What is ISA-101?
ISA-101 (ANSI/ISA-101.01-2015) is the International Society of Automation standard for designing, building and managing HMIs in process automation systems, with the aim of letting operators quickly understand the process state and recognise deviations in time. The standard was published in 2015 and complements ISA-18.2 for alarm management. ISA-101 does not prescribe colours or displays, but a lifecycle and principles with which an organisation sets up its own consistent HMI standard. The best-known application of it is the high-performance HMI.
🧠 Why was ISA-101 created?
Until around 2010, HMI displays were often designed as colourful, photorealistic images of the installation, with lots of numbers and moving elements. Research by, among others, the ASM Consortium (Abnormal Situation Management) showed that operators using such displays notice deviations more slowly. Accidents were partly caused by crucial information failing to stand out. ISA-101 brings the insights from that research together in a standard.
🔧 What lifecycle does ISA-101 describe?
| Stage | Content |
|---|---|
| HMI philosophy | Principles and goals of HMI design for the whole organisation |
| Style guide | Concrete rules: colours, symbols, fonts, navigation, display layout |
| Toolkit | Reusable objects and templates in the HMI software |
| Design | Operator task analysis, display hierarchy, content per display |
| Implementation | Building, testing and training |
| Operation | Daily use, operator feedback |
| Continuous work processes | Management of change, periodic audits, improvement |
📊 What are the principles of a high-performance HMI?
| Principle | Application |
|---|---|
| Grey background | Calm picture; colour is reserved for deviations |
| Colour means something | Red and yellow only for alarms; never for normal states such as “motor running” |
| Information in context | Analogue indicators with a normal range instead of bare numbers |
| Display hierarchy | Level 1 overview, level 2 process area, level 3 detail, level 4 diagnostics |
| Trends on the display | Embedded trends show whether a value is rising or falling |
| Consistency | The same symbols and navigation on every display and in every installation |
| Little decoration | No 3D effects, animations or photos that distract attention |
A practical rule of thumb: on a good level 1 display, an operator can see within seconds whether the installation is running normally, without having to read numbers.
🔄 How does ISA-101 relate to ISA-18.2?
ISA-18.2 determines which alarms exist, with what priority and what action. ISA-101 determines how those alarms and the other process information are shown on the display. Together they form the basis for good situational awareness in the control room. A high-priority alarm from ISA-18.2, for example, gets a fixed colour, shape and position in the ISA-101 style guide.
❓ Frequently asked questions
What is a high-performance HMI?
A high-performance HMI is an HMI design following the principles of ISA-101 and the ASM Consortium, with grey backgrounds, colour only for deviations and information in context. The goal is that operators notice deviations sooner and make better decisions. Research showed that operators using such displays detect deviations clearly earlier than with traditional colourful displays.
Why are HMI displays grey under ISA-101?
HMI displays are grey under ISA-101 so that colour is used only to indicate deviations. If a display is full of colours, a red alarm stands out less. A grey base display ensures that the operator’s attention is automatically drawn to the deviation. Grey is also less tiring during long periods of viewing.
Is ISA-101 mandatory?
ISA-101 is a voluntary standard. More and more owners of process installations include it in their specifications for new or modernised control systems. When migrating a DCS or SCADA system, it is a logical moment to redesign the HMI in line with ISA-101.
What does an HMI style guide contain?
An HMI style guide under ISA-101 describes concrete design rules: which colours for which states, which symbols for pumps, valves and tanks, font sizes, display layout, navigation, and how alarms and trends are shown. The style guide ensures that all displays in an installation look the same, even if different parties built them.
How do you start an ISA-101 project?
An ISA-101 project usually starts with an HMI philosophy and a style guide, drawn up with operators, process engineers and the HMI supplier. A reusable toolkit is then built and displays are redesigned per process area, often starting with the level 1 overview displays, which deliver the biggest gain in situational awareness.
What are the four levels of an HMI display hierarchy?
An HMI display hierarchy under ISA-101 usually has four levels. Level 1 gives an overview of the operator’s entire span of control, level 2 shows a process area for normal operation, level 3 the details of a single device or control loop, and level 4 diagnostic and supporting information. This lets the operator navigate from overview to detail.
What is the difference between ISA-101 and EEMUA 201?
ISA-101 is the US standard for HMI design in process automation. EEMUA 201 is a British guideline from the Engineering Equipment and Materials Users Association on the design of operator interfaces and control rooms. Both share the same principles, such as a display hierarchy and sparing use of colour; EEMUA 201 also pays more attention to control room layout.
📌 In summary
ISA-101 is the standard for HMI design in process automation, with a lifecycle from philosophy and style guide to management, and the basis for high-performance HMI with grey displays and colour only for deviations. Together with ISA-18.2 for alarm management, ISA-101 helps operators see deviations sooner and intervene better.