GB163097A - Improvements in and relating to electrical measuring instruments - Google Patents

Abstract

163,097. British Thomson - Houston Co., Ltd., and Clinker, R. C. Feb. 9, 1920. Frequency, inductances, capacities, and resistances, measuring.- A movable coil in inductive relation to a fixed primary coil, but having no conductive connection therewith, is connected to a condenser, and takes up a position in which the natural frequency of its circuit is equal to the frequency of the current in the primary coil, no mechanical controlling- device being provided. Frequencies may thus be directly measured. If the primary coil is supplied with current of definite frequency, the instrument may be used for measuring an inductance placed in series in the circuit of the moving coil, or a capacity or resistance placed in shunt to the condenser, the scale being correspondingly graduated. As shown, the movable coil 3 and fixed coil 2 surround a curved iron core 1. A balance weight 11 may be provided, or the arrangement may be duplicated, the two moving coils which balance each other being in series with a single condenser. A straight core may be used if the moving coil is of large aperture. In another form, the moving coil surrounds an iron cylinder placed between eccentrically-curved pole faces of an electromagnet carrying the primary winding. In series with the moving coil in any of the forms described there may be connected an inductance, or an additional fixed coil on the core. The moving coil may be mechanically connected to one element of a second and variable condenser in its circuit so that either the capacity alone or both inductance and capacity vary. The instruments are suitable for making graphic records.