Most customers will never care about your design logic with its perfect structure, adherence to precise standards, or excellent comments and description. Nor will they be aware of that magnificent script running oh-so-silently in the background and keeping their operations from falling into disarray. But they will see the human-machine interface (HMI) screens. Every person walking through that plant will see the HMI, whether they’re in the grade school tour group or the curious execs visiting from corporate.
HMI is not all about flashing lights, bells and whistles. There’s a plethora of information a programmer can display on an HMI screen. But just because a programmers can display information, it doesn’t mean they should. The goal of an HMI screen should always be to present information in a logical and orderly manner, where the most important information or severe issue displays up front and grabs the operator’s attention.
There is no one perfect approach to designing HMI screens. There is, however, one basic, never-to-be ignored rule: Get operator input right from the beginning. The system operators will be the people interfacing with the system every day, and it’s critical to consult with them early in the design and review process.
Wise engineers adapt to individual customers and present their information in the best way for their particular needs, displaying only necessary information. A bad screen will be busy and disorganized, might ignore standards, or be overly animated or distracting. Yes, alarms should alarm and animation can direct the user to important information, but they should never be there for their own sake, no matter how tempting that might be. Remember also that good HMI design involves more than simply displaying information. Careful designers will also consider process flow, which will impact how they organize and position data on screen and ensure maximum usability.
HMI design provides us right-brain engineering types with a rare opportunity to let loose that left cranial occupant and create actual art—functional art that will possibly exist for years (or until that next obsolescence project comes around, but that’s a whole other blog topic). Generations of operators will tell stories about the Michelangelo of HMI Screen Design and the masterpieces that came from that artist’s keyboard and mouse.
Well…OK. Not really. But you get the idea. If you do your job right, you will open a world of true process understanding and interaction for your operators—a world where the information is presented in such a clear, concise and usable manner that training is a breeze; a world where onlookers near and far can identify when there is an alarm that needs immediate attention; a world where operators become more productive simply by using your design.
Let loose those creative juices and make HMI screen design the art of concise presentation of useful information. Visualize the process! Learn more about how Avanceon employs accepted standards in its designs.
Stephen Fischer is a control engineer at Avanceon, a certified member of the Control System Integrators Association (CSIA). For more information about Avanceon, visit its profile on the Industrial Automation Exchange.