A Preference for Grayscale HMIs

Nov. 30, 2021
Why a wastewater reclamation department designed its human machine interfaces without color-intensive, action-packed graphics.

Operators at the Pima County Regional Wastewater Reclamation Department are among a growing group of automation professionals who have learned firsthand that good human-machine interface (HMI) graphics are really about effectiveness, not attractiveness. They urge automation professionals to adopt a graphical-design strategy that focuses the operators’ attention on the things that require it by taking into account human factors and the principles of situational awareness to keep safety and productivity high.

The has led to the emergence of a simpler, grayer, almost minimalistic look designed to draw the attention of operators and technicians to situations that require their intervention. Such designs typically depict backgrounds and items running normally in shades of gray and reserve color and motion for highlighting abnormalities.

Because the goal is to draw attention only to those situations that require action, this design philosophy uses color, shapes, and motion sparingly so they will stand out against the background when needed. “Color can be very effective in catching the attention of an operator, but overuse greatly diminishes its ability to capture the operator’s attention,” notes John Krajewski, vice president of product management at Aveva. “When it’s important to keep the operator focused on the most important task or situation, a limited use of color is most effective.”

Read  more about Pima County's use of high-performance HMIs.

This design philosophy played an important role in the upgrade undertaken by Pima County to improve phosphorus and nitrogen removal at its Tres Rios Water Reclamation Facility in Tucson, Ariz. Because success depended upon the operators’ ability to manage the automation in the facility, the upgrade included the HMIs on its supervisory control and data acquisition (SCADA) system from Aveva. The old design had been overwhelming the operators with too much data and too many nuisance alarms.

Using Aveva InTouch software, Pima County’s engineering staff was able to avoid this problem by applying the principles of situational awareness. The window structure, color scheme and alarm hierarchy of the HMIs not only present information about the processes and systems in the context of their operating environment, but also highlight abnormal activity. This enhances the staff’s ability to perceive and understand what is happening in the water reclamation facility and focuses its attention on what needs to be done.

As a consequence, key alarms no longer get lumped in with the nuisance alarms. Operators now address them right away before they have time to fester and develop into serious problems.

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