Explanation : Basic : Proportional control is one in which the process input is change in direct proportion to the error(t) controls the output so that the manipulated variable and the error has proportional relation. The controller set the manipulated variable in proportion to The difference between the set point SP and the measured variable MV. The variable to be controlled, e.g. speed of a motor. Higher the difference, more is the change in the manipulated variable. The coefficient of deviation is called proportional gain, Kp and is mathematically written as:
Diagram :
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The controller is effectively an amplifier with a constant gain having certain range called as appropriate band. The proportional control action is used where the position of the final operator is determined by the relationship between the MV and SP reference value called as error Given as :
Error = SP - MV