GB494808A - Improvements in or relating to detachable electrical indicating instruments - Google Patents

Abstract

494,808. Current and voltage measurements ; two-part couplings. WESTING- HOUSE ELECTRIC & MANUFACTURING CO. Feb. 17, 1938, No. 4923. Convention date, March 20, 1937. [Classes 37 and 38 (i)] A detachable indicating instrument such as an ammeter, voltmeter, or wattmeter, is arranged so that the mounting of the meter on its support makes the proper circuit connections to the instrument movement. The casing comprises a base-plate 2, Fig. 2, and a transparent cover 4 clamped thereto by a sealing ring 6 and a gasket 8. Contact blades 10 project from the rear of the base for co-operation with fixed contact jaws by which the instrument is supported. Each blade 10 comprises a flat strip passing through a slot in the base and insulated therefrom by a member 12 on the interior of the base and a member 14 on the exterior formed with an upturned portion 16 to prevent the blade 10 from making contact with adjacent metal structures during insertion into the contact jaws. The inner portion of each blade 10 is provided with a screw 18 for making connections within the casing. An auxiliary base-plate 20, cut away to permit access to the screws 18, is supported on the inner face of the base 2 by spacing posts 22 and screws 23. The instrument shown is of the repulsion vane type having a winding 24 enclosing a chamber containing the fixed and moving vanes. The pointer 28 co-operates with a scale plate 32 which is spaced from the auxiliary base-plate 20, the auxiliary resistors, voltage multipliers, &c. required for calibrating the instrument being mounted on the plate 20 above the instrument movement and between the plates 20, 32. The side walls of the glass cover 4 are made translucent, as by painting or applying a coating 40. A number of different instruments may be adapted to engage a single set of contact jaws for making different measurements, for example, an ammeter winding 24, Fig. 3, is connected between an upper and a lower blade 10, the other two blades being short-circuited. Connections for a voltmeter are shown in Fig. 4, the winding 24 being connected in series with a resistance 44 as shown.