What does automatic control in a controller describe?

Automatic control in a controller refers to the system's ability to manage the final control element based on an error signal. This means that the controller continuously monitors the output of a process and compares it to a desired setpoint. When there's a difference, or "error," between the actual output and the setpoint, the controller adjusts the final control element—such as a valve or actuator—to minimize this error and maintain system stability.

This feedback loop is essential for maintaining desired operating conditions automatically without the need for manual intervention, which ensures the process operates efficiently and effectively.

Other options involve manual or localized control mechanisms that do not embody the essence of automatic control. For instance, manipulating a final control element by an operator suggests a level of manual control that does not rely on automatic adjustments, while a final element controlled by a local setpoint lacks the responsive nature characteristic of automatic control—instead potentially functioning in isolation. Additionally, while a controller receiving a setpoint from remote may describe certain configurations, it does not inherently express how automatic controls fundamentally operate through error correction and feedback mechanisms.