Frequency response of recording instruments

THE DYNAMICS of common types of instrument movements have been studied a great deal, but information dealing with this subject has not been available readily in a form suitable for application work. The behavior of most instruments can be defined by a second order differential equation. In this case the frequency response characteristics can be expressed in terms of the undamped natural frequency and the relative damping. Curves can be plotted in terms of these two parameters to provide a simple and direct method of predicting the magnitudes of instrument errors so that one may decide whether a particular system is satisfactory for a given application, and if so by what margin. The frequency of the signal is expressed as a fraction of the undamped natural frequency of the instrument in order that the curves be applicable universally.