In the stone ages of DCS design, text options were few – full versus half size was about the only decision required. But like many other issues in interface design, the advances in technology have allowed greater flexibility, but also more decisions, of which text size and style are only a couple. Which is best? Under a grant from Microsoft, research into font design and display parameters was conducted (Sheedy, J.E., Subbaram, M.V., Zimmerman, A.B., and Hayes, J.R, “Text Legibility and the Letter Superiority Effect”, Human factors, Vol. 47, No. 4, Winter 2006, pp 797-815).
The bottom line is that fonts should be at least nine pixels in height, in Verdana style with sub-pixel font smoothing. This is of course for viewing computer displays from a normal seated distance; a larger font would be needed if it were to be viewed from farther away. Like much research, some of the results were counter-intuitive. While two of the sans serif fonts had the best legibility (Verdana & Arial), another had the worst (Franklin), indicating that the presence of serifs (the little curls at the ends of the letters) are not a major contributor to legibility.
Beville Engineering has helped numerous petrochemical companies to resolve these types of issues in the development of graphics standards. Our most recent effort has produced an electronic document for ease in maintenance and distribution. The font used? Why, Verdana of course!
Copyright © 2006 Beville Engineering, Inc., All Rights Reserved
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This year's Fall meeting for the Center for Operator Performance will be October 24-26 in Corpus Christi. For more information, please contact Lisa Via. Guests are always welcome!
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David Strobhar's book, "Human Factors in Process Plant Operation," is now available in both hardcover and Kindle e-book.
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