Override (selector) control
Two or more controllers sharing one output through a selector, so the limit that matters most wins.
What it means
Override control, also called selector or auctioneering control, lets several controllers share one output through a low-select, a high-select or other logic. Each controller has its own measurement and its own setpoint, and the selector decides which one drives the output at any moment.
The structure exists so a limit can protect the process. The temperature controller on a heater runs the fuel valve most of the time; a fuel-pressure controller with a high-select takes over the moment the pressure limit is threatened, and hands the valve back when it is not. One is the regulating controller, the other is the override.
The failure modes live in the transfers. A controller that sits idle for hours winds up while its error accumulates, so it needs anti-reset windup that engages while it is not selected; and the handoff has to be bumpless, or the process takes a step every time the override trips.
Related
Where this comes up
Last reviewed 2026-09-18.