ABSTRACT
The technology of process instrumentation continues to grow in both application and sophistication. In 1774, James Watt employed the first control system applying feedback techniques in the form of a flyball governor to control the speed of his steam engine. Dead time is rarely found in its pure form, but occurs frequently in combination with resistance-capacitance and other types of lags. Dead time is a difficult factor to equate when applying control to the process. The measuring element is connected to the control element. In many installations, the measurement is located far from the controller. Measuring transmitters have attained great popularity in the process industries. They perform the measurement and develop a pneumatic or electric signal proportional to the variable in one unit. Several principles associated with feedback control can be observed by considering a familiar control situation— adjusting the temperature of water in a bathtub. This is obviously a manually controlled system.
