When designing a high performance HMI, the goal is to enable the controller to see an abnormal operating condition prior to reaching an alarm limit. Sounds easy right? Well maybe not.
Historically, HMIs have been mostly line drawings and numbers with alarm indicated in a banner. While numbers are critical to diagnostics, they are problematic when it comes to situation awareness. In pipeline operations, the controller first wants to know is my area of responsibility normal or abnormal. Working through a set of numbers to make this determination increases cognitive load negatively impacting workload and fatigue. Properly designed graphics can make this determination intuitive. Anyone who has looked at a familiar trend, knows immediately that the brain can process a graphic more quickly and intuitively than numbers alone.
Developing a high quality situation awareness approach requires a firm philosophy about HMI design and a collaborative development approach. While the goal is to see abnormal before reaching an alarm limit, it is impossible to develop an HMI that always achieves this goal. Therefore, implementing a process of continuous improvement is necessary so that the HMI can improve as controller gain operating experience.