Abstract
The practical frequency-response analysis of two types of chemical-plant units, and the adjustment of the automatic controllers, are described. Available information on the magnitude, form, and location of disturbances is used to illustrate the effect of these factors on the quality of control actually obtained, and to emphasize that these factors are at least as important as the over-all characteristics of the plant. Even when all information on the disturbances is available, their effect on the quality of automatic control is not always easy to calculate, especially if the system has distributed parameters, but a description is given of an approximate calculation method which yields results of the right order of magnitude in many practical cases.
