Moving-Coil Galvanometers of Short Period and their Amplification

Abstract

A short-period galvanometer and photoelectric amplifier are described. Advantage is taken of the high speed by recording with a cathode-ray tube. Potential changes of a few microvolts in a circuit of low resistance can be measured in a few milliseconds to within 0.5%. At extreme sensitivity the mean uncertainty at any moment is about twice that due to the Brownian movements of the galvanometer coil. The drift of base-line is small.