Choosing the right Human Machine Interface (HMI) display for an industrial system isn’t just about picking the latest model or the largest screen. It’s about understanding the full scope of your application—from environmental challenges to software compatibility—and making sure the HMI you choose fits the specific needs of your system. If you’ve been tasked with sourcing components for a new automation setup, here’s a practical guide to help you select the best HMI for the job.
1. Start by Understanding the System
Before comparing models, gather the essential details of your application. Ask yourself:
- What certifications or physical ratings are required for components in this system?
- What regulatory or compliance standards must be met?
- What kind of environmental challenges will the equipment face?
- What other devices are present, and what are their communication needs?
- What software capabilities are necessary to build the application?
This information forms the foundation for identifying an HMI that will not only function in the environment but also meet the broader technical and compliance requirements.
2. Consider Protection Ratings and Certifications
Environments dictate equipment. An HMI suitable for a clean office space might fail in an industrial setting where equipment is washed down with high-pressure water or exposed to volatile chemicals.
- IP Ratings (Ingress Protection): For washdown environments, look for IP66 or higher to ensure the HMI enclosure can resist water and dust intrusion.
- Hazardous Location Ratings (C1D2, ATEX, etc.): In environments with explosive gases or vapors, HMIs must have certifications like Class 1 Division 2 to ensure that internal circuitry and housing won’t ignite the atmosphere.
These certifications are not optional in critical environments—they are mandatory for safety and compliance.
3. Account for Real-World Environmental Hazards
Beyond certifications, consider how the HMI will hold up physically over time. Will it be:
- In contact with sharp tools or moving equipment?
- Exposed to caustic or acidic substances?
- Subjected to extreme temperatures or UV exposure?
Choosing an HMI with the right enclosure material and construction (e.g., stainless steel, anti-corrosive coating) is vital to long-term reliability.
4. Don’t Overlook Industry-Specific or Non-Critical Certifications
Some certifications may not relate directly to physical safety but are crucial for regulatory or IT security reasons:
- FDA 21 CFR Part 11: Needed in pharmaceutical or food industries to ensure electronic records and signatures are handled correctly.
- IEC 62443-4-1: A cybersecurity development lifecycle standard that shows the vendor follows secure software design practices.
Understanding these requirements ensures the HMI will be accepted during audits and protect the integrity of your system’s data.
5. Evaluate Communication Compatibility and Flexibility
An HMI should be a seamless bridge between the user and the machinery. If it can’t communicate with the system’s devices, you’ll run into costly integration headaches.
- Check for Protocol Support: Does the HMI natively support protocols used by your devices (EtherNet/IP, Modbus, OPC UA, etc.)?
- Verify Hardware Interfaces: Are the right physical ports available (serial, Ethernet, USB)?
- Consider Future Needs: Will the HMI support expansions or new device types later on?
If the HMI can’t communicate directly, will you need a protocol gateway—or should you consider a different product entirely?
6. Evaluate the HMI Software Platform
A great HMI display is only as good as the software platform that powers it.
- Start with basic features: Can you create the visual layouts, tag structures, alarms, and data logging you need?
- Dive into advanced tools: Does the platform support scripting, remote access, IIoT, or database integrations?
- Get expert input: Talk with an engineer from the vendor to assess whether your specific project requirements can be accomplished using their software.
Often, what looks like a fit on paper may have limitations—so ask questions early.
7. Choose the Right Display Size and Touch Type
Finally, consider the physical interface—the part your operators will see and touch every day.
- Screen Size and Resolution: Larger screens can display more data but may be unnecessary in tight enclosures. Higher resolution improves clarity, especially with detailed graphics or trends.
- Touchscreen Type:
- Resistive touch: Works with gloved hands and styluses. Ideal for harsh or dirty environments.
- Capacitive touch: Supports multitouch gestures and smoother navigation but usually requires bare fingers or special gloves.
You’ll also want to make sure the UI design fits the screen—cramped buttons and crowded data can lead to accidental touches and operational issues.
Final Thoughts
Selecting the best HMI display is a balancing act between environmental durability, compliance, communication capability, and usability. By understanding your application’s specific requirements upfront and asking the right questions, you can choose an HMI that not only survives in the field—but thrives. Whether you’re building a new control system or upgrading an old one, taking a methodical approach to HMI selection can save you time, money, and rework down the line.