The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control and embedded systems. Control Engineering answers questions from readers of Control Engineering's print and online magazines, newsletters and other publications.

Why can't we have more exciting graphics?

HMIs can have spectacular graphics. Why shouldn't we use them?

February 18, 2011


Dear Control Engineering: I was reading the article Gray Backgrounds for DCS Operating Displays. Why is operator response so important? Aren’t most problems caused by the equipment?

The Abnormal Situation Management Consortium says that people factors account for 42% of incidents, which is why the group spends so much time on operator training and how individuals interface with the control system. (If you’re curious, equipment factors account for 36% of incidents, and process factors for only 22%.)

If an operator has to look at an HMI screen and ask him or herself what that blinking red thing means, it means that the operator is not adequately trained, or that the HMI graphic is not consistent in its use of color. Any time spent gathering thoughts and interpreting graphics simply slows the response and allows the problem to go on longer, potentially escalating in scale and damage. Worse yet, an operator may take the wrong action if he or she doesn't understand immediately what the display is trying to say. Consistency is critical.

Peter Welander, pwelander(at)cfemedia.com