GB319744A - - Google Patents

Abstract

319,744. British Thomson-Houston Co., Ltd., (Assignees of Faus, H. T.). Sept. 27, 1928, [Convention date]. Void [Published under Sect. 91 of the Acts]. Electromagnetic current and pressure meters. - An electrical measuring instrument, particularly a voltmeter for a radio receiving set is provided with a flat coil 13, Figs. 1 and 2, moving in a strong magnetic field in the airgap between one pole of a permanent magnet 10 and a magnetic pole-piece 12 connected to the other pole of the magnet. The coil 13 is wound with fine wire on a flat spool having aluminium side pieces 14, 15 connected by a rivet 16. The ends of the coil are connected to the upper and lower pivots 17, 18, which are insulated from one another by being inserted in an insulating rod 19. The upper and lower bearings may comprise phosphor bronze or other metal cups 21, the upper bearing being held by a spring leaf 22. The coil 13 is connected, through the pivots 17, 18 and bearing 21 in series with high resistance spool mounted in the back of the case. The coil 13 may be arranged to move into or out of the magnetic field or the instrument may have a central zero. Counter torque is provided by means of an oblong magnetic vane 26, Figs. 2 and 4, on the shaft located between the poles 32, 33 of a magnetic diverter which is fed by magnetic members 34, 35 extending beneath the pole tips of the magnet 10. The pole pieces 32, 33 are mounted on a non-magnetic plate 36 which may be rotated for adjusting the zero. An alternative form of bearing is shown in Fig. 3, in which a polished stone bearing plate 28 is held in a metal housing 29. Above the stone 28 is a small-quantity of mercury 30 held in place by a washer 31.