A PLC is the controller that executes machine logic, while SCADA is the supervisory layer that monitors and coordinates many PLCs across a facility. The PLC makes the real-time decisions; SCADA collects, displays and stores what those controllers are doing.
- PLC function: Reads inputs, runs the program and switches outputs in real time, with no supervisory layer required to function.
- SCADA function: Aggregates data from many PLCs and sites for plant-wide monitoring, alarming and reporting.
- Data exchange: SCADA reads PLC tags over an industrial protocol such as EtherNet/IP, PROFINET or OPC UA.
If SCADA goes down, well-programmed PLCs keep running the process because the control logic lives in the controller. Review the controller side of the system on of our PLC System Integrators for more information.
