In 2015, when the ISA-101 HMI Design Standard was published, it provided overall design guidance and a workflow for developing and managing HMI systems, including change management, and a framework for order for HMI. While the standard significantly improved the day-to-day operations of HMIs, the focus now needs to shift to operator efficiency and creating screens for situational awareness and operator tasks. In addition, companies need to go beyond ISA-101 to train operators to use the HMIs. Facility owners must develop a clear HMI philosophy document and style guide for the HMI system. To further improve efficiency and decrease human error, reusable software toolkits of screen elements should be developed. The goal is to produce a true high-performance HMI.
A recent white paper from Emerson Discrete Automation addresses this topic with Best Design Practices: How to Create High Performance HMI to Enhance Operator Efficiency. This paper gives specific instructions for HMI details such as color and graphics, how to turn data into actionable information, even to inexperienced workers, interface technologies such as WPF, web-based and mobile-ready HMI, and even augmented reality. All of these are based on certain philosophies and fundamentals of design.
The aim of high performance HMI is to provide simplified interfaces that speed operator response time, and improve problem and alarm resolution, while reducing errors. Instead of portraying a real-world representation of the machine or process, operators need information reflected in a manner that is easy to scan for anomalies and identify areas that require further investigation and action. High performance HMIs incorporate application-specific and personalized screens that help operators achieve a purpose, spend less time searching and navigating, and allow them to make better decisions faster. Keeping the HMI simple also makes it easier to train the next generation of operators. An effective interface is easy to learn, leads to faster reaction time, and enables safer operations and higher productivity.
Basic design concepts start by saying that one of the main principles is using moving analog indicators instead of just numerical displays. The analog indicators will display the span of an instrument, show abnormally high and low values, and high-high and low-low process values. With these analog indicators, operators only need a quick glance to understand the status of the process. Likewise, making trends available should be a top priority. Other basic concepts include but aren’t limited to:
- Use of a tight scale makes change immediately obvious to the operator without the need for keystrokes.
- The use of color is fundamental to high performance HMI. Colors need to be used consistently.
- The background color should be light gray, helping to reduce glare and operator fatigue.
- Foreground colors should be kept to a minimum and used sparingly to indicate abnormal situations and to draw the attention of the operator.
- Line thickness should also be consistent, and styles restricted to solid, dash and dots.
- Arrows indicating process direction must be kept to a minimum to decrease confusion.
- Process equipment and vessels should be drawn in 2D, avoiding shading and gradients.
- Avoid overcomplicated equipment drawings with unnecessary detail, such as inner workings.
- Focus should instead be to display only elements that enable the operator to know what is happening.
- Process flow should be consistent across screens, and in general, flow from left to right, vapors up and liquids down.
- Minimize the use of static text that names or describes objects. Keep abbreviations consistent.
- Live data should be depicted differently from static text with a different color (usually blue).
- Live data should have units of measurement shown.
The white paper has a lot more useful and practical information and you can download a copy here to find tips and techniques that are specific to your HMI requirements.