Editor’s Note: This blog post (originally published in September 2024) has been updated for accuracy and comprehensiveness.
What started as a simple replacement for buttons and dials has evolved into one of the most powerful tools in modern manufacturing: the Human-Machine Interface (HMI).
More than just a screen, an HMI is the bridge between operators and complex industrial systems. It delivers real-time monitoring, intuitive control, and instant access to critical process data, all from a single point of interaction.
Whether you’re a small manufacturer searching for an affordable touchscreen panel or a plant engineer weighing a web-based interface against a traditional unit, understanding how HMIs work is essential to choosing the right one and getting the most from your equipment.
Let’s get into it.
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An HMI works by gathering data from industrial controllers, such as Programmable Logic Controllers (PLCs), and converting it into visual, interactive screens that operators can use to monitor and control equipment in real time. Through touch or physical input, operators send commands back to the machine, creating a continuous feedback loop.
In this role, the HMI serves as the central interface between humans and machines, delivering real-time process visibility, enabling on-the-fly adjustments, and ensuring operators can respond quickly to changing conditions.
It's important to distinguish an HMI from an Industrial PC (IPC). While an IPC can function as an HMI, the reverse is not always true. An IPC is a versatile general-purpose computer used for multiple applications, whereas an HMI is specifically engineered and optimized for industrial control and process monitoring.
At the core of every HMI system lies a sophisticated graphical user interface (GUI) that enables operators to communicate effectively with PLCs. Touchscreen HMI panels make operations intuitive by allowing direct interaction through simple touch gestures. From a single interface, operators can:
As HMIs continue to evolve, it’s important to understand how they differ from and work alongside SCADA (Supervisory Control and Data Acquisition) systems. Although the terms are often used together, they serve different roles in industrial automation.
| System | Primary Role |
|---|---|
| HMI (Human-Machine Interface) | Local machine interface for real-time control and operator interaction |
| SCADA (Supervisory Control and Data Acquisition) | Plant-wide or enterprise-level monitoring, data collection, and historical analysis |
An HMI allows operators to control a specific machine or production line, visualize live data, acknowledge alarms, and make adjustments. SCADA operates on a broader scale, collecting data from multiple HMIs and PLCs to provide centralized visibility, reporting, and remote access across an entire facility or multiple sites.
Together, HMIs and SCADA systems enable smarter manufacturing by supporting:
If your focus is machine-level control, an HMI alone may be sufficient. If you require system-level oversight, multi-site visibility, or long-term data analysis, SCADA becomes a critical layer.
Tip: Modern web-based HMIs are increasingly bridging the gap by offering SCADA-like visualization capabilities, especially in IIoT and cloud-connected environments.
HMI effectiveness depends on proper customization. System designers configure custom displays, set alarm thresholds, define user access levels, and tailor the interface to specific operational requirements. This customized setup, combined with robust HMI-PLC connectivity, ensures operators can monitor multiple processes simultaneously and make informed decisions swiftly, driving faster response times and improved operational outcomes.
| Need help selecting or configuring an HMI? Our team of specialists works with manufacturers of all sizes. If you need guidance or a second opinion, our experts are here to help. Just reach out. |
The evolution of Human-Machine Interfaces reflects how industry itself has evolved. Early HMIs were nothing more than panels of buttons, switches, and indicator lights, functional but limited and prone to operator error. As computing advanced, command-line interfaces and basic batch systems emerged, demanding technical knowledge to operate even simple equipment.
The introduction of GUIs marked a major turning point. Touchscreens replaced mechanical panels, giving operators real-time visibility, alarms, and control from a single display. This shift made HMIs more intuitive and significantly improved efficiency on the factory floor.
But HMI evolution isn’t stopping at the touchscreen.
We are now entering a new era where interfaces are becoming adaptive, intelligent, and increasingly invisible. Future HMIs will:
The HMI is no longer just a panel; it is becoming a flexible, context-aware assistant built to enhance human capability. Learn more about the evolution of HMIs and future trends and predictions in our blog post, Human Machine Interfaces (HMIs): Trends and Future Directions.
Human-Machine Interfaces come in several forms, each designed to support different operational needs. Traditionally, HMIs evolved through three core categories:
Today, HMIs are far more versatile and customizable, available in multiple mounting styles — panel-mounted, rack-mounted, portable, and embedded — making them adaptable across industries like manufacturing, automotive, energy, and healthcare. Modern systems support multi-touch controls, real-time data visualization, alarms, and even remote access.
As technology advances, two primary form factors dominate most industrial applications: Touch Panels and Web Panels. Understanding the difference is key to selecting the right interface.
Touch panels are the standard in factory automation. They store and run the HMI program locally and connect directly to PLCs using common protocols like Ethernet/IP, Profinet, and Modbus TCP. Brands such as Rockwell, Siemens, and Schneider integrate seamlessly with these devices. Once configured, the touch panel communicates continuously with the PLC to visualize processes, manage alarms, and enable direct operator control.
Ideal for:
Web panels don’t store visualization locally. Instead, they display HMI screens hosted on a web server, often inside the PLC itself. By pointing to an IP address, the panel simply renders whatever interface is served from the controller. This model is excellent for remote viewing and IIoT applications, particularly with PLCs such as Phoenix Contact models that include built-in web servers.
Ideal for:
Whether you deploy a traditional touch panel or a web-based interface, choosing an HMI that aligns with your control strategy is key to enabling smarter, safer, and more responsive operations. And if you need support along the way, our experts are here to help.
| Application Need | Best Choice |
|---|---|
| Local machine control | Touch Panel |
| Remote or multi-user access | Web Panel |
| High-performance graphics | Touch Panel |
| IIoT / Cloud connectivity | Web Panel |
Choosing an HMI isn’t just about features or cost; it’s about selecting hardware that can survive the environment it’s placed in and perform reliably over time. Before committing to an HMI panel, it’s critical to consider its durability, visibility, and suitability for the conditions on your plant floor or job site.
Industrial environments are demanding, and not every HMI is built to handle moisture, dust, vibration, or washdown conditions. Always verify the panel’s enclosure rating:
Using a non-rated consumer display in these environments can result in display failure, downtime, or safety risks.
How an HMI is installed affects both usability and longevity. Select a format appropriate for the application:
Consider cable access, serviceability, and protection from impact or operator contact.
| Display Factor | Key Considerations |
|---|---|
| Screen Size | Small (4–7") for simple machines; larger (10–15"+) for full dashboards |
| Touch Type | Resistive (glove-friendly) vs. Capacitive (multi-touch, modern gestures) |
| Visibility | High-brightness or sunlight-readable screens for outdoor or crane systems |
| Durability | Scratch-resistant glass, shock-rated display assemblies |
Basic HMIs handle buttons and alarms. Advanced models render high-resolution graphics, trends, and even handle scripting or edge computing.
Undersizing hardware can result in lag, alarm delays, or communication drops.
Bottom line: The right HMI is more than a screen; it’s a long-term asset. Selecting hardware built for your environment and conditions ensures performance, reduces downtime, and extends the life of your automation investment.
Selecting the right HMI software is just as important as selecting the hardware. The software defines how easily you can develop screens, connect to devices, and maintain the system over time. When evaluating HMI platforms, consider:
Choosing reliable software ensures long-term maintainability and scalability, especially as systems evolve with Industry 4.0 and remote connectivity.
HMIs have revolutionized the way we interact with industrial systems, providing intuitive and user-friendly solutions for monitoring and controlling complex processes. From their humble beginnings to the advanced web panels of today, HMIs have continually evolved to meet the demands of modern industry. By integrating real-time data visualization, remote monitoring, and advanced diagnostic tools, HMIs enhance productivity, reduce costs, and improve overall operational efficiency.
For help choosing the best HMI for your projects, contact your local Airline Sales Representative to keep your systems running smoothly. New to Airline? Reach out to our expert customer service team, which will connect you with an industrial automation specialist.