GB635072A - Improvements in or relating to electric rate measuring systems - Google Patents

Abstract

635,072. Frequency, voltage, current measurements. STANDARD TELEPHONES & CABLES, Ltd., DUNN, R. H., and LENNOX, P. W. Feb. 7, 1947, No. 3706. [Class 37] In an electric rate-measuring system, contacts IP are impulsed at a rate to be measured, e.g. by a k.w.h. meter, to alternately charge condenser C1 from a negative potential source and discharge it into a larger condenser C2 with which is associated an amplifier valve V1 having C2 as a negative feedback path between the anode and grid and effective to linearise the relation between increasing increments of charge from C1, and the charge on C2, which leaks through R12, R13 between increments of charge from C1. The voltage across C2 is fed to the grid of valve V2 after smoothing in a time constant circuit comprising resistances R9-R13, condenser C3 and rectifiers H1, H2 normally biassed to present a high resistance, which alternatively assume a low resistance when the charge on C2 changes, so that the grid voltage of valve V2 may rapidly follow changes in the rate of impulsing. The anode current of V2 flows in the opposed windings Al, A2 of saturable transformers T1, T2 and a steady direct current in the opposed windings D1, D2 enables the saturation to be adjusted so that the current from an A.C. source through series windings B1, B2 and the primary of transformer T3 is linearly related to the direct current in windings A1, A2. The secondary of transformer T3 is connected to a bridge rectifier, and the resultant D.C. deflects a measuring instrument M to indicate the quantity to be measured and regeneratively energizes the transformer windings E1, E2 to increase the amplification of the device. The rectifier output operates a summator S, which may record the aggregate of the indications of a number of devices of the kind described. Negative feedback to the grid of valve V1 is provided through resistance R7. The rectifier connections may be inverted if required. The system is particularly applicable to watt/hour meters or mechanical stokers impulsing electrical contacts, but is operable to measure any variable voltage applied to the grid of V2. Specifications 629,244, 629,245, 629,246, [Group XIX], and 629,260, [Group XL (b)], are referred to.