GB1113986A - Improvements in or relating to fluid analysis - Google Patents

Abstract

1,113,986. Lasers. HILGER-I.R.D. Ltd. 16 Sept., 1965 [19 June, 1964], No. 25448/64. Heading H1C. [Also in Division G1] An infra-red absorption analyser uses a laser as radiation source. A simple monobeam analyser is described with reference to Fig. 1 (not shown). In a twin-beam analyser for testing for CH 2 or CH 3 groups, Fig. 2, 3.39 Á radiation from opposite ends of a He-Ne gas laser passes through sample and reference chambers 26, 28 to detectors 32 of the type filled with the gas to be detected. The detector outputs are connected in opposition and the difference is displayed on the meter 36. Optical wedges 38 are provided; one for zero setting, the other for null balance operation, which may be automatic. The laser output may be modulated by pulsing the supply, tilting the laser or its mirrors or chopping the emerging beams. In a modification, Fig. 3 (not shown), the radiation beams after passing through the sample and reference chambers fall on the two gas chambers of a differential capacitor-type detector. In another modification, Fig. 4 (not shown), the beams are chopped in antiphase and fall on a single detector. The analyser may be used to detect small quantities of ethyl alcohol in exhaled air, or oil in water, and the type of laser, solid or gas, and its material is chosen to give a wavelength in the desired absorption band.