GB189923319A - Improvements in Electrical Measuring Instruments. - Google Patents

Abstract

23,319. Atkinson, L. B. Nov. 22. Current meters.-A glass or other float A, with a thin stem a, contains an iron or steel wire, and is movable in a closed vertical glass tube C by a surrounding coil E. The tube may be partly filled with water, ether, or other liquid, and contain air above this, the float being weighted to keep the stem upright. Or the tube may be filled with two immiscible liquids, and the stem placed downward. The float may carry a waterproof paper or other mark, or may be a cylinder with flat ends, in a coloured liquid, so that the position of either end may be observed on a scale G. The float may nearly fit the tube, to slow its movements. To correct for variations in density with temperature, the tube may be formed with a bulb or extension at its lower end, expansion of the liquid in this causing a compensating rise in the level of the top of the liquid. Or the tube may carry a thermometer K, and the scale G be moved vertically by hand until a mark N on it stands level with the top of the mercury column. Or the liquid used may be water saturated with ammonium sulphate or chloride, or other salt more soluble at higher temperatures, an excess of the salt being placed in the tube. The instrument may be used for measuring electromotive-force or current, or as a maximum current indicator, by adhesion of a coloured liquid to the stem. The Provisional Specification mentions the use for this purpose of a porous stem, removable to serve as a record.