A design is presented for a double-beam infra-red analyzer that utilizes the chopped-light principle. The advantages of this instrument are low rate of drift at high sensitivities, freedom from the effects of ambient temperatures, and general ruggedness, all of which make the system adaptable to plant analytical and control problems. The receiving system consists of a thermistor bolometer and tuned amplifier. Performance data are given for the butadiene recycle impurity system of a GR-S synthetic rubber plant stream.
GILBERT KIVENSON, RALPH T. STEINBACK, and MYRTLE RIDER, "An Infra-Red Chopped-Radiation Analyzer," J. Opt. Soc. Am. 38, 1086-1089 (1948)