GB353591A - Improvements in and relating to systems for indicating or repeating the movement of a member electrically - Google Patents

Abstract

353,591. Electric signalling systems. WARREN, T. R., Beechwood, Gaskell Road, Altrincham, Cheshire, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Bush House, Aldwych, London. May 21, 1930, No. 15692. [Class 40 (i).] The movements of a member, e.g. an electricity meter, are indicated or repeated through the intermediary of a photo-electric cell, the illumination of which is controlled by a shutter operated by the member and a second shutter adapted to follow the movements of the primary shutter. As shown in Fig. 1, the master pointer 1 moving over a scale 11 carries a shutter 2 having a recess 3 in the vertical edge, and being adapted to co-operate with a pair of shutters 4, 4<1> mounted on the pointer 6 of a follower instrument and having recesses 5, 51 which together with the recess 3 control the illumination of the photo-electric cell 9 by the light source 8. Between the cell 9 and the shutters is located a lens system 10 and a shield 12 having a divergent aperture 13 which allows the width of the aperture between the shutters to remain constant over the whole range of movement whilst providing variable illumination according to the extent of movement. The photo-electric cell 9 is connected to the grid of an amplifying valve 17, Fig. 2, the anode 21 of which supplies repeating instruments 23 and the following instrument 7 which may be of the moving coil type. When the primary pointer 1 alters its position the intensity of illumination of the cell 9 is changed and the current in the follower instrument 7 is varied to cause the pointer 6 to follow the pointer 1 until the aperture between the shutters is adjusted to an extent such that the illumination of the cell is sufficient to maintain the follower shutter in its new position. The shield 12 may be dispensed with if desired and a single shutter 4 may be employed. Modified amplifying arrangements employing two stages, Figs. 3, 4 and 5 (not shown), may be employed. Moreover alternating-current amplification may be employed, the light source being interrupted at constant frequency, e.g. by the use of a neon lamp supplied with alternating current.