Abstract
This paper describes the operation of a direct reading polychromator that is being used to evaluate the concentrations of radiating species in HID lamps. The instrument differs from a monochromator in that many spectral regions of a dispersed light source can be detected simultaneously. By selecting narrow wavelength regions centered on known atomic transitions, the instrument can detect the real time light levels from a variety of radiating species in a light source. The authors discuss in detail the relationship between the observed light levels to the radiating species concentration and compare results obtained from the polychromator with results from a scanning monochromator.