Actual elements in a control loop

Any deviation or difference between the two values will result in an output signal to the controller. The controller will then take action in a manner related to the deviation and provide a signal to a regulating unit. The regulating unit will then increase or decrease its effect on the system to achieve the desired value of the system variable

Feed back: This is the transmission of a signal representing the output

Closed loop control system : The system is one in which the control action is dependent on the output.

Measured values: Actual value of the controlled condition.