HMI (human-machine interface)

An HMI can be a touchscreen on a machine, a panel in a plant, or software on a control-room computer. It shows process state, accepts commands and presents alarms. The ANSI/ISA-101.01 standard covers HMI design for process automation, promoting principles such as subdued graphics in which color highlights abnormal conditions, consistent navigation and displays organized around operator tasks; ANSI/ISA-18.2 covers alarm management.

For a product company, the HMI is often the only part of a complex system the customer sees. Clear states, confirmations for consequential actions, role-based access and disciplined alarm design prevent costly mistakes.