What are the two main operating modes of a controller?

The two main operating modes of a controller are indeed automatic and manual. In automatic mode, the controller continuously monitors the process variable and makes adjustments based on feedback to maintain the desired setpoint. This is crucial for maintaining consistent process operation without human intervention.

In manual mode, the operator actively controls the process by adjusting the control elements, such as valves or pumps, based on their judgment or specific requirements at that time. This mode allows for more direct oversight and handling of the process, which can be beneficial in scenarios where precise control is necessary or during certain troubleshooting situations.

Automatic operation is essential for maintaining efficiency and stability in processes, especially in complex systems where constant adjustments are required. Manual mode serves as a critical backup or adjustment phase, offering operators the flexibility to intervene as necessary. This dual capability ensures both automated efficiency and operator control, essential for optimizing process performance and safety.