GB1078976A - Radiation analyser - Google Patents

Abstract

1,078,976. Photo-electric light absorption measurement. DISTILLERS CO. Ltd. April 15, 1965 [April 25, 1964], No. 17262/64. Heading G1A. In a radiation fluid analyzer of the kind described in Specification No. 899, 973 for determining the concentration of water in acetone by the absorption of infrared radiation in an overtone wavelength absorption band where chopped reference and sample beams are passed alternately by means of a cylindrical chopper through reference and sample cells of acetone and acetone and water and the resulting amplified D.C. signals passed by means of a switch to respective channels of a two-channel D.C. ratio measuring device, the switch is a transistor switch having a neutral position and driven into one of one two switching states by one of two photo-diodes placed in the path of the corresponding chopped beam. Alternatively, both chopped beams or the single beam before division and chopping into reference and sample beams may be passed through a single cell through which the water and acetone solution is flowing. In both cases filters select the necessary absorption bands. The cylindrical chopper Fig. 2 (not shown) rotates about its longitudinal axis which is perpendicular to a beam from a tungsten filament lamp and has two main passage-ways disposed at right angles to one another to pass the reference and sample beam alternately. Each has a narrower adjoining passage-way which extends over a greater arc of the cylinder and passes radiation to the switching photo-diodes. A plate placed after the cylinder has two main apertures to direct the reference and sample beams to the sample cells and two subsidiary apertures after which are placed the two switching diodes which only receive radiation from the adjoining passage-ways. The extended arc enables the switching signal beam to lead and trail the corresponding reference or sample beam and thereby ensure that the transistor switch feeds the correct channel for the whole of the time the corresponding reference or sample beam falls on the detector. An A.C. coupled amplifier is used which has a D.C. restoration circuit succeeding it.