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Attract Operators' Attention

If you’re seeking best-practices standards for designing graphical operator-interface displays, you won’t find them. Edward Tufte’s book “Envisioning Information” has useful information, though, notes Kevin Harris, director of the Honeywell Inc. (www.honeywell.com)-led Abnormal Situation Management Consortium (www.asmconsortium.org), in Phoenix.

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Engineering Equipment and Materials Users Association (www.eemua.co.uk) also offers guidance in its Publication 201, “Plant Control Desks and the Human-Computer Interface: A Guide to Design, Operational and Human-Computer Interface Issues.”

But if you search, some consistent practices surface. Simplicity ranks first, states Donna Smalls, HMI/SCADA (human-machine interface/supervisory control and data acquisition) product manager within the Automation & Safety Group of Schneider Electric’s (www.schneider-electric.com) North American Operating Division, Raleigh, N.C. She also lists using state-of-the-art technology and providing remote functionality. Smalls identifies a general trend to locate control system intelligence in the terminals.

Emerging as a best practice is designing terminals to support functions once reserved for high-end personal computers, Smalls adds. For example, she notes that “a terminal range of up to 65,535 colors allows it to realistically display photographs and images. This is an important feature when images are being used to aid in process monitoring, maintenance and fault finding.” 

Make it boring

Harris agrees that appropriate colors must be used for alarms, piping and screen backgrounds. “More traditional ones (operator interfaces) look very snappy, but that can be a problem. What we’ve found is that what works best for
background is a color that’s actually boring.” He recommends light gray or some variation. 

Regardless of color choices, though, he mentions other major best practices. One is screen navigation to provide efficient workflow. Another one he emphasizes is consistency in everything, such as screen position of items, screen and font colors, fonts, icons and the like. John Roberts, technical specialist with Roswell, Ga.-based vendor B&R Industrial Automation Corp. (www.br-automation.com), agrees about consistency’s role, calling it the most important. “The screen needs to be clear and concise for a particular setup for one station or within an industry.” Having
standardized-looking pages makes display use easier, he adds.

Another design feature making displays easier to use is interoperability. Wonderware (www.wonderware.com), Lake Forest, Calif., seeks this in operator-interface displays that it buys and to which it adds software, explains Ann Ke, Wonderware product manager for industrial computers. Screen size is important, she adds, because end-users want to display lots of information, and “need a lot of real estate to do that.”

For touchscreens, one best practice is providing enough space between icons so the touch zones don’t overlap, explains Steven Abramovich, vice president of sales and marketing for Elo TouchSystems (www.elotouch.com), a touchscreen provider based in Menlo Park, Calif. Once the icon/button activates, “typically, you want it to change color—or ‘explode,’ meaning it gets larger and then recedes,” he says. “You could give a text message, such as ‘OK?’ Or put a check mark in it. But something to show [the operator made] a legitimate touch.”

Not to be overlooked are safety and protection. Temperature variations can affect display performance, notes Todd Christensen, director of marketing for operator interface terminal maker QSI Corp. (www.qsicorp.com), Salt Lake City, Utah. “Extreme cold will slow the crystals in the LCD (liquid crystal display) to function very slowly or not at all.” Roberts mentions adhering to NEMA 4, the National Electric Manufacturers Association Type 4 Enclosures standards; and IP65, the International Electrotechnical Commission’s (IEC) Ingress Protection (IP) 65 rating through IEC Standard 529.

Whatever best practices may be, they focus on operating environments and operators. “You want do something to attract their attention,” declares Harris about designing and coloring the displays for those who watch plants through those screens. 

 

C. Kenna Amos,

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