Roadmap › Industrial Automation — PLC, SCADA, Modbus and OPC UA › Module: Supervisory Systems and Communication
Lessons in this course (10)
6. HMI, SCADA, alarms and historians
Intermediate★ Must knowLesson 6 of 10
- HMI (Human-Machine Interface) — operator screen for one machine or line: start/stop, setpoints, status, alarms.
- SCADA (Supervisory Control and Data Acquisition) — supervises many PLCs/RTUs across a plant or region (pipelines, water networks): data collection, control, alarms, trends, reports, often redundant servers.
- Alarm management (ISA-18.2): priorities, acknowledgement, shelving, avoid alarm floods; every alarm must require an operator action.
- Historian — time-series database storing tag values (temperatures, states) with compression for years; used for trends, OEE, investigations, batch reports.
- High-performance HMI (ISA-101): grey backgrounds, colour only for abnormal states, clear hierarchy of screens.
Tag = named data point (e.g. Line1.Filler.Motor.Running, Tank3.Level.PV) with type, address, scaling, alarms and history settings.