An HMI is the machine-level interface an operator uses on one line, while SCADA supervises devices across an entire facility. SCADA adds centralized reporting, a data historian and facility-wide alarm management, and it can sit above many HMIs at once.
- HMI scope covers one machine or line, with local visualization and control at the point of work.
- SCADA scope covers the whole facility, pulling data from many HMIs, PLCs and remote sites into one supervisory layer.
- Data historian inside SCADA stores months of time-stamped process data for trend analysis and compliance reporting.
If a line-level HMI goes offline, SCADA still logs and alarms on the underlying PLC data it collects. Consider the operator-interface side of the system on our HMI page.
