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

• A. A large range around the setpoint where actions are intensified.
• B. A small range around the setpoint where no action occurs.
• C. A method to rapidly correct errors.
• D. A type of sensor calibration.

Answer: (B)

A deadband is a small range around the setpoint where the controller does not take any action. It’s used to prevent reacting to tiny fluctuations or sensor noise, which would cause frequent, unnecessary switching of the actuator. Instead, the system remains idle inside this band and only starts correcting when the error exceeds the band. Once outside, corrective action is taken until the process value returns to within the band, then action stops again. An everyday example is a thermostat: the heater turns on when temperature drops below the lower edge and turns off only after the temperature rises above the upper edge, avoiding constant on/off cycling in between.