GB1147496A - Galvanometer - Google Patents

Abstract

1,147,496. Electric meters; indicating apparatus. INTERNATIONAL STANDARD ELECTRIC CORP. June 16, 1967 [June 17, 1966], No.27789/67. Headings G1J and G1Q. The coil 1 of a moving coil galvanometer is torsionally suspended, at least one end (as shown the top end) of the coil being secured to the inner end of a torsion band or wire 2 whose outer end is secured to a fixed support 3. The latter has a curved portion which is tangentially engaged by the torsion band at a point on the coil's axis of rotation, the band beyond this point being wrapped around the curved portion and secured to a portion off the axis: the band is secured to the coil by wrapping the band round a cylindrical pin 7 Figs. 2 and 4 (not shown), carried by a fitting attached to the coil. The other (lower) end of the coil is preferably secured to a second torsion band in a like manner. The or each support 3 is made of resilient material so that the suspension may be pre-tensioned before securing the band to the support, and the upper and lower supports may be relatively rotated to impart torsional pre-tension to the suspension. The coil rotates in the space between a hollow cylindrical yoke 11 and a core magnet consisting of a diametrically magnetized cylinder 12, Fig. 5, to which are secured polepieces 10, 10'. The gaps 35, 36 between the edges of the polepieces are disposed in line with ferromagnetic screws 20, 20' which are a clearance fit in respective radial holes in the yoke 11 and are gripped between insulating members 17, 19. These members are held tight against screws 20, 20' by the screws 15, 18 which also hold the assembly together. The screws 20, 20' are radially adjusted to vary the instrument sensitivity. The pointer 21 has a detachable tip in the form of a plastic sleeve and carries balance weights 24, 25 (not shown, but diametrically opposite weight 24) and 26. Each of these weights is a wire helix adjustable by rotation in the manner of a screw thread, a projection 33, Fig. 3, on each of the weight-carrying arms being gripped between adjacent turns of the corresponding helix.