When it comes to upgrading human machine interface (HMI) technology, the question of where to begin often depends upon where you’re starting from to determine how to achieve your near-term HMI goals.
Scalability, must-have features, enterprise integration, and, of course, cost are among the biggest factors end users should have at the top of their list, according to Loren Schmidt, lead control systems analyst for system integrator Interstates. He adds that it’s also important to consider issues such as mobility, which “some HMI software packages make easy, while others don’t.”
Meanwhile, some HMIs handle data storage and display historical data better than many competitors, but their “price is often too high for many end users,” Schmidt adds.
Where to begin
The first thing to realize is that any HMI hardware and software considerations should address company strategy as well as application specifics.
“Most modern HMI software can adapt to various applications, though you should pick something matching your SCADA strategy so you can merge applications for consistency and licensing savings later,” says Sam Russem, senior director for smart manufacturing solutions at system integrator Grantek. “Your application and [operating] environment can have huge implications for the hardware you choose.”
A key role for system integrators is to help answer end users’ questions about HMI hardware and software, but it’s always smart to be generally knowledgeable about your requirements and plans to ensure long-term benefits.
For example, with software, consider your company’s near-term goals. Is ease of development in the HMI environment important to your plans? Since licensing costs can vary widely, what is your acceptable framework for such costs? Do specific standards apply to your operations and does the HMI software need to support them? Is historical data logging for analysis something you want from your HMI?
When end users can answer these kinds of questions, it helps us “narrow down the list of potential software platforms to the best one,” says Nicholas Imfeld, operations manager with system integrator Avanceon.
If you need to upgrade HMI hardware and software for a particular machine or system, it often makes sense to start with the hardware, since physical features can immediately impact decisions based on fit with legacy equipment.
Beyond form and fit factors, determine if the hardware platform supports open systems or is restricted to vendor-supplied platforms.
Self-contained, stand-alone systems often tend to favor vendor hardware, require little IT infrastructure, and often don't require runtime licenses. Larger, supervisory control and data acquisition (SCADA) systems, however, often run in a Windows-based environment and need more IT support and licensing.
Imfeld says, if you’re currently running a Windows-based HMI/SCADA environment, determine first what kind of hardware makes the most sense on the plant floor. For example, will you use thin-client terminals or PCs?
Using thin clients means “one or more Windows server class machines will be required,” says Imfeld. And regardless of whether you choose thin clients or PCs, the number of servers and terminals will depend on the HMI application. Some HMI systems can require a computer to function as the HMI server, a computer to serve as the communication channel between the HMI and the PLCs, a computer to host the HMI, and a computer for historical data storage.
While more open, Windows-based HMIs tend to dominate, vendor hardware-based systems also are common. When considering such HMIs, its important to focus on choosing software and hardware that provide the functionality and dependability you require.
Vendor-based systems tend to provide a larger runway [for use], Imfeld says, meaning that users can rely on many years of support for combined hardware and software HMI systems. Depending on the application and company strategy, some integrators recommend that HMI hardware and software be upgraded together. But the advance of open systems use, driven by end users’ preference for wider software options, is leading an increasing number of manufacturers looking to avoid vendor lock -in.
“Most hardware is designed to work with a certain software,” says Interstates’ Schmidt. “To avoid adding additional labor cost by trying to make a different software work, we go with the software that is designed for the hardware when it comes to touch panel HMIs.”
Interstates also supports industrial PC-based systems with industrial touch screen monitors. “This enables us to use any HMI software solution and still have an HMI out on the plant floor,” Schmidt says.
Making this decision ultimately depends upon the hardware you want to use, but ongoing supply chain factors can influence this decision.
“There are pros and cons to buying HMI hardware and software together or separately,” Russem says. “Some HMIs are designed to run a single piece of software, so you won’t need to worry about compatibility, and you have one place to go if you need support. But having separate HMI hardware and software can give you additional flexibility. If you have a production-critical HMI fail today and the hardware to replace it isn’t available, you may be forced to move to new hardware and rewrite your software. If you have software that’s compatible with hardware from a variety of vendors, you have more flexibility in your hardware choices.”
While the question of whether to move toward use of high-performance HMI graphics once was hotly debated, some integrators say this question has become less of a conundrum for end users.
“I’m in favor of using high-performance graphics whenever possible,” says Imfeld. “My main driver is ease of information transmission. The example I use is this: If I am walking through the production area and glance at an HMI terminal, I should be able to tell from across the room if I need to walk over and address something on the HMI based on a splash of yellow or red.”
Russem is also an advocate for high-performance HMI screens. “HMIs are tools to help run a machine or process, and the more clearly they can point operators to exactly the information they need to do their job and keep the process running, the better,” he says.
Schmidt adds that “we’re not seeing a big drive by customers to have flashy, colorful graphics. Our attention is on gathering and displaying pertinent information to help operators in their day-to-day tasks. So, the ability for HMI hardware and software to be powerful enough to handle that data is key. Features like trending and tracking historical data are also really important now.”