Multi-wavelength based ozone measurement method and apparatus

Abstract

Systems and methods for providing an ultra-stable measurement of the density of a fluid/gas species such as ozone in a mixture. The technique is based on information extracted from multi-wavelength light absorption, at which the species exhibits different absorption properties (coefficient values). The technique provides real-time compensation for short- and long-term instability in the light source and detector, and for detectable changes in the optical characteristics of the cell, thus improving the accuracy of the measurement while making frequent zeroing of the instrument unnecessary. In addition, the invention provides a high-performance technique for measuring ultra-high ozone densities using absorption at the Chappuis band. The invention provides in an embodiment a system and method for detection of a gas component such as ozone in a gas mixture utilizing a light source providing light output in the visible spectrum corresponding to maximum and minimum absorption wavelengths for the gas component of interest. A process gas containing ozone or other gas component to be measured is supplied to a cell or cuvette having an optical input end and an optical output end. The light sources are desirably coupled to a first ('sample') optical path which provides light from the sources to the optical input end of the cell, and to a second ('reference') optical path which does not pass through the sample gas. A sensor apparatus is disposed to receive the light transmitted through the cell, and through the second optical path. The second optical path serves as a reference path, while the first optical path serves as a measurement path. The sensor apparatus provides electrical outputs representative of the intensity of light impinging thereon, the outputs being provided to a processor operative to calculate the concentration of the ozone or other gas component of interest in the gas cell.