Designing the Operator Interface

Communicate clearly and configure quickly. Those are the dual goals of human machine interface (HMI) design. Accomplishing those goals depends on the techniques you choose and the tools you use. Here are ten quick tips for making sure your next operator interface project is a success.

1. Color scheme simplicity

Lay elements on a screen with a neutral color like gray. Then highlight items that need attention with a bright, bold color, such as yellow, red, or green. The neutral color minimizes distraction when an operator is doing his normal job, and the bright colors help to draw operator attention to extraordinary circumstances.

2. Information simplicity

Don't crowd the screen with information - place only the information for the current task. Putting more information than is needed on a screen forces operators to search for the one piece of information they need. This could lead to an operator pressing a similar button and making a mistake, or it can increase the time it takes for an operator to figure things out.

3. Consistency

Have a consistent set of menu buttons to help operators navigate easily from screen to screen, and keep them in the same place on each screen. This makes operations simple to understand and eases training.

4. Functional separation

Separate operator screens from maintenance and supervisor screens. When you consider who is using the device most of the day, you can tailor the screens for that user and help him be as efficient as possible. In relation to Tip #2, Information Simplicy, this enables you to create a separate set of screens for a particular user, if appropriate.

5. Test your knowledge

Capture how many times a button is pressed, a page is changed, which page is used most, etc.. Reviewing this data may surprise you. You might find that a piece of information not on the main page is more important than you thought after you review how many times someone goes to a different page to retrieve it. Such a review allows you to fine tune your application and help operators spend less time navigating from screen to screen.

6. Multilanguage considerations

Today's diverse working environment requires the use of multi-language support in operator interface products. If there's a chance your application will require translation, keep in mind that some languages might often take up a larger text area than the English equivalent. You should, therefore, make text areas large enough to accommodate various languages.

7. Watch your MLAs

Multi-letter acronyms and other abbreviations only work when all users understand their meaning, so spell out acronyms whenever possible. If you don't have enough room to place the actual phrase that would make sense, note that your screen might be too crowded or too small.

8. Use images

Most people use their vision more than any other sense, making pictures and illustrations a great way to quickly draw a user's attention. In a pump application, for example, you can use an illustration of the pump itself and highlight specific areas that need maintenance or adjustment.

9. Group data together

Just like placing a pump image on the screen to draw attention, you should place any elements associated with the pump close to the image. This could include the start and stop buttons and readouts for current, temperature, volts, hours run, etc. Placing this information elsewhere on the screen can lead to confusion and limit operator productivity.

10. Plan for change

Dare to assume that the application will eventually be used on a different size display. For whatever the reason—customer request, panel got smaller, panel got bigger, need color, don't want color, etc.—sometime there may be a need to use a different display. Prepare by keeping elements on the screen at a high contrast to the background. For example, use a black background and light-colored elements (like light gray) in your base design. This will be very visible on both color and gray-scale displays

by David Harris, Product Manager, Logic Control & Operator Interface Products, Eaton Corporation