Human-Machine Interface (HMI)
A human-machine interface (HMI) is the operator panel or software through which personnel monitor and control a machine or process. Typically a touchscreen operator panel or a PC-based application, it displays process values, alarms, trends and equipment status, and allows set-point changes and start/stop commands. The HMI communicates with PLCs or other controllers over protocols such as Modbus TCP, PROFINET, EtherNet/IP or OPC UA. HMIs are used on machinery, packaging lines, pump skids and utility systems, while SCADA systems extend similar functions across multiple sites. Selection parameters include screen size and resolution, touch technology, front-panel IP rating (often IP65 or IP66), supported communication drivers, alarm and data-logging capacity, and operating temperature. Alarm management is guided by IEC 62682 and ISA-18.2, and display design by ISA-101.
Examples
- Touch panel on a packaging machine
- Pump skid HMI showing pressures and alarms
- PC-based HMI for a water treatment plant