Glossary · HMI, SCADA and operations
Human-machine interface (HMI)
Also known as: HMI, Man-machine interface (MMI), Operator interface
German: Mensch-Maschine-Schnittstelle (HMI)
In industrial automation, a human-machine interface (HMI) is the collection of screens, hardware and software through which operators and other users monitor and interact with a machine or process control system.
- HMI and SCADA
- Standards
In one sentence
An HMI is the screens, hardware and software through which operators monitor and control a machine or process.
Example
On the HMI of a filling machine, the operator selects the product, starts production, watches the fill level trend and acknowledges alarms.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Engineering: ANSI/ISA-101.01 describes an HMI lifecycle with a style guide, display hierarchy and consistent use of color, reserving strong colors for abnormal states. Good HMI design reduces Human error and supports situation awareness.
- Operation: The HMI is where operators see alarms, trends and faceplates. It is also where interlocks and access control become visible to them.
- Safety: An HMI screen button is generally not a safety-rated control device; emergency stop, for example, is a separate hard-wired function. Messages on the HMI support but don't replace safety information in the instructions.
- Documentation: Operating manuals should mirror the HMI structure and use its exact labels. Coordinate HMI texts and manual terms through one terminology database, and review screenshots at each software release.
HMI vs. SCADA
An HMI is the operator interface of a machine or system. Supervisory control and data acquisition (SCADA) adds supervisory functions across many controllers or sites, such as data acquisition, historians and remote communication; it includes HMI functions.