This analyzer can be configured to measure at any wavelength within the ultraviolet or visible portions of the electromagnetic energyspectrum. Since numerous gases and liquids have a useful absorbance peak in the ultraviolet region, a wide variety of applications are possible. The analyzers optical path (figure 1) consists of a UV source, sample cell, and detector. A filter wheel located in front of the detector continuously rotates a reference and measuring filter in and out of the optical path. The material of interest continuously flows through the sample cell where the optical energy is absorbed at the various wavelengths in accordance with its composition. The analyzer utilizes the reference wavelength to compensate for extraneous phenomena (turbidity, dirt on optics, source drift, etc.) thereby producing a high degree of stability over long periods.