GB452440A - Improvements in and relating to electrical measuring instruments and relays - Google Patents

Abstract

452,440. Current and pressure meters. NALDER BROS. & THOMPSON, Ltd., 97, Dalston Lane, and LIPMAN, C. L., 9, Stamford Grove East, Stamford Hill, both in London. Feb. 21, 1935, No. 5620. [Class 37] [See also Group XXXVII] A moving-coil instrument or relay has a magnet with a coercive force at least as high as 150 oersteds, the moving coil embracing a member of soft magnetic material such as soft iron fitted to one or both poles of the magnet. An external yoke may surround the magnet and coil to provide a flux return path, and this yoke may be formed in part by an adjustable permanent magnet. The yoke, main magnet and coil may be adjusted in the direction of the coil axis, and may be formed as a detachable unit in the external yoke or equivalent casing. The inner permanent magnets may have fixed windings, or carry short-circuited loops. The magnet may comprise an aluminium - nickel or aluminium-nickel-cobalt alloy. The moving- coil instruments can be employed with lightsensitive cells as exposure meters, and with asymmetrically conducting rectifiers for A.C. measurements. Polyphase instruments are provided with magnetic shielding between the elements. The magnet N, S, Fig. 1, may be semicylindrical, spherical or U-shape, soft iron pieces IN, Is being fitted to the poles and embraced by the moving-coil C. In Fig. 4, the coil embraces the soft magnetic material IN which may be shaped to give a uniform or non-uniform scale. Fig. 5 shows two moving- coils C1, C2, the flux return paths including adjustable magnets N<1>, S<1>, N", S". Such an arrangement may function as a ratiometer. In Fig. 6, the magnets are prisms held in position by a non-magnetic spacer B<1>. U-, C- or H -shape magnets may be employed. Fig. 11 shows a two coil instrument, the coils C, C embracing the soft magnetic material IN, I<1>N and Is, I<1>S and being connected in series or parallel. Fig. 13 shows a four-coil instrument, the coils C 1 ... 4 being connected for measuring the summated load of two or more circuits or the total load on a three-phase network. Series or parallel connection of the coils may be made and the coils may be wound on aluminium formers.