Deadband is a common phenomenon that refers to the range or width of a controller's output value that cannot cause a change in the measured process variable when the input signal changes direction. When a load disturbance occurs, the process variable deviates from the set point. This deviation will generate a corrective action by the controller and revert to the process. However, an initial change in the controller output may not produce a corresponding corrective change in the process variable. A corresponding process variable change will only occur if the controller output changes by a sufficient amount to overcome the deadband change. 

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