A non-dispersive analyzer takes advantage of a molecular signature without using a dispersive element such as a prism, grating or interferometer. Instead, the radiation sources and detectors are matched to the spectra of the absorbing compounds either by their inherent response characteristics or by the use of filters. Laser sources may be tuned to the absorption lines of the compound being measured, or narrow-band interference filters may be used. Also, spectrum matching through the use of gas filters has found wide application.

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