Top 10 Tips for Operator Interface Design

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.

Plan for portability. Assume an HMI application will one day run on another interface and design it to move. Using panels within the same family, such as the new HMi family from Eaton, makes your application as scalable as your hardware, because a click of a button resizes your screen.

Choose the right tools
Employing these tips and staying focused on the user will help you provide a useful, efficient application. Choosing the right tool can also help, because it will support the best practices described above. Eaton Corporation's new HMi family of analog touchscreen operator interfaces, for example, has an easy-to-use macro ability that can store application recipes, images, historical trends and alarm data. HMi stores an entire application, including images, so later editing does not require original source files, and its Picture Bank feature lets you upload and download images between the device and a PC.

When creating an application with Eaton's HMi operator interface products, many of the items from the list above are enabled by default. Elements are placed on the editing screen in a light-gray color, providing a neutral color base. You can set up the navigation menu, page changes, etc. on a single page in HMisoft, the product's editing software package, and then use HMi's base screen feature to automatically pick up the navigation menu, saving a lot of time.

Using the alarm frequency counter of the HMi, user navigation can be tracked, which can help in fine tuning the application. This feature allows you to simply count how many times a button is pressed, how many times a page is changed, how much time a certain page is displayed, and if the elements are displayed in the way the operator expected to use them.

Manufacturers occasionally need to upgrade or downsize operator interfaces, which can sometimes lead to distorted applications. The HMi family supports 4', 6', 8' and 10' device screens, and the ability to scale images automatically between screens with the click of a mouse. It will also convert color to blue mode or gray scale automatically. For the simplest conversion, always create applications using the 10' color model. From there they can be converted to any other mode and display size.

With HMi's image auto-fit feature, images can be sized to any desired size. This eliminates the need to edit images outside the software package to make them fit properly on the screen.

HMi from Eaton Corporation offers many other features that will give you the most efficient and effective operator interface for your application. For more information on HMi, please visit Eaton online at www.EatonElectrical.com/cehmi.

Overall, using the right techniques and proper tools should help make your operator interface project easier to implement and easier to maintain.

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

Eaton’s electrical business is a global leader in electrical control, power distribution, and industrial automation products and services. Through advanced product development, world-class manufacturing methods, and global engineering services and support, Eaton’s electrical business provides customer-driven solutions under brand names such as Cutler-Hammer®, Powerware®, Durant®, Heinemann®, Holec® and MEM®, which globally serve the changing needs of the industrial, utility, light commercial, residential, and OEM markets. For more information, visit www.EatonElectrical.com.

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