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.
Aligning replacements
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.”
High-performance HMIs
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.”
