The Importance of HMI Design for PLC and DCS Systems

Key Takeaways:

1. Clarity Over Clutter: High-performance HMI design gives operators only the information they need, exactly when they need it.

2. Colour with Purpose: Grey-based screens reserve colour for true abnormalities, boosting reaction speed.

3. Actionable Insights: Data is presented as trends, indicators and context—not overwhelming raw numbers.

4. Smart Alarms: Rationalized alarms cut through the noise so operators focus on critical issues.

5. Operator-Centric Design: iPAC Automation builds HMIs that improve safety, reduce downtime, and enhance control efficiency.

Do you remember the first time you saw a TV remote with 80 tiny, identical buttons? Or tried to navigate a website where every piece of information was presented with the same screaming-red urgency? It’s confusing, frustrating and ultimately, ineffective.

Now, imagine that same level of confusion, but instead of just missing your favourite TV show, a wrong button press could lead to a multi-million dollar production batch being ruined, an environmental incident, or a serious safety hazard.

Welcome to the world of the plant operator. Their “remote control” is the Human-Machine Interface (HMI), the primary window into the complex processes run by PLCs (Programmable Logic Controllers) and DCS (Distributed Control Systems). For decades, the philosophy behind HMI design was simple: show as much data as possible. Screens were cluttered with colourful pipes, spinning animations and arrays of numerical values.

The result? Operators were overwhelmed with data but starved of actual information. This is why the industry is undergoing a radical shift away from decorative, cluttered screens towards High-Performance HMI design. It’s a philosophy that recognizes the HMI is not just a data dump; it’s a critical tool for decision-making.

From Cluttered to Clear: The High-Performance Philosophy

The core idea behind high-performance HMI design is simple: provide the operator with the information they need to make the right decision, as quickly as possible.

It’s about maximizing situational awareness. When an operator glances at a screen, they should be able to answer three questions in under five seconds:

1. Is the process running normally?
2. If not, what is the problem?
3. What is the priority of the problem?

Traditional HMIs often fail this simple test. A screen filled with bright green pipes and numbers doesn’t tell you if things are “good.” It just tells you they’re “on.” A high-performance HMI, by contrast, uses design techniques to make the abnormal stand out.

Key Principles of High-Performance HMI Design

Building an effective HMI is both an art and a science, grounded in an understanding of human psychology and attention. Here are the pillars of the modern approach.

1. Grey is the New Good

This is perhaps the most striking difference. In a high-performance HMI, the background and normal-state equipment are presented in muted shades of grey. Why? Because when everything is quiet and calm, the operator’s attention isn’t drawn to anything in particular.

This makes the use of colour far more effective. Colours like red, yellow and orange are reserved exclusively for abnormal situations and alarms. When a colour does appear on the screen, it acts as a powerful visual cue that immediately draws the operator’s eye to the problem.

2. Data, Presented as Information

Drowning an operator in raw data is counterproductive. A number like “251.79 RPM” is less useful than seeing that value presented on an analog trend indicator that clearly shows it’s within its normal operating range.

High-performance HMIs favour graphical representation of data over raw numbers. They use:

• Analog indicators and trends: To show not just the current value, but where it is relative to its normal range and how it’s behaving over time.
• Embedded charts: To show key relationships between variables directly on the process graphic.
• Minimalism: Only the data needed for the operator to make a decision is shown on the main screen. Detailed information is available but requires the operator to intentionally drill down.

3. A Smarter Alarm Philosophy

One of the biggest problems in traditional control rooms is “alarm flooding.” An operator is bombarded with hundreds of alarms, most of them low-priority or nuisance alarms, making it impossible to identify the truly critical ones.

A high-performance HMI is built on a foundation of alarm management and rationalization. This is a systematic process to ensure that every alarm is:

• Actionable: The operator knows what to do in response.
• Unique: It doesn’t duplicate another alarm.
• Consequential: It indicates a real problem that could lead to a negative outcome.
• Prioritized: The alarm’s colour, shape and sound clearly indicate its urgency.

By filtering out the noise, we ensure that when an alarm does occur, the operator takes it seriously.

4. Intuitive Navigation

A plant is a complex system. An operator needs to be able to move from a high-level overview of the entire plant down to the details of a single control loop in just a few clicks. The HMI’s navigation structure should be logical and consistent, mirroring the physical layout or process flow of the plant. This reduces the cognitive load on the operator and allows them to find what they need without having to think about it.

The iPAC Automation Advantage: Design with Purpose

An HMI is the face of your automation system. A powerful, well-programmed PLC or DCS can be crippled by a poorly designed interface that leads to operator error and slow response times.

At iPAC Automation, we believe that HMI development is not just a programming task; it’s a dedicated design process. It requires collaboration with the people who will use it every day-the operators. We focus on:

• Understanding the process and the operator’s tasks.
• Applying ISA-101.01 HMI design standards and best practices.
• Implementing a robust alarm management strategy.
• Creating screens that are clean, intuitive and, above all, effective.

Ultimately, a great HMI doesn’t just look better; it performs better. It leads to faster troubleshooting, reduced downtime, fewer mistakes and a safer operating environment. It transforms the control room from a place of reactive firefighting to one of proactive, informed control.

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