ELECTROMETER

n. E-leak-troam'eat-u6r. From ^txTpov (see ELECTRICITY), and nerpov. a measure. Fr., electrowetre. Ger., Elektrometer, Blitzstoffme er. It., elettrometro. Sp., electro metro. Any instrument for detecting the presence or measuring the quantity, intensity, etc., of an electrical current. [A, 518; L. 50.] Absolute e. A standard galvanometer or ammeter. [<", 27.] See AMPERE METER and MIIXIAMPEREMETER. Attracted disc e. See Quadrant e. Capillary e. An instrument for measuring the intensity of an electric current, or more exactly the difference in the potential of its two electrodes. Lippmann's model is almost exclusively employed. It consists of a vertical tube drawn out to a point at its lower extremity and containing a column of mercury which descends into the narrow tubular part until it is arrested by capillary resistance. The point is plunged into a test-tube containing a layer of a dilute solution of sulphuric acid. By uniting the two bodies of mercury by a platinum wire, the capillary column becomes fixed in position, its lower meniscus representing the zero of the apparatus. The intensity of an electro-motor force interposed in the closed circuit can be measured by a micrometric reading of the extent of the upward or downward displacement of the inferior mercury meniscus. The displacement is due to the fact that the capillary constant of mercury when in contact with sulphuric acid varies with the electrical condition. [L, 87 (a, 27).] Quadrant e. An instrument invented by W. Thomson to measure the potential of electricity of a body or the difference in the potentials of two bodies. It consists of a box composed of four equal horizontal and isolated metallic sectors, the diagonal members being coupled and of the same potential. A metallic plate is E, he; Ea, ell; G, go; I, die; Ia, in; N, in; Na, tank; [s. 672]