HMI screen layout principles in SCADA systems - Deep Dive

Overview - HMI screen layout principles

What is it?

HMI screen layout principles are guidelines for designing the visual interface of Human-Machine Interfaces (HMI) used in industrial control systems. These principles help organize information and controls on screens so operators can understand and interact with machines easily and safely. The goal is to make the screen clear, intuitive, and efficient for monitoring and controlling processes. Good layout reduces errors and improves response time.

Why it matters

Without good HMI layout principles, operators may struggle to find important information quickly, leading to mistakes or slow reactions that can cause safety risks or production losses. Poorly designed screens can overwhelm users with clutter or confusing controls. Applying these principles ensures that critical data stands out and controls are easy to use, which improves safety, efficiency, and reduces downtime in industrial environments.

Where it fits

Learners should first understand basic human factors and ergonomics, as well as the fundamentals of SCADA and industrial control systems. After mastering HMI layout principles, they can learn advanced topics like alarm management, dynamic graphics, and user customization in SCADA systems.

Mental Model

Core Idea

An effective HMI screen layout organizes information and controls clearly and logically to support quick, accurate operator decisions.

Think of it like...

Designing an HMI screen is like arranging a kitchen: the most used tools and ingredients are within easy reach and clearly visible, while less important items are stored away to avoid clutter.

┌───────────────────────────────┐
│          HMI SCREEN            │
├─────────────┬─────────────────┤
│ Status Info │ Control Panel   │
│ (Critical)  │ (Buttons, Sliders)│
├─────────────┴─────────────────┤
│       Navigation & Alarms     │
│ (Easy access, clear alerts)   │
└───────────────────────────────┘

Build-Up - 7 Steps

1

Foundation

Understanding HMI Purpose and Users

Concept: Learn what an HMI is and who uses it to control industrial processes.

An HMI (Human-Machine Interface) is a screen that shows machine status and lets operators control equipment. Operators need to see important data quickly and act safely. Knowing the users’ needs and tasks helps design better screens.

Result

You understand why HMI screens exist and who they serve.

Understanding the user and purpose is the foundation for any good design; without it, layouts may not meet real needs.

2

Foundation

Basic Visual Hierarchy Concepts

Concept: Learn how to arrange screen elements so the most important information stands out.

Visual hierarchy means making critical info bigger, brighter, or placed where eyes naturally go first. Less important details are smaller or in secondary areas. This guides operators to focus on what matters most.

Result

You can identify and prioritize key information on a screen.

Knowing how to guide attention prevents operators from missing critical alerts or data.

3

Intermediate

Grouping Related Controls and Information

Concept: Learn to organize related items together to reduce confusion and speed up use.

Group controls and data by function or process area. For example, all temperature controls in one section, all alarms in another. Use borders or spacing to separate groups visually.

Result

Screen elements are logically arranged, making navigation easier.

Grouping reduces cognitive load by letting operators find related items quickly without searching.

4

Intermediate

Consistent Use of Colors and Symbols

🤔Before reading on: do you think using many bright colors improves operator response or causes distraction? Commit to your answer.

Concept: Learn how to use colors and symbols consistently to convey meaning without confusion.

Use colors like red for alarms, green for normal, yellow for warnings. Symbols should be standard and simple. Avoid too many colors or flashy effects that distract or confuse.

Result

Operators can quickly interpret screen status by color and symbol cues.

Consistent visual language speeds recognition and reduces errors under pressure.

5

Intermediate

Designing for Readability and Accessibility

Concept: Learn how to make text and controls easy to read and use for all operators.

Use large enough fonts, clear typefaces, and good contrast between text and background. Avoid clutter and overlapping elements. Consider color blindness and lighting conditions in the control room.

Result

Screens are usable by all operators in various conditions.

Accessibility ensures no operator is disadvantaged, improving overall safety and efficiency.

6

Advanced

Dynamic Content and Context Awareness

🤔Before reading on: do you think showing all data all the time helps operators or overwhelms them? Commit to your answer.

Concept: Learn how to show only relevant information based on current process state or user role.

Use dynamic screens that highlight active alarms, hide irrelevant controls, or change layout based on process mode. This reduces clutter and focuses attention where needed.

Result

Operators see a tailored interface that adapts to current needs.

Context-aware design prevents information overload and supports faster decision-making.

7

Expert

Balancing Automation and Manual Control

🤔Before reading on: do you think fully automated screens with minimal operator input are always better? Commit to your answer.

Concept: Understand how to design layouts that support both automated monitoring and manual intervention safely.

While automation reduces operator workload, screens must still allow quick manual control when needed. Layouts should clearly separate automated status from manual controls and provide easy override options.

Result

Screens support safe collaboration between human and machine.

Knowing when and how to involve operators prevents over-reliance on automation and improves system resilience.

Under the Hood

HMI screens are built on software that reads real-time data from industrial devices and displays it visually. The layout engine arranges graphical elements based on design rules and user interactions. Behind the scenes, data tags update values continuously, triggering visual changes like color shifts or alarms. The system also manages user inputs, sending commands back to machines securely and reliably.

Why designed this way?

HMI layouts evolved to reduce operator errors and fatigue by applying human factors research. Early systems were text-heavy and confusing, causing accidents. Designers adopted visual hierarchy, grouping, and color coding to align with how humans perceive and process information quickly. The tradeoff was balancing detail with simplicity to avoid overwhelming users.

┌───────────────┐       ┌───────────────┐
│  Data Source  │──────▶│  HMI Software │
└───────────────┘       └──────┬────────┘
                                │
                 ┌──────────────┴─────────────┐
                 │   Layout Engine & Renderer  │
                 └──────────────┬─────────────┘
                                │
                   ┌────────────┴────────────┐
                   │  Visual Display & Input  │
                   └──────────────────────────┘

Myth Busters - 4 Common Misconceptions

Quick: Do you think more colors on an HMI screen always improve operator understanding? Commit to yes or no.

Common Belief: Using many bright colors makes the screen easier to understand because everything stands out.

Reality: Too many colors cause confusion and distraction, making it harder to focus on critical information.

Why it matters: Overuse of colors can delay operator response and increase mistakes during emergencies.

Quick: Do you think showing all data all the time helps operators make better decisions? Commit to yes or no.

Common Belief: Displaying every piece of data on the screen ensures operators never miss anything important.

Reality: Showing all data overloads the operator, causing important alerts to be missed among clutter.

Why it matters: Information overload leads to slower reactions and higher risk of accidents.

Quick: Do you think automation means operators don’t need to interact with the HMI much? Commit to yes or no.

Common Belief: Fully automated systems mean operators can ignore the HMI most of the time.

Reality: Operators must always be able to intervene manually; automation can fail or need adjustments.

Why it matters: Ignoring manual controls can cause delays or unsafe conditions if automation malfunctions.

Quick: Do you think bigger fonts always improve readability regardless of screen size? Commit to yes or no.

Common Belief: Making all text very large makes it easier to read on any screen.

Reality: Too large fonts reduce space for other info and can clutter the screen, hurting overall clarity.

Why it matters: Poor font sizing can force operators to scroll or miss grouped information.

Expert Zone

1

Experienced designers know that the 'golden zone'—the screen area where eyes naturally focus—should hold the most critical info, but this varies by culture and user habits.

2

Subtle use of animation can draw attention to alarms without causing distraction, but overuse leads to operator fatigue.

3

Expert layouts consider shift changes and different operator roles by providing customizable views that maintain core principles but adapt to user needs.

When NOT to use

Rigid, one-size-fits-all layouts are not suitable for complex or variable processes. In such cases, adaptive or role-based interfaces are better. Also, purely graphical layouts without textual backup can confuse new operators; a hybrid approach is preferred.

Production Patterns

In real plants, HMI screens often use layered navigation: overview screens show big-picture status, with drill-down screens for detailed control. Alarm banners persist at the top, and critical controls are placed consistently across screens. Operators receive training on screen logic to reduce errors.

Connections

User Experience (UX) Design

HMI layout principles build on UX design concepts like visual hierarchy and accessibility.

Understanding UX helps create HMIs that are intuitive and reduce operator errors, bridging industrial control and consumer software design.

Cognitive Load Theory

HMI design applies cognitive load theory by minimizing unnecessary information to avoid overwhelming users.

Knowing how the brain processes information guides layout choices that improve operator focus and decision-making.

Air Traffic Control Interfaces

Both require real-time monitoring of critical data with clear alerts and controls under high pressure.

Studying air traffic control interfaces reveals advanced strategies for alarm management and situational awareness applicable to HMI design.

Common Pitfalls

#1 Cluttering the screen with too many controls and data points.

Wrong approach:

Display all sensor readings, controls, and logs on a single screen without grouping or prioritization.

Correct approach:

Organize information into logical groups and use multiple screens or tabs to separate details from overview.

Root cause:

Misunderstanding that more information equals better control, ignoring human attention limits.

#2 Using inconsistent colors and symbols across screens.

Wrong approach:

Red means alarm on one screen, but on another screen red is used for normal status.

Correct approach:

Define and apply a consistent color and symbol standard throughout all screens.

Root cause:

Lack of a design guideline or style guide for the HMI project.

#3 Ignoring accessibility needs like font size and contrast.

Wrong approach:

Using small fonts with low contrast colors that are hard to read in bright control rooms.

Correct approach:

Use large, clear fonts and high contrast colors tested under real lighting conditions.

Root cause:

Assuming all operators have perfect vision and ideal viewing environments.

Key Takeaways

HMI screen layout principles ensure operators can quickly find and understand critical information to control industrial processes safely.

Good layouts use visual hierarchy, grouping, consistent colors, and accessibility to reduce errors and improve efficiency.

Dynamic and context-aware screens prevent information overload by showing only relevant data based on process state.

Balancing automation with manual control in layouts supports safe human-machine collaboration.

Ignoring these principles leads to cluttered, confusing screens that increase risk and slow operator response.