GB744716A - Improvements in or relating to apparatus for continuously recording the distance of an object from a fixed point - Google Patents

Abstract

744,716. Photo-electric apparatus for recording cloud data. BRISTOL CO. Oct. 31, 1953, No. 30142/53. Class 40 (3). [Also in Group XIX] A system for continuously recording the height and density of the cloud ceiling above a given point comprises an A.C. excited mercury arc lamp 10 in a reflector to produce a modulated beam of parallel light directed vertically, a distant photo-cell in a housing 15 which continuously scans the path of the light beam and a recording device with a pen-carriage 29 driven synchronously with the scanning movements of the housing 15, the pen 41 being deflected substantially normally to the line of travel of the carriage in accordance with signals received from the photo-cell. The photo-cell amplifier is tuned to the modulation frequency and so does not respond to steady light and the pen movement also may be tuned to this frequency. Accordingly when light reflected by mist, cloud, &c., from the light beam affects the photo-cell, the pen makes an oscillatory mark the amplitude and length of which are dependent on the density and thickness of the cloud &c. Instead of moving the carriage proportionally to the angle of elevation of housing 15, which gives a scale crowded at one end, a mechanical linkage may be provided to give a linear relation between the carriage position and the point on the light path being scanned, Fig. 8 (not shown). Instead of a single pen making an oscillatory mark there may be provided a pair of pens carried by scissors arms, Fig. 9, which are moved apart by a cam 78 controlled by rectified signals from the photo-cell. A single pen may alternatively be controlled by a torque-motor fed with rectified signals, or by a shaded pole torque motor. The oscillatory pendriving movements may be moving-coil, moving iron or piezo-electric.