Human-machine interface (HMI) and operator interface (OI) devices help humans monitor and change industrial or facility processes or factory automation. They began as control panels with mechanical devices, then incorporated electrical elements, including microprocessors, and often have been replaced in form and function by computers or thin-clients, often referred to as a user interfaces (UI), OI or HMI with a touch screen or touch panels (computers with a screen that actuate on contact), keyboard, mouse or keypad or voice actuation.

HMI, OI Content

HMI/SCADA systems: Upgrade your migration

When upgrading human-machine interface (HMI) and supervisory control and data acquisition (SCADA) software, don’t just create a new version of the old. Enable workers with advanced HMI/SCADA capabilities after migration. See five tips for optimizing HMI/SCADA screens.


Learning Objectives

  • Human-machine interface (HMI) and supervisory control and data acquisition (SCADA) systems can take advantage of modern control system changes.
  • HMI and SCADA systems, when used optimally, provide a clear information flow to the user.
  • Modern systems also should take advantage of mobile flexibility so information can be accessed almost anywhere.

HMI/SCADA insights

  • Modern human-machine interface (HMI) and supervisory control and data acquisition (SCADA) systems can be modernized and migrated so they can take advantage of modern data processing and gathering techniques, which increase their potential value on the plant floor and throughout the enterprise.
  • SCADA software modernization should not come at the expense of clarity or simplicity. The fundamentals for HMI software upgrades remain true: The information from an HMI or SCADA system after migration should provide context in a way that is easy to understand so the insights can be delivered in a timely manner.

When organizations plan to upgrade software for human-machine interface (HMI) and/or supervisory control and data acquisition (SCADA), a lot of questions accompany the migration project. Where do we begin? What do we keep, and what do we toss? Which HMI screens need redesigns?

All these questions are important, but another key factor is understanding users can do much more than a simple upgrade with new SCADA and HMI software. Why not go beyond that, and take the opportunity to make changes that will provide several significant benefits for a manufacturing company or process facility?

If the company is moving from one vendor to another, there’s no “easy button” that converts everything. Even if there were, the idea isn’t as appealing in reality. If the user keeps all the same screen designs in the new system, and doesn’t use modern design principles, it’s like putting worn tires on a new car. Companies will still operate, but not nearly as well as they could.

If companies take advantage of modern HMI/SCADA design ideas and technologies, they can get more data, share more data to more places and improve the data quality. They also can provide operators with HMI/SCADA screens that are understood more quickly, resulting in faster reactions and easier training of new employees. SCADA isn’t just SCADA anymore. It can do a lot more than it could a short time ago. This is a chance for companies to get a SCADA system that goes well beyond prior capabilities to deliver results that can have a sizable impact on a facility’s operations.

Standardize the SCADA system during an upgrade

When upgrading a SCADA system, a common question is: “Why should I throw out the old system after I’ve put a bunch of time and money into it?”

Users can keep a lot of the work invested in the old SCADA system while upgrading to a modern one. The work on the old one becomes the foundation for the new one; there’s no need to start from scratch. Leverage prior HMI/SCADA investments as a reference, which will save a lot of time in an HMI/SCADA migration.

Figure 1: High-performance HMIs use plenty of gray, making it easy to see alerts and alarms in bright colors. Courtesy: Inductive Automation Figure 1: High-performance HMIs use plenty of gray, making it easy to see alerts and alarms in bright colors. Courtesy: Inductive Automation

A common problem with old HMI/SCADA systems is the original tag structures weren’t developed in an optimal manner. If that’s the case, users should think about standardization during an upgrade. Think about building the right objects that be can used repeatedly and standardizing HMI/SCADA tags across the enterprise. That way, if two like assets from two different sites are being compared, everything will look the same. It’s important to define the HMI/SCADA tag model and make it better.

Another important aspect is the data itself. Data is vital. And today, it’s easier than ever to share data with numerous business systems throughout the enterprise. Look hard at the data models, the HMI/SCADA architecture, and how data is being delivered to the enterprise. Improving standardization and leveraging objects create a single source of truth with HMI/SCADA data, with needed data context. The upgrade also can be the perfect time to move to edge computing and message queuing telemetry transport (MQTT) if this hasn’t already been done. With these in place, more data can be accessed, potentially at faster rates. This helps data delivery to more places within the organization. A new HMI/SCADA system provide more value after migration, which is especially valuable if for digital transformation for manufacturing or process facilities.

Holistic approach to HMI/SCADA system migrations

It’s no longer enough to put an HMI on the plant floor and have the users walk up to it and use it there. Today, companies must think about all the people that need the data, and how they’re going to get it to them. Companies have to ask, “Who is the audience?”

There are operational folks who need to see the process to control it, but now there are maintenance managers, C-level personnel and business needs. Dashboards and certain types of data can be very useful to all involved. Keeping them in mind when building an operational HMI/SCADA system will help companies get more value from it. Also, with people wanting data on phones and tablets, companies need to think about getting data to people in an optimal way for these devices.

For all these reasons, it’s important to take a holistic approach to an HMI/SCADA redesign during migration. Consider the enterprise during the upgrade. An often overlooked starting point in an HMI/SCADA migration and upgrade is to interview all involved about their needs. Interview the operator, for example, and ask, “What do you wish you had? What do you like in the system? What do you dislike? What would make your job better, faster, easier?” In this way, building the new HMI/SCADA system around the needs of the users.

Figure 2: Mobile-responsive design lets the HMI/SCADA designer design once, then see screens formatted perfectly on all devices. Courtesy: Inductive Automation Figure 2: Mobile-responsive design lets the HMI/SCADA designer design once, then see screens formatted perfectly on all devices. Courtesy: Inductive Automation

Five tips for optimizing HMI/SCADA screens

Once everyone’s needs have been determined, companies can focus on the user interface/user experience (UI/UX). One key point to remember is data itself is not information; data plus context is information. It’s important to add that context while removing uncertainty. The HMI/SCADA designs and screens should show users, immediately, what’s important. And remember that “less is more.” By decluttering screens and giving users less to look at, those users will be more effective at doing their jobs.

Here are five key areas to consider when upgrading HMI/SCADA screens:

1. Determine the navigation structure of HMI/SCADA designs.

In any HMI/SCADA application, good navigation is vital. Pick a layout that helps operators get to relevant data quickly and effectively. Should navigation go broad and shallow, or narrow and deep? Think about primary and secondary top headers. Do you want side navigation? Will you use tabs? All of these could be an ideal choice, depending on the complexity of display needs. Many of these can be used in combination.

2. Reduce HMI/SCADA screen cognitive load for the user.

Cognitive load is the effort required by the user to get a mental map of how a system works. The human brain can only process so much information at one time, so the interface should emphasize what’s important and get rid of extraneous information. Remove visual clutter, use neat alignment and grids and use only two or three fonts or font variations. To help users quickly absorb information, pair icons with text. Align text to the left and be consistent throughout the screens with style and terminology. For example, if two HMI/SCADA screen buttons have the same action, use the same term for both.

Figure 3: Moving analog indicators put a lot of information into a small amount of space on an HMI/SCADA screen. Courtesy: Inductive Automation Figure 3: Moving analog indicators put a lot of information into a small amount of space on an HMI/SCADA screen. Courtesy: Inductive Automation

3. Create HMI/SCADA visual hierarchy.

This helps users quickly recognize what information is most important. Emphasize the important elements by varying size, position, color and isolation.

4. Use high-performance HMI techniques.

These types of designs and displays help the user make the best decision in the shortest amount of time. High-performance HMIs often use grayscale rather than traditional graphics and bright colors. If flat graphics are used, and most of the screen is gray, it’s easier to draw the user’s attention to the most important information. The user’s eye will immediately be drawn to an item in red or orange, for example. Beyond color, certain graphic techniques help contextualize data for the user. These include sparkline charts, moving analog indicators and radar charts.

5. Leverage HMI/SCADA mobility.

These days, everyone expects to receive data on phones and tablets. With mobile-responsive design, companies can design the screens once and it will resize and reformat perfectly for any device being used. Mobile devices also have powerful features that can be used such as GPS, camera, Bluetooth LE, NFC and more. Users also can use the cloud for deploying read-only applications.

Figure 4: The HMI/SCADA redesign on the right allows operators to get a clearer picture, faster. Courtesy: Inductive Automation Figure 4: The HMI/SCADA redesign on the right allows operators to get a clearer picture, faster. Courtesy: Inductive Automation

New SCADA capabilities after an upgrade

SCADA has evolved. The data flowing through an HMI/SCADA system is now available to a much wider audience, allowing more people to make data-driven decisions. Companies upgrading their HMI/SCADA system should think about HMI/SCADA modernization for users’ need to leverage the latest technologies and get the data to more people. Use this opportunity correct the wrongs of the old HMI/SCADA system and build the new one for today’s requirements and needs. If companies are going to have the new car, put some new tires on it, too. It’ll go faster and farther.

Travis Cox is co-director of sales engineering at Inductive Automation, a CFE Media and Technology content partner. Edited by Chris Vavra, web content manager, Control Engineering, CFE Media and Technology,


Keywords: HMI, SCADA, control system


See additional SCADA stories at DCS, SCADA Controllers


What are the most important considerations when upgrading your SCADA system?


  • What is an HMI?

    HMI is an acronym for human-machine interface, which refers to the interface between a human operator and a machine or a control system (for discrete, process, hybrid or batch processes). It is a graphical interface that enables the operator to monitor and control processes, devices, or systems. An HMI can includes displays, touchscreens, buttons and other controls that enable the operator to interact with the system.

  • How is an OI device different than an HMI?

    HMI (human-machine interface) and OI (operator interface) are related terms, but they have different meanings.

    An HMI is the graphical interface that allows a human operator to interact with a control system, while an OI is the physical device that houses the HMI. An OI can be a standalone device or integrated into a larger control system and can include a display screen, buttons and other controls that the operator uses to interact with the system.

    In summary, the HMI is the graphical interface, while the OI is the physical device that houses the interface.

  • How does an HMI or OI communicate with a PLC or other control system?

    An HMI (human-machine interface) or OI (operator interface) communicates with a PLC (programmable logic controller) or other control system using one or more of the following communication protocols:

    1. RS232 or RS485 serial communication
    2. Ethernet or TCP/IP communication
    3. A variety of other industrial control-, device- and sensor-level communication protocols.

    The choice of communication protocol depends on the specific system requirements and the type of control system being used. The HMI or OI sends commands to the PLC or control system and receives data from it, allowing the operator to monitor and control processes. The communication between the HMI/OI and the control system can be either direct or through a network, depending on the system architecture.

  • Does an HMI need a PLC?

    Often an HMI (human-machine interface) is used with a PLC (programmable logic controller) or other industrial computing device to function in an industrial control system. The HMI serves as the graphical interface between the operator and the underlying control system, which is typically managed by a PLC. The PLC is responsible for monitoring inputs from sensors and other devices, executing control algorithms, and controlling outputs to actuators and other devices. Separating control logic from HMI functions is design strategy that lowers risk of downtime and can allow the controlled process to continue if the HMI fails.

Some FAQ content was compiled with the assistance of ChatGPT. Due to the limitations of AI tools, all content was edited and reviewed by our content team.

Related Resources