Direction: In many of the process control applications, the purpose of control system is to keep the output (controlled variable) almost constant in spite of changes in load. Mostly in continuous processes the set point remains constant for longer time. Such an operation is called 'Regulator Operation'. The set point generated, and the actual values from sensors are given to a controller. The controller compares both the signals, generates error signal which is utilized to generate a final signal as controller output. The controller output is finally utilized to physically change the values of manipulated variable to achieve stability. The above action is achieved with the help of final control elements. They are operatable either with electrical, pneumatic or with hydraulic signals. The system that serves good for servo operation will generally not be the best for regulator operation. Large capacity or inertia helps to minimize error here, whereas it makes the system sluggish in case of servo operation.