GB190905413A - Improvements in Apparatus for Measuring Alternating Electric Currents. - Google Patents

Abstract

5413. Guggenheimer, S., and Gossen, C. March 5. Thermal current-meters. -Alternating currents or pressures are measured by causing them to warm thermo-electric couples e arranged in bridge connexion, each branch d c l, d m l, Fig. 4, containing not more than two couples in series. The alternating pressure is applied to the points c, m. The couples are formed of wires, for instance of manganin and constantan, of about 0À1 mm. diameter, and produce a sufficiently high thermo-electric power to actuate an ordinary portable galvanometer or similar measuring-instrument g. Adjustable resistances r, r<1> enable the points l, d to be rendered equipotential with respect to the alternating current, and the points c, m equipotential with respect to the direct current generated by the thermo-couples e. The electromotive-force acting on the galvanometer g may be balanced by a known electromotive-force tapped from a resistance F in series with a cell E. A known variable resistance W enables the alternating current flowing through the bridge to be reduced when measuring a high electromotive-force between mains a, b. The two thermo-couples in one branch between the points m, c may be replaced by resistances, or the connexions shown in Fig. 3 may be employed, resistances n being placed in the alternating-current circuit.