Quick Tips For HMI Development

Although developing a human-machine interface (HMI) is often the last part of a control-system-integration project, it’s vital to the success of an automation system.

According to Justin Gilg of systems-integrator Huffman Engineering Inc. (huffmaneng.com, Lincoln, NE), a successful HMI design requires restraint. He offered the following tips.

Consistency

In most cases, new HMIs should be modeled with the look and functionality of others in use at the site. Consistency is key. If the menu appears across the top of existing HMIs, follow that format. The same goes for other aspects of the display. Uniformity is important for new-employee training and the operators’ ability to move to unfamiliar equipment.

Developing HMIs for facilities that don’t already have them is another matter. This situation allows more creativity, as well as reliance on experience with similar applications. Consistency in menu placement, color scheme, and graphics from screen to screen is still crucial.

Color

If the site has a standard for color, adhere to it. If not, there’s usually an industry standard. Limit the use of color so it captures operator attention. Colors designated for alarms should only be used for that purpose. Color should not be the only discriminator of an important status condition. Use text to call it out. Complement the red-color button with the word “stop.” To draw attention to alarms and faults, add blinking. Don’t overlook the possibility of color blindness in operators. Red-green color blindness is the most common type for males, followed by blue-yellow. If it’s necessary to use the color combinations together, make one a dark shade and one a light shade so they are distinct.

Graphics

High-performance graphics should improve an operator’s situational awareness, not be a distraction. While access to an abundance of data is alluring, use it judiciously. The goal is to make the process easier for operators, not overwhelm them. Fancy or overly detailed graphics showing every part of a machine can become clutter and lead to confusion.

Simplicity

Keep it simple. Display only what operators need to know, and make the data useful. Don’t expect operators to know what a process value means. Instead, show where it is relative to a good process-value range. Abnormal conditions need to be obvious. Color must be used sparingly, consistently, and effectively. Consider the number of screens. Adding too many can hamper operator control. EP

For more information regarding HMI development, click here.