An Analysis of the Galvanometer Amplifier and its Response to Alternating Electromotive Forces and Mechanical Vibrations

Abstract

A system which is representative of most practical galvanometer amplifiers is analysed and the response of the system to alternating e.m.f.'s and to mechanical vibration is determined. It is shown that the values of the circuit constants can be so chosen that the galvanometer movement is at least critically damped for all conditions of operation and that, for critical damping. the frequency response curve for the amplifier to applied alternating e.m.f.'s resembles that for the galvanometer alone but is expanded along the frequency axis by a factor which depends on the degree of feedback. Mechanical vibration with a component about the axis of the galvanometer cod produces an effect which is markedly increased by the provision of feedback.