5 Tips for a Better Human Machine Interface (HMI)

October 6, 2015 - Author: Greg Larson, Project Manager

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HMI screens are used widely in industry as a means to control process or equipment, but there seems to be as many ways to design them as there are stars in the sky. In my nearly 20 years of doing controls, I have seen some pretty awful looking screens. Likewise, I have seen some very well designed screens. The question is, what is it that makes for a well-designed screen? The answer is fairly simple. There are 5 simple tips that I use to make sure I deliver a clean, professional, and most importantly, useful and informative HMI application.

1) Use a Light, Neutral Color for the Background, Preferably Light Grey

Studies have found that this is easier on the eye than white, black, or flashy colors. The use of bright colors may clash with other display elements and result in a display that is difficult to read or understand.

2) Use Color Intelligently

I am a big fan of color in an HMI if it is used intelligently. Colors should have a specific meaning. Don’t add them just for looks. Examples would be Red for Alarms/Stops, Yellow for warnings or alerts, Green for running or safe. Often, I will use color with numeric displays. I will use different colors to differentiate between process values and set points. This way you can tell at a glance, which displays can be edited.

3) Be Consistent When Placing Navigation and Control Buttons on the Screen

I have had clients complain about having to search for controls because the location changes from screen to screen. Place buttons in a consistent order and position at the top of the screens whenever possible.

4) Don’t Overload a Screen

Only show on a single screen the most important pieces on information. For example, a chilled water loop you will want to show basic loop diagram, chiller status, pump status, temperature, and pressure. Other parameters such as pump speed or amperage should be on a pop-up screen or other location so that it doesn’t obscure what you really need to see. No one wants to have to hunt for the information they need.

5) Listen to the Operator when Designing the Screen

This is a tough one, but the operator is the person who will be using this on a day-to-day basis and if you want the project to be truly successful, get his or her input. They usually aren’t the decision makers, but operators will often provide feedback to management once the project is delivered, and if he is complaining about the interface, that may impact their willingness to call you for the next opportunity.

These are not hard and fast rules, nor is it a complete list of things to pay attention to. However, if you follow these 5 tips, your application will look much more attractive and professional.


References

HMI Design: An Analysis of a Good Display for Seamless Integration Between User Understanding and Automatic Controls

Guidelines for Effective Schematic HMI Design


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