On Methods of Varying the Sensitiveness of Ballistic Galvanometers

Methods of changing the sensitiveness of ballistic galvanometers in a definite ratio by the use of shunt resistance.—When a condenser is discharged through a ballistic galvanometer and then the same discharge is used with the same galvanometer when shunted, the ratio of the throws depends partly on the reduced charge going through the galvanometer and partly on the damping produced by the shunt. General formulas for this ratio have been obtained in terms of a galvanometer constant $m_0$ and the ratio $n$ of the shunt resistance to that of the galvanometer. If it is desired to reduce a given throw to either one-fifth or one-tenth of the original value, the shunt resistance required for this purpose may be obtained from a table, which is given, provided the resistance of the galvanometer is known, and also the shunt resistance required to reduce a given throw to one-half, which is readily found by trial.