Abstract
The usual method of obtaining frequency-response measurements is described. The data obtained are reduced by visual inspection, but difficulties arise due to distortion and noise in the process. The range of frequencies over which measurements can be made is limited by noise and distortion and may prove inadequate for studying the stability of the process when controlled. These shortcomings may be overcome by methods of frequency-response measurement in which the data are reduced by means of a computer rather than by visual inspection. Two methods of frequency-response measurement using an analog computer for data reduction are described. Results are given of laboratory measurements on a dummy process and of field measurements on a real process. The advantages of computer reduction of the data are clearly demonstrated. The further advantages to be derived from digital computation rather than analog computation are indicated.
