A fundamental concept in process control where a sensor, controller, and actuator work together to regulate a physical process. In a closed-loop system, a sensor measures a process variable (like temperature), the controller compares it to a desired setpoint, and if there’s a difference it sends a command to an actuator to correct it. This loop continuously “feeds back” so the process stays on target. (Example: a thermostat (sensor/controller) measuring room temperature and turning a heater (actuator) on/off to maintain the set temperature.)
