What is the primary purpose of a controller in automation?

The primary purpose of a controller in automation is to process error signals and command actuators. In a control system, the controller receives feedback from system sensors about the current state of the process (such as temperature, pressure, flow, etc.) and compares this information to the desired setpoint. When there is a difference, known as an error, the controller computes the appropriate response and sends commands to the actuators to adjust the system accordingly. This feedback loop is crucial for maintaining the desired operating conditions and ensuring the system operates efficiently and effectively.

The other options involve important functions in an automation system, but they do not capture the core role of the controller. Measuring system outputs directly is typically the function of sensors, while displaying user interface information pertains more to Human-Machine Interfaces (HMIs). Calibrating sensors is essential for accuracy in measurements, but it does not relate directly to the controller's main task of managing process control through feedback and adjustments.