An HMI is the operator’s window into a machine: a touch panel on the cabinet that shows temperatures, alarms and buttons to start, stop or adjust. It reads live values from the PLC and writes setpoints back. Larger installations use SCADA screens in a control room, which are HMIs at plant scale.
The IoT blurs the line between an HMI and a dashboard. Web-based HMIs can now be opened on a tablet or a phone, and the same data that drives the panel is pushed to the cloud for analytics. That convenience raises the question of who may write to a controller from where, and good designs keep remote views read-only unless strong authentication and physical safeguards are in place.
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