GB583451A - Improvements in and relating to electric phase-comparing circuits - Google Patents

Abstract

583,451. Phase difference measurements. BRITISH THOMSON-HOUSTON CO., Ltd Oct. 30, 1944, No. 21199. Convention date, Oct. 28, 1943. [Class 37] A phase-comparison arrangement in which both input circuits are grounded, comprises lagging and leading phase-shifting networks across each input circuit, centretapped decoupling impedances connecting the lagging output terminal of each network to the leading output terminal of the other, square-law detectors for each centre-tap voltage, and means for subtracting the detected voltages. One input 1, 1<1> is applied to a phase-retarding network 7, 5 and to a phase-advancing network 8, 6, and the other input 2, 2<1> to a phase-advancing network 8, 5 and a phase-retarding network 6, 7. The output terminal 9 is connected to the output terminal 12 through resistances 13 the centretap of which is connected to a detector 17. Similar connections are made from output terminals 10, 11 to a reversely-poled detector 18, the detectors having condenser-shunted load resistances 19, 20. D.C. voltages of opposite sign are developed across the condensers 19, 20 and their difference, available between the terminal 21 and earth, is proportional to the sine of the phase angle between the inputs at 1, 1<1> and 2, 2<1>. Preferably the reactances 7, 8 are equal to each other and to the resistances 5, 6, so that the phase shifts are of 45 degrees. Capacities between leads &c. may be tuned out by inductance coils 22-25.