What does dead time refer to in a control system?

In a control system, dead time refers specifically to the time delay between the point when a change is made to the input of the system and the point when the output begins to respond or change as a result of that input. This concept is crucial for understanding the dynamic behavior of systems, as it can significantly affect the performance and stability of control systems.

When an input variable is altered, whether it's a setpoint change or a disturbance, the output does not instantaneously reflect that change. Instead, there is a period of inertia – or dead time – during which the output remains unchanged before it starts to move towards a new value. This characteristic is vital for control system design and tuning, as excessive dead time can lead to difficulties in achieving desired performance, potentially resulting in overshooting, undershooting, or oscillations in the output.

Understanding dead time helps technicians and engineers in selecting appropriate control strategies, such as PID tuning, to mitigate the impacts of this delay and enhance system stability and responsiveness.