INDUSTRIAL AUTOMATION | Explain proportional controller process control action.

Proportional Controller: 

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Proportional controller is a device that produces an output signal proportional to the deviation/error. The proportional control action is a multi position type of controller action in which position of the correcting element is directly proportional to the deviation. It is called as P control action. This action responds to the size and sign of deviation. For each value of deviation, there is a specific value of controller output of controller that correlates with a specific value opening. The proportional band is the range of deviation, in percent scale; that corresponds to the full range of deviations. It is dependent on the gain. The proportional controller amplifies the error signal by Kp.  Mathematically the controller output Po for proportional controller is expressed as, 

Po = Kp.ep + Pn

Where,  Kp is proportional constant, 

                        Pn is controller output with no error 

                        ep is error expressed as percentage of span