Abstract: A sensing apparatus and method for use in the optical absorption analysis of the NO2 content of a gas sample. The apparatus and method employ radiation from a semiconductor radiation source. The emission spectrum of the radiation has a maximum wavelength of about 600 nm, preferably 380-520 nm. The radiation is passed through the gas sample and sensed by a detector to provide an output signal indicative of the NO2 content of the gas sample. A pair of alternately energized radiation sources may also be used. The sensor apparatus and method may be employed in conjunction with other gas sensing apparatus and methods, such as IR CO2 measurement or NO sensing.

Abstract: A radiation source assembly and transducer incorporating same are suitable for use in measuring spectral absorption properties of a substance to be analyzed, such as a gas. The radiation source assembly has an optical axis. A measuring radiation source provides radiation in the direction of the axis and a reference radiation source provides radiation in the direction of the axis. An optical diffuser is spaced from the radiation sources along the axis. Radiation from the measuring radiation source and radiation from the reference radiation source are applied to the diffuser and the diffuser forms an exiting radiation beam for the assembly from the radiation of the measuring radiation source and reference radiation source. The exiting radiation beam extends along the axis.