What does a control loop controller do?

A control loop controller is essential in industrial control systems, where it constantly compares the process variable, which is the measured value of a condition (like temperature, pressure, or flow), against a predetermined set point. The primary function of the controller is to ensure that the process variable remains as close as possible to the set point, thereby maintaining the desired operation of the system.

When the controller detects a deviation from the set point, it takes action to correct that deviation by adjusting the manipulated variable, which affects the process. This ensures the system operates within its desired range, improving efficiency and stability.

The other options refer to related functions but do not encapsulate the primary role of the controller in the context of a control loop. While the controller may send signals to primary elements and interact with manipulated variables, its core responsibility lies in the continual comparison of the process variable to the set point to facilitate appropriate adjustments. This ongoing comparison is critical to maintaining system performance and reliability.