A factory proportional-integral-derivative controller (PID controller or a three-term controller) is a control loop mechanism employing feedback widely used in industrial control systems and a variety of other applications requiring continuously modulated control. PID controllers are the workhorse of modern process control systems, as they automate regulation tasks that otherwise would have to be done manually. The control task done by the operator is called feedback control because the operator changes the firing rate based on feedback from the process via the temperature gauge. To explore the application of PID controllers to the room temperature and humidity control system, a factory engineer can consider a single-zone cooling system, as shown in the attached diagram.
