ABSTRACT
This chapter considers the actual implications of a control strategy and how it is affected by being applied to a real process environment. The causes of transfer lags are often complex, and, as a consequence, the plant response will in most cases be extremely difficult to calculate. Experimental analysis is the alternative; it can be employed in those instances when examination of the results of test measurements or trials gives a good idea of the process unit characteristics. Differential-pressure instruments using the force balance principle are extremely fast and provide very small transfer lags. Analytical instruments, in general, have the largest lags. These lags are inherent in the technique used to obtain the measurement, which by its nature demand time to complete.
