New instruments: capacitively coupled seismographs and accelerographs

Abstract

The need of great magnifications and the usefulness of galvanometric recording and linear damping has almost made obsolete the exclusively mechanical recording instruments. Several manufacturers still make some strong-motion instruments which mechanically record on smoked paper. But, in these seismographs the friction of the stylus on the paper is almost always very dificult to compute, and the damping system is never proportional to velocity, specially when the steady mass is great, since linear damping is impossible when viscous liquids and moving vanes submerged in them are used, or if they have pistons moving inside air-filled cylinders.