GB667450A - Improvements in or relating to h.f. apparatus - Google Patents

Abstract

667,450. High frequency current and voltage measurements; current measurements with current transformers. STANDARD TELEPHONES & CABLES, Ltd. May 18, 1950, No. 12452/50. Class 37. A high frequency measuring arrangement comprises means for obtaining two D.C. voltages proportional respectively to the electric and magnetic fields set up at any given point by an energized conductor and means for measuring the sum of the said two D.C. voltages to obtain a measure of the energization of the conductor. In the embodiment shown a current transformer secondary encircles an energized aerial feeder 1 which forms the current transformer primary and the output voltage of the secondary is fed over a half-wave rectifier 5 and through a series resistor 10 to a D.C. meter 11 to produce on the latter a component of deflection proportional to the aerial current at the point of coupling of the secondary to the aerial feeder 1. The transformer secondary with the straight through primary or energized feeder 1 is surrounded by a metal electrostatic shield 13 which is connected to earth over a large capacitor 15 so that in effect a capacitative voltage divider is thus formed. The voltage developed across the capacitor 15 is.fed over a half-wave rectifier 16 and through a series resistance 17 to the meter 11 to produce in the latter a component of deflection proportional to the aerial voltage at the point of coupling of the secondary to the aerial feeder 1. The meter 11 may be calibrated to produce indications of aerial current and aerial voltage separately, with switches provided to cut-out separately the rectifiers 5 and 16. The rectifier 5 is connected across the secondary through a D.C. blocking capacitor 6 and a leakage path to earth for the latter is provided through a resistor 7. A de-coupling capacitor 12 is shunted across the meter 11 to short circuit interference A.C. components.