Essential Guide to Human-Machine Interfaces

Wondering how human operators effectively control and interact with machines? HMI, or Human-Machine Interface, is the answer. At its core, HMI bridges the gap between complex machinery and human oversight, allowing for streamlined operation and control. From monitoring processes to adjusting settings and intervening manually, HMIs serve as crucial tools across numerous industries.

This guide dives into how HMIs function, their evolution, their key components, and their applications, equipping you with the insights needed to leverage this technology.

Key Takeaways

  • Human-Machine Interface (HMI) technology enables human operators to interact with machines through a combination of software and hardware, optimizing user experience and industrial control processes.
  • HMI has significantly evolved from early computing interfaces to sophisticated touchscreens and mobile devices, fostering increased productivity and operational efficiency across various industries.
  • Effective HMI design prioritizes user requirements, integrates seamlessly with SCADA systems for broader industrial control, and continues to advance with innovations in AI, AR/VR, and remote monitoring capabilities.

Understanding HMI: A Definition

Image showing HMI at operator HMI station

HMI, or Human-Machine Interface at its simplest, is a fusion of software and hardware that enables human operators to interact with machines. Think of it as a sophisticated dashboard, or an HMI screen, enabling operators to monitor processes, adjust settings, and even manually override automated operations.

A high performance HMI can present itself in various forms: standalone terminals, integrated dashboards, or even mobile devices. Its role is to visualize data about operations and control machinery, thus enhancing the user experience and optimizing the process.

However, HMI extends beyond being a high-tech control panel. It lets operators connect directly with complex machinery, tweaking processes to enhance performance. While HMI systems incorporate graphical user interfaces (GUIs) for visual representation, they are distinct concepts with specialized functionalities in industrial contexts.

The primary role of an HMI in industrial automation is to serve as an operator control panel, providing graphical representations of automated systems and enabling convenient manual interventions when necessary.

The Evolution of HMI Technology

Evolution of HMI technology

The evolution of HMI technology bears witness to the remarkable advancements in human-machine interfaces. In the early days of computing, interaction was carried out using punch cards, which did not provide real-time interaction and often required hours to produce output. As technology advanced, computers with simple interfaces included keyboards and a line of text on a screen, evolving to include keyboards and displays with basic graphics by the early 1980s.

The invention of the computer mouse and graphical user interface in the 1980s revolutionized HMI by facilitating navigation and command input. Fast forward to the 1990s, and graphical workstations equipped with mice and keyboards became the standard in technology sectors. The late 1990s introduced us to touchscreens, necessitating UI design to accommodate interactivity on smaller screens, with PDAs and early mobile devices leading the change.

The advent of iPhone and Android devices in the late 2000s, featuring user-friendly touch interfaces, significantly raised expectations for mobile data accessibility. These significant advancements in HMIs continue to improve digital device operation, yielding increased productivity and less waste and errors in project execution.

Looking ahead, HMI technology is evolving towards minimized physical interaction, with forecasts suggesting a shift towards hands-free operation as a norm, incorporating automatic control operations.

Key Components of an HMI System

Grasping the key components of an HMI system is vital for unlocking its maximum potential. One of the primary components is the programmable logic controller (PLC). HMIs with integrated PLCs, known as HMI/PLC combo units, are utilized for efficient monitoring and control, thereby eliminating the need for separate communications wiring. To effectively operate a PLC using an HMI, it is crucial to have knowledge of all the PLC registers.

Another vital aspect of modern HMI systems is the incorporation of touch screens and various interfaces, such as:

  • screens
  • buttons
  • levers
  • computer mice
  • keyboards

for interaction. Communication protocols like Modbus TCP/IP, EtherNet/IP, and Profinet are integral to HMI systems, providing the means for connectivity between various HMIs and multiple PLCs from different suppliers via an Ethernet network. Wiring an HMI into a system commonly involves using connection methods such as USB, RS-232, or RS-485 cables between the HMI and the PLC.

Lastly, basic HMIs enable operators to monitor key parameters such as:

  • temperature
  • processing counts
  • machine status
  • material numbers

These parameters are essential for an effective control process and to modify control settings as needed.

Embedded HMIs, which employ an embedded operating system, offer optimization for HMI software hosting and are generally more cost-effective and durable than PC-based HMIs.

HMI in Various Industries

HMI in various industries

Various industries have embraced HMI technology, each capitalizing on its capabilities to streamline operations. In the manufacturing industry, HMIs facilitate machine and process control by connecting machines, sensors, and actuators to systems like I/O and PLC applications.

These manufacturing HMIs assist operators in optimizing efficiency by providing data for staff reallocation and machine setting adjustments to improve performance. Industrial HMIs in manufacturing may vary from stand-alone terminals for individual machines to components of a distributed system in complex applications.

The healthcare industry also leverages HMIs for critical medical devices including patient monitoring systems, IV pumps, and various equipment controls. HMIs in healthcare are designed to enhance both operator and patient experience, emphasizing reliability in critical applications.

However, the application of HMI is not limited to manufacturing and healthcare. It has a wide-ranging impact, optimizing industrial processes in industries including:

  • Energy
  • Food and beverage
  • Oil and gas
  • Power
  • Recycling
  • Transportation
  • Water and wastewater

More industries, such as food processing, pharmaceutical manufacturing, SCADA systems, robotics, and transportation, continue to expand the spectrum of HMI usage.

Designing Effective HMI Solutions


Designing effective HMI solutions

Crafting effective HMI solutions is an art form that strikes a balance between user requirements and technical abilities. Good interface design enables operators to accomplish their duties efficiently and effectively with minimal errors, following established design standards and conventions to enhance usability and reduce confusion.

Effective HMI design matches the operator’s mental model, providing contextually relevant information and clear zones for information and controls, making it intuitive and minimizing the cognitive load.

HMI solutions improve accessibility by prioritizing usability for diverse users and minimizing user errors, with a focus on:

  • Safety and error prevention, especially in high-stakes environments
  • Providing timely feedback and guidance via the HMI interface
  • Informing users about system status, outcomes, and possible next actions
  • Fostering understanding and a sense of control
  • Allowing for iterative testing and improvements

The visual design of an HMI should support operational efficiency with a coordinated information design, employing principles like alignment and balance to enhance interaction and the operator’s perception of the system.

Industrial HMI design involves balancing functional requirements with operator usability, drawing inspiration from consumer electronics interfaces such as touch screens for familiarity and ease of use.

HMI and SCADA: Complementary Technologies

In the world of industrial automation, HMI and SCADA systems go hand in hand. A Human-Machine Interface (HMI) is a hardware device that runs software allowing humans to interact with machines, while a Supervisory Control and Data Acquisition (SCADA) system includes both hardware and software components for controlling and monitoring industrial processes.

SCADA systems can operate without an HMI, but including an HMI is beneficial as it allows operators to better understand and communicate with the system, as well as receive notices about errors that may arise.

While HMI is a component of the SCADA system, allowing for user interaction and visualization, SCADA encompasses a broader scope of functionalities including data acquisition, control, and monitoring of the entire industrial process.

In industrial automation, HMIs are crucial for delivering information to the operator, while PLC systems detect issues within the SCADA system and relay that information to the HMI for the operator to address.

SCADA systems are regarded as the central database for storing and controlling operations on a large scale, whereas HMIs and PLCs are the interfaces and controllers that interact with this central system, respectively. The HMI component within the SCADA-PLC framework can take various forms, such as screens or keyboards, facilitating human interaction with the overall larger industrial control system for process control and monitoring.

HMIs allow for the digitization and centralization of data for a viewer, making important information available in graphs, charts, or digital dashboards, and connecting with SCADA, ERP, and MES systems.

Remote Monitoring and Mobile HMI

The emergence of remote monitoring and mobile HMI solutions has transformed our interaction with machines. Touch screens and mobile devices have revolutionized HMI technology, allowing operators to interact with machine controls through intuitive tapping or touching, enabling remote monitoring functionality.

Data and visualizations from field devices can be accessed through edge-of-network HMIs, with an increasing trend towards sending data to the cloud for remote analysis and access.

Cloud-based HMI solutions provide a platform for managing IIoT data, connecting operational technology to informational resources while prioritizing data security. Remote monitoring systems ensure secure operations by utilizing cloud-capable routers and solutions with comprehensive information security management systems, along with encrypted communications.

Centralized monitoring and regular security scanning by independent third parties are essential components of a robust remote monitoring system.

To support performance and redundancy needs, cloud-based HMI solutions utilize networks of globally distributed servers housed in certified data centers. The advent of these technologies has increased flexibility and accessibility, allowing operators to access data and controls from anywhere, anytime.

The Future of HMI: Emerging Trends and Innovations


Future trends in HMI technology

HMI technology’s future is filled with thrilling prospects. High-performance HMIs are being developed to enable faster and more effective interaction by selectively presenting the most necessary or critical information using thoughtfully applied design elements.

Emerging technologies like AR, VR, and MR are poised to revolutionize HMI by enhancing the visualization of manufacturing functions and offering immersive user experiences.

The integration of AI into HMI systems is expected to significantly enhance decision-making capabilities, provide context-aware interactions, and establish a more intuitive user interface.

Advancements in interaction technologies, including gesture-based interfaces, voice-activated systems with natural language processing, and brain-computer interfaces, are paving the way for a more immersive and intuitive HMI experience.

Next-generation HMIs are being designed with flexibility and scalability in mind, featuring modular components and adaptable software frameworks to ensure longevity and adapt to organizational change. These emerging trends and innovations are paving the way for more immersive and intuitive user experiences, transforming the landscape of human-machine interaction.

Selecting the Right HMI Software and Hardware

Selecting the appropriate HMI software and hardware is a pivotal step towards guaranteeing optimal system performance. When choosing HMI programming software, consider the following factors:

  • User-friendly graphics
  • Efficient development tools
  • Supported operating systems (Windows, Android, or Linux)
  • Data logging capabilities
  • Remote connectivity features
  • Security protocols

These factors are fundamental for compatibility and functionality.

Regarding the selection of HMI hardware, it should be based on:

  • Processor performance suitable for expected graphics and tag counts
  • Physical size adjusted for user preference and space constraints
  • Presence of environmental protections for temperature extremes and potential exposure to water or chemicals
  • Connectivity options such as Ethernet, serial, USB, and HDMI for communication with PLCs and other devices

Consideration of these factors is crucial when choosing HMI hardware.

Furthermore, it is essential to ensure that the HMI supports modern communication protocols for stable data transmission.

Before adopting an HMI system on a large scale, it is advisable to obtain a test sample of the HMI hardware and software to verify system compatibility and performance. This allows for a comprehensive understanding of the system’s capabilities and limitations, ensuring that it aligns with your specific needs and expectations.

HMI Troubleshooting and Maintenance

Troubleshooting and maintaining HMI is critical for optimizing system performance and durability. Incorporating careful design in HMI to include extra layers of protection for critical functions, plain language error messages, and clear instructions can assist in error prevention and aid in recovery.

When it comes to diagnosing wiring problems, using a voltmeter for continuity checks on HMI cables can help identify issues, while swapping the communication cable can diagnose issues with HMI-PLC communication.

In case of challenges, instructional videos can serve as a valuable resource for HMI troubleshooting. These videos provide step-by-step guides on how to resolve common issues, making it easier for operators to fix problems without needing extensive technical knowledge.

When more complex issues arise, it’s always a good idea to contact applications engineers for professional assistance. Their expertise and experience can help resolve issues quickly and efficiently, minimizing downtime and ensuring your HMI system continues to operate smoothly.


In summary, Human-Machine Interface (HMI) technology is a crucial component in the landscape of industrial automation and beyond. From an interface for operators to monitor and control machinery, to a tool for optimizing industrial processes across various industries, HMI plays a pivotal role.

The evolution of HMI technology, from simple text-based interfaces to high-performance HMIs, is a testament to the progress in this field. As we look to the future, emerging trends such as AR/VR/MR integration, AI-enhanced decision-making, and advanced interaction technologies present exciting possibilities.

Selecting the right HMI software and hardware, and ensuring effective troubleshooting and maintenance, are critical for optimal system performance. As we continue to explore and innovate, the potential of HMI technology seems limitless.

Frequently Asked Questions

What is a PLC and HMI?

A PLC (Programmable Logic Controller) is used to control equipment in a process, while HMI (Human Machine Interface) products allow process personnel to interact with the PLC control system.

What is an example of a HMI?

Some examples of Human Machine Interface (HMI) devices are touchscreens and keyboards, which we encounter in our daily lives. These devices enable humans to engage and interact with machines.

What is difference between HMI and SCADA?

The main difference between HMI and SCADA is that HMIs are subsets or components of a SCADA system. Additionally, a DCS or Distributed Control System is very similar to a SCADA system, and may also use one or more HMIs.

What is the difference between HMI and GUI?

In summary, the main difference between HMI and GUI is that HMI is a control system for human operators to control machinery, while GUI is a digitally created interface used to control electronic devices.

How has HMI technology evolved?

HMI technology has evolved from early punch cards to modern graphical user interfaces, touchscreens, and mobile devices, with continuous advancements focused on enhancing user experience and productivity.