What is a deadband and why is it used in control loops?

• A. The input range where output changes rapidly.
• B. The maximum output range of the actuator.
• C. The region where the controller saturates.
• D. The input range where no output changes; used to avoid chattering due to minor fluctuations and noise.

Answer: (D)

A deadband is the input range around the desired value where the controller output does not change, so the system ignores small errors or noise. This helps prevent the actuator from chattering or cycling on and off due to tiny fluctuations from sensors, noise, or measurement resolution. When the error is larger than the deadband, the controller starts to adjust the output to reduce the error; inside the deadband, the output stays put, maintaining stability and reducing wear on the actuator. The other options describe regions of rapid output change, full-scale output, or saturation, which are not what a deadband represents.