured in the same sample chamber by infrared radiation passing through the chamber and absorption filters passing a narrow band in their respective absorption curves to an infrared detector. Background radiation is zeroed by grounding the detector response when an opaque segment is disposed in the path. A reference filter detects drift which is automatically corrected.

Abstract: A beam of infrared radiation encompassing the absorption band of the hydrocarbon alkanes is passed through an unconfined sample of test gas after which the beam is chopped before it impinges upon an interference filter. The filter restricts radiation passing therethrough to the spectral interval corresponding to the absorption band of the hydrocarbon alkanes. The filtered radiation impinges on an infrared detector which produces a signal that on being amplified, detected and demodulated is an analog signal of magnitude functionally related to the product of concentration and carbon number of the n-alkanes (flammability index) of a mixture of hydrocarbons irrespective of their individual carbon numbers. The apparatus is unitarily arranged in an elongated rod-like housing adapted for convenient hand-held use.

Abstract: A reflector or mirror for the visible and rear infrared spectrum is formed by multicoating copper with one-fifth wavelength and three-quarter wavelength films. These films are alternating low and high index films, and MgF.sub.2 and TiO.sub.2 are presently preferred. A thin bonding layer of TiO.sub.2 is used to secure adhesion of the MgF.sub.2 to the copper. This coating enhances the reflectance in the visible range without appreciable degradation of reflectance in the near infrared, so that the resultant curve of reflectance-versus-frequency is substantially flat. The resulting coating is hard and tough and may be cleaned without injury and withstands high humidity.

Abstract: A multiple gas analyzer is disclosed utilizing the infrared absorption principle for determining the quantity of two or more gases with a sample tube and a reference tube in parallel orientation with an infrared source between one end of the two tubes, and an infrared detector assembly between the other end of the tubes. Immediately opposed to each end of the tubes are a pair of mirrors, one being a transmitting mirror remote from the infrared source and directing the infrared beam in parallel paths through the reference tube and sample tube, and a receiving mirror opposite the infrared detector assembly to focus the infrared beam after passing through the tubes on to the infrared detectors.