Walk into most manufacturing plants and you'll find HMI screens that look like someone tried to put every piece of information on one display. Bright colors everywhere. Numbers flickering faster than a human can read them. Alarms queuing up in a banner that operators have learned to ignore.
The screen looks busy. The operator looks calm. That's not because nothing is happening — it's because the interface has become noise, and the operator is working around it rather than with it.
HMI design is not just a graphics exercise. It's an engineering discipline that directly affects how quickly operators can detect abnormal conditions, diagnose problems, and take action. Good design saves time. Poor design costs production.
The Problem With Most Legacy HMI Screens
Legacy HMI design — and many modern systems built to the same habits — tends to share several characteristics that make them less useful than they should be:
- Overly colorful: Every pipe is a different color. Every state has a bright indicator. The result is screens that are visually overwhelming and don't communicate priority.
- Mimicking the P&ID: Screens are laid out to match the physical plant drawing, not to support the cognitive task of process monitoring.
- Static alarm limits: Setpoints are fixed regardless of operating mode or batch state, generating nuisance alarms that train operators to ignore the alarm system.
- No context for values: A temperature reading of 347°F means nothing without knowing the setpoint, the normal range, and the direction of trend.
- Navigation that requires memory: Operators learn the screen sequence by repetition, not because the navigation is intuitive.
The ASM Consortium, an industry research group focused on operator performance, has documented that ineffective alarm management and poor HMI design are contributing factors in the majority of major industrial incidents. The console operator's ability to detect, diagnose, and respond to abnormal situations depends directly on the quality of the interface they're working with.
High-Performance HMI: The Design Philosophy
High-Performance HMI (sometimes called Level 4 or HP-HMI) is a design methodology developed specifically to address the shortcomings of traditional HMI design. Its core principles are:
1. Grayscale Base with Purposeful Color
High-performance HMI screens use a neutral gray background with grayscale graphics as the default state. Color is reserved for deviation from normal: yellow for off-normal, red for critical. When everything is colorful, nothing stands out. When everything is gray, the red indicator draws the eye immediately.
This principle feels counterintuitive to operators used to bright screens — and for the first few days of exposure, they often miss the old look. Within a week, the advantage is usually clear.
2. Context for Every Value
Every displayed value should have enough context that an operator can immediately assess its status: the current value, the setpoint or target, the normal operating range, and an indication of trend direction. A bar graph with a highlighted normal range communicates more than a number alone.
Some implementations use analog-style meters or trend sparklines inline with the current value. The goal is to answer the operator's implicit question — “is this OK right now?” — without requiring them to mentally compare a number to a remembered limit.
3. Process Visualization at the Right Level of Abstraction
Screens should support the task, not replicate the P&ID. An overview screen should show the whole process state at a glance — not every valve and transmitter, but the key indicators that tell an operator whether the process is healthy. Detail screens exist for diagnosis.
The navigation hierarchy matters: operators should be able to move from overview to area to unit to detail intuitively, and always know where they are and how to get back.
4. Alarm Management
An alarm system that generates more than one or two alarms per operator per day is a system that needs rationalization. When operators are processing 100 alarms per shift, the critical ones get lost in the noise.
Effective alarm management requires defining which conditions actually require operator action — and setting limits accordingly. Dynamic alarm limits that adjust based on process state, alarm suppression during startup and shutdown modes, and alarm prioritization by consequence are all tools for reducing alarm flood.
5. Consistency
Once design standards are established, they should be applied uniformly across every screen. Operators should be able to navigate any screen in the system using the same mental model — same colors, same symbols, same navigation patterns. Inconsistency forces operators to context-switch and increases cognitive load at exactly the moments when cognitive load is highest.
Practical Implementation
Applying these principles to a new system is straightforward if they're built into the design specification from the start. Retrofitting them to an existing system is harder but still achievable:
- Develop a design standard document before starting any screen development — colors, symbols, navigation conventions, alarm priorities, units of measure
- Start with the overview screen: if you can't fit the key process indicators on one screen at a level of abstraction that's useful, the design needs work
- Audit your alarm database: identify the top 10 most frequently occurring alarms and resolve each one — rationalize the limit, change the process, or suppress the nuisance alarm
- Conduct usability reviews with operators during development — not just at the end. Operators who work with the system daily have invaluable insight into what information they actually need
- Document your standards and enforce them through design reviews
This is the kind of standards work we build into every SCADA & HMI development project, rather than treating screen design as an afterthought.
What Platform You're On Matters Less Than You Think
High-performance HMI principles can be applied on virtually any modern platform — Ignition, FactoryTalk View, WinCC, Wonderware. The methodology is platform-agnostic. What matters is having a design standard and applying it consistently.
That said, some platforms make it easier than others to enforce standards across projects. Ignition's templating system, for example, allows symbol libraries and design standards to be enforced at the component level — making it harder for individual screens to deviate from the standard.
The Bottom Line
HMI design is not decoration. It's the interface between your control system and the human being responsible for running your plant. Screens that communicate process state clearly, prioritize critical information, and support operator decision-making are the difference between catching an abnormal condition in 10 seconds and missing it for 10 minutes.
Good HMI design doesn't cost more than poor HMI design. It just requires starting with the right principles — and applying them consistently.
Logic Control Systems develops SCADA and HMI applications using Ignition Certified integrator practices, with high-performance HMI design built into every project. If you're building a new system or modernizing an existing one, contact us at 817-757-9507 or [email protected].