An Analyzer for Gases, Vapours and Liquids

1,161,440. Photo-electric radiation absorption analyzer. SPETSIALNOE KONSTRUKTORSKOE BJURO ANALITICHESKOGO PRIBOROSTROENIA AKADEMII NAUK SSSR. Dec.8, 1967, No.55873/67. Heading G1A. In a radiation absorption analyzer where sample and reference beams of different wavelength ranges are alternately directed along the same radiation path through a sample under test on to a photoelectric detector, a variable compensator having different absorption coefficients for the sample and reference beams equalizes the detected intensity of the two beams thereby compensating for and providing an indication of the absorption of the sample beam by the sample. In Fig. 1 a rotating disc having different transmissive sections 7 and 8 alternately passes radiation of sample and reference wavelength ranges from a source 1 to a detector 3 through a test chamber 4. A sample gas or liquid flows through the chamber 4. An optical wedge 10 having different absorption coefficients for the sample and reference wavelength ranges is moved in or out of the beam in accordance with the detector output and the position, indicated at 21 and recorded at 22, indicates the absorption of the sample beam by the gas or liquid. The movable wedge 12, filter 15 and windows 5, 6 are made of similar material to that of wedge 10 and are used to set the zero of the analyzer. Wedges 11 and 13 are of neutral material and avoid the beams being deflected. In another arrangement Fig. 2 (not shown) the wedges 10, 11 and 12, 13 are replaced by adjustable bellows containing gas exhibiting a similar differential absorption.