What is the purpose of a deadband in a control loop?

• A. To reduce sensor noise
• B. To prevent frequent on/off cycling by allowing a small range around the setpoint before actuation
• C. To increase energy consumption
• D. To simplify control logic

Answer: (B)

A deadband creates a no-actuation zone around the setpoint. Its purpose is to prevent the controller from switching the actuator every time the process variable wobbles near the target. Inside the deadband, no action is taken; only when the variable moves beyond the upper or lower threshold does the actuator respond. This reduces rapid on/off cycling, which lowers wear on switches and valves and saves energy by avoiding unnecessary actuation. For example, with a setpoint of 22°C and a deadband of ±0.5°C, the heater turns on when the temperature falls to 21.5°C and turns off when it reaches 22.5°C, so small fluctuations inside that 21.5–22.5°C range don’t cause constant switching. While deadbands can mildly affect responsiveness, the main benefit is stability and reduced chatter around the setpoint.