Abstract: An infrared gas analyzer for measuring at least one component gas of a sample gas mixture. A beam of infrared radiation is periodically interrupted and propagated through a measuring cell through which the sample gas mixture flows. The infrared radiation beam is divided into a reference ray which is propagated through the measuring cell, and a selectivity cell which contains the component gas to be measured; and a measuring ray which is propagated through the measuring cell, and a gas-filled compensation cell. In one embodiment, the compensation cell and the measuring cell are serially coupled to one another so that the sample gas mixture flows through both. Alternatively, the compensation and measuring cells may be connected in parallel with respect to one another. Selective detectors are provided for producing an output signal responsive to the difference between the attenuation of the measuring ray and the attenuation of the reference ray, as they are propagated through their respective paths.

Abstract: Infrared absorption gas analyzer systems are provided with cells containing sulfur hexafluoride SF.sub.6 for determining the water vapor content of the gas to be measured. In another embodiment, sulfur hexafluoride is used as a selective filter for removing spectral components from a beam of infrared energy so as to prevent cross sensitivity which interferes with the measurement of other gas components. Electrical signals proportional to the water vapor content may be produced by measuring the increase in gas pressure as infrared energy is absorbed, by use of a diaphragm capacitors. In another embodiment, temperature responsive resistors measure the relative attenuation of the infrared energy as it propagates through respective gas components.