GB836172A - Improvements in differential re-fraction liquid level gauges - Google Patents

Abstract

836,172. Indicating liquid levels. YARNALL-WARING CO. Nov. 8, 1957 [March 14, 1957], No. 34911/57. Class 123(1) A differential refraction boiler waterlevel guage in which the water and steam columns appear to the observer as strips of contrasting colours and which is viewed from a considerable distance by means of an optical system for example, comprising parallel mirrors, consists of a body 20 provided with a wedge-shaped interior gauge space 21 between front and rear windows 24, 27 which are set at angle of preferably about 20 degrees to each other. Behind the rear window is an illuminator housing 28 mounting sealed spotlights 32 in front of which are mounted side by side red and green filters 34, 35. The light passing through the filters 34, 35 forms green and red bands 41, 46 which are refracted in the water space to be emitted as bands of parallel green rays defined by limits 42, 43 and parallel red rays defined by limits 47, 48, each band being bounded by diverging rays of the same colour. The light passing through the vapour space in the gauge is refracted through a different angle, the distance from the rear window to the filters being chosen so that a band of parallel red rays is emitted vertically above the band of green rays from the water space. The optical angle of pick-up by the optical system referred to above is made sufficiently narrow to receive only the vertically superimposed bands of exclusively parallel green and red rays so that the distant observer sees the water and steam spaces as bright green and red bands of light respectively.