A closed loop control system uses a sensor that feeds current system information back to a controller. That information is then compared to a reference point or desired state. Finally, a corrective signal is sent to a control element that attempts to make the system achieve its desired state.
A very basic example of a temperature control loop includes a tank filled with product (the process variable), a thermocouple (the sensor), a thermostat (the controller), and a steam control valve feeding a tubing bundle (the final control element).
The video outlines all the major parts of the system, including the measured variable, the set point, the controlled variable, controller, error and disturbance.
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