What is an HMI and what are its main features?

HMI (Human Machine Interface) is the graphical interface between operators and control systems. Main features: process visualization (P&IDs, equipment status), setpoint entry and parameter adjustment, alarm display and acknowledgment, trend displays (real-time and historical), navigation between screens, and login/security levels. HMIs range from simple panel-mounted displays to complex SCADA workstations. Good HMI design follows ISA-101 guidelines for effective operator interaction and situational awareness.