"When computers were first put into use in industrial processes for the purpose of HMI they had only the most basic graphical capabilities. Eventually the computing systems gained more and more graphical capability and the HMI applications also began to leverage these improvements with little thought of whether that was the right choice to make. It has become commonplace for the HMI applications to become a show piece that emulates the process in a very visual manner and often that visual presentation is used to justify the automation investment to key stakeholders. However, these very elaborate visual approaches often impair the operator’s ability to ascertain the current situation and ultimately make key decisions to maximize the business value of the application.
|Figure 10 - Example of Poor Color Usage|
In Figure 10 the process is displayed with three dimensional pipes and flanges that offer the operator no real information, gauges with artificial glare applied, the color red has several meanings, and a variety of other bad practices. In the version of that same graphic shown in Figure 11, there is a much better use of color. Often people will comment that the graphic designed for better situational awareness is boring and the truth of the matter is that graphics that effectively communicate the state of the process to the operator are boring. Through a limited use of color the operator’s attention can be driven to the point in the process that has deviated from a normal or expected state. When the system state is completely within expected norms the process graphics should not emphasize and draw the operator’s attention to these normal conditions as that only serves to overload the operators attention. The utilization of animations should be with the deliberate intent of drawing the operator’s attention and not just to make an impressive visualization. If operators are being distracted by spinning pumps or gradient shaded lights when they should be focusing on a process value drifting outside of operational limits then the HMI is not likely to result in the improved ability of achieving the business goals or safe operation. While color should never be the only method used to communicate a value or state it can be a very effective tool for driving the user’s attention. To ensure an optimal HMI design it is very important to establish and strictly utilize color standards. When designing the color standards that will be used in the HMI application it is very important to prevent an ambiguous use of colors. If the same color has multiple meanings then the operator will often become confused about the information that is being communicated. A significant concern when choosing colors is that color blindness affects as many as 8 percent of men and 0.5 percent of women. A very effective method for combating color blindness is to leverage a variation of color saturation. While color blindness affects the hues of the color perceived by the user these people are still capable of discerning variations in color saturation.
|Figure 11:Example of Better Color Usage|
When choosing a color palette one approach is to use only grays unless an abnormal situation is to be communicated. It is possible to use alternate colors in the palette as in shown in Figure 12 but it is very important to ensure that the operator be able to readily distinguish a normal state from an alarm state with no ambiguity. There is no one color palette that is universally correct for all applications but by following these simple recommendations you can ensure that your color palette is working for you, instead of against you”.
Source: Krajewski, John (“Situational Awareness The Next Leap in Industrial Human Machine Interface Design”
In the next few posts I will provide a detail view at other tools and techniques available (actionable alarm management, and effective design elements) to improve the operations outcomes mentioned above.
- Top 5 trends that currently drive the need of the modern industrial HMI application
- The Impact of Human Error in Industrial Automation
- A Results Driven Approach to improving overall HMI design
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