GB810580A - Improvements relating to rate measuring apparatus - Google Patents

Abstract

810,580. Analogue electric calculating. ELECTRIC & MUSICAL INDUSTRIES Ltd. June 14, 1951 [June 23, 1950], No. 15694/50. Class 37. To measure the rate of change of amplitude of a first A.C. voltage y, a second A.C. reference voltage x is multiplied by a factor having a constant rate of charge and the amplitude of x is adjusted so that the product is equal to the rate of change of y. The amplitude of x is thus proportional to the rate of charge of y. In the circuit, signals of the form y + zx are first derived for different values of z, the circuit parameters being such that the rate of charge of z is - 1. Then the y + zx signals are applied to differentiating circuits the outputs of which are of form y -x + zx. Each differentiating circuit corresponds to a separate value of z and the output corresponding to z = 0 is chosen and automatically adjusted to be zero by changing the value of x, the amplitude of which represents the instantaneous rate of change of y. As shown, the reference voltage x is derived at tapping 3 of auto transformer 2, and a number of differing zx voltages are derived at the tappings 8-12. The voltages at 8-12, that is y + zx, are separately differentiated at 13-22 and those derived from tappings near 29, that is where z = 0, are applied over scanning tappings 23-27 to the auto transformer 28 the output of which is thus y x. This signal controls the setting of tapping 3 so as to render y - x = 0 and the position of 3 or 2 is a measure of y.