Frequency Response Characteristics of Recording Instruments

Simple and direct methods are presented for ascertaining the magnitude of errors which arise from the dynamic limitations of instrument movements, and which appear in records obtained with recording instruments. Charts are given from which the a-c steady-state response may be obtained directly from the undamped natural frequency (or period) and the relative damping. These two basic constants of a particular instrument may be measured readily by the simple test methods described. Proper damping is emphasized, and certain techniques are suggested by which the frequency response may be improved beyond that obtainable with optimum damping. A simplified analysis of servo-actuated recorders suitable for application work also is included. The methods and the use of the charts presented are illustrated by means of numerical examples.