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Unpacking ISA-101: Beyond the Misunderstood Grayscale

A Closer Look at HMI Levels and Their Importance

In the world of industrial automation, the ISA-101 standard often gets a bad rap. Many believe it merely advocates for the use of dull, grayscale graphics on Human Machine Interfaces (HMIs), which some operators find visually unappealing and uninspiring. However, this perception misses the broader and much more crucial intent of the standard: enhancing usability and promoting effective decision-making through well-organized HMI designs. This blog delves into the misunderstood elements of ISA-101, particularly focusing on the organization of HMIs into Levels 1, 2, 3, and 4, and explores why this hierarchical structuring is vital for operator situational awareness.

What is ISA-101?

ISA-101 provides a framework and guidelines for the design and implementation of HMIs in process industries. The standard emphasizes creating interfaces that improve the safety, efficiency, and reliability of operational responses.

One of the key aspects of ISA-101 is its approach to organizing HMI graphics across different levels. This hierarchical model is designed to deliver information in a structured manner, enhancing the operator’s ability to monitor, control, and respond to process conditions effectively.

Level 1: Process Overview
At the top of the hierarchy, Level 1 provides a high-level overview of the entire process or system. This macroscopic view is designed for quick scanning to ascertain overall system status and to identify any major issues that require attention. It’s typically used by supervisors or operators who are monitoring multiple processes or functional areas simultaneously, providing them with immediate access to critical alarms and operational statuses.

Level 2: Area Overview
Stepping down one level, Level 2 offers more detailed insights into specific areas or units of the process. This view allows operators to drill down into particular sections of the plant for a closer look at what’s happening. While it still maintains a broad perspective, it provides enough detail to facilitate decisions on operational adjustments or interventions without overwhelming the user with data.

Level 3: Detailed Process Control
Level 3 is where operators interact most frequently. This level presents detailed control screens for specific equipment or process parts. Operators can control individual components such as pumps, valves, or boilers from this level, equipped with the necessary real-time data, controls, and detailed operational statuses. It is designed for active engagement with the process, where most routine operations are executed.

Level 4: Maintenance, Diagnostics, and Configuration
Finally, Level 4 screens are used for settings, maintenance activities, system diagnostics, and configuration tasks and is often associated with faceplate controls for devices, sequences, unit parameters, etc. These interfaces are less frequently accessed and are typically restricted to specialized personnel. This level includes detailed settings that can adjust the parameters of the process or equipment, and it provides comprehensive diagnostic data useful for troubleshooting and maintenance.

Why This Organization Matters

The layered approach outlined by ISA-101 is critical for maintaining situational awareness. Each level is designed to provide information that is contextually relevant to specific operational needs and user roles. This not only ensures that operators are not overwhelmed by unnecessary data but also enables them to quickly and accurately assess operational situations and make informed decisions.


ISA-101 is more than just a guideline for using grayscale graphics—it is a comprehensive approach to HMI design that enhances operator effectiveness and safety. By understanding and implementing the level-based organization of HMIs as prescribed by ISA-101, process industries can significantly improve their operational clarity and response effectiveness. It’s time to move beyond the misconceptions and appreciate the depth and utility of ISA-101 in crafting superior human-machine interfaces.


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