deadbands

Deadbands, in control theory and engineering, refer to a range of input values within which the system does not produce a change in its output. This zone, also called a dead zone or no-action band, is used to prevent small input fluctuations, noise, or sensor jitter from causing unnecessary actuator movement or switching. Deadbands are distinct from hysteresis, though both are related to the response near the operating point; a deadband defines a region of no action, while hysteresis defines direction-dependent thresholds.

Deadbands can be implemented in hardware, such as relays and actuators with mechanical gaps, or in software and controllers, by introducing thresholds around a setpoint. They can be symmetric, having equal margins on either side of the setpoint, or asymmetric, with different activation and deactivation limits. In some contexts, the term deadband is used interchangeably with a no-action zone or neutral zone in proportional control.

Common examples include thermostats that turn heating or cooling on and off only when the temperature crosses the upper or lower bounds of a defined band, and motor controllers that avoid rapid chatter by ignoring small commanded changes. In measurement systems, deadbands reduce sensitivity to noise but can introduce steady-state error or lag.

Design involves choosing the deadband width to balance responsiveness against stability and wear. A wider deadband reduces cycling and noise-induced wear but increases steady-state deviation from the setpoint; a narrow deadband improves precision but risks chattering in noisy environments. See also: hysteresis, bang-bang control, and neutral zone.