In a control system, what does the controller compare with the process variable?

In a control system, the controller's primary function is to ensure that the process variable—the actual value of the system being controlled—achieves the desired value known as the setpoint. The controller continuously monitors the process variable and compares it to the setpoint. If there is a difference between the two, the controller calculates the necessary correction to minimize this error and achieve the desired behavior of the system.

The setpoint is the target value that the system should maintain, and the comparison is essential for maintaining control. This process enables the controller to make appropriate adjustments through the actuator to influence the process and ensure it follows the setpoint accurately.

Understanding this function is critical because it underpins the entire operation of automatic control systems in various applications, from temperature regulation in heating systems to speed control in motors. It emphasizes the importance of the setpoint in effective control system design.