Galvanometer efficiency as a design parameter

IN THE ordinary use of a galvanometer, its response to a small voltage in a closed circuit is almost always the point of interest; its action can only be completely understood if the galvanometer is considered as a circuit element. The response of a galvanometer in the detector branch of a bridge or potentiometer circuit informs the operator of the direction and magnitude of the adjustment he must make to reduce the unbalance of the network. Reduced to its simplest terms, the galvanometer sees a certain resistance connected across its terminals in which a certain electromotive force (emf), the unbalanced voltage in the network, is present. The galvanometer acts in all respects like an electric motor which stalls after winding a spring (the galvanometer suspension). The useful work is represented by the energy stored in the suspensions of the deflected instrument. It is therefore proper to inquire what use the galvanometer makes of the power available at its terminals,1 and what means can be used to make it utilize this power efficiently in its motor action.