What component constantly compares input signals to the set point in a control system?

In a control system, the component that constantly compares input signals to the set point is the control loop controller. The primary function of this controller is to monitor the difference between the desired set point and the actual process variable, which is the input signal received from the system.

When the input signal deviates from the set point, the controller calculates the error between them and determines the appropriate control action needed to reduce that error. This may involve sending signals to final control elements—like valves or actuators—to adjust the process accordingly. By continuously monitoring and comparing these signals, the control loop controller ensures that the system maintains the desired performance and responds effectively to changes or disturbances in the process.

In contrast, other components like the final control element, stepper motor, and feedback loop have different roles. While the final control element executes the commands from the controller, the feedback loop conveys the actual output back to the controller but does not directly perform the comparison itself. The stepper motor may be part of the physical mechanism controlled but does not handle the comparison of inputs to the set point. Thus, the role of the control loop controller is essential for effective control system operation.