The ISA-101.01 standard organizes operator displays into a numbered four-level structure, from a broad Level 1 overview down to a narrow Level 4 diagnostic screen. Each level has a defined purpose and a defined set of content, and navigation flows top-down so that an operator moves from the big picture to the specific cause. This numbered taxonomy is what gives a large display set a consistent skeleton instead of a sprawl of unrelated screens.
ISA-101 Display Level 1/2/3/4 in one line: ISA-101 display levels are the four numbered display classes defined in the ISA-101.01 standard: Level 1 area or process overview, Level 2 process control, Level 3 equipment or system detail, and Level 4 diagnostic and support. Lower levels are broader and monitored constantly; higher levels are narrower and opened on demand as an operator drills into a problem.
Level 1 is the area or process overview. Its job is at-a-glance awareness across a large scope, such as a whole facility or a major unit, so it emphasizes a small number of key performance and safety indicators, aggregated status, and abnormal-situation cues rather than fine detail. An operator watching Level 1 should be able to tell that everything is normal, or that a specific area needs attention, without reading numbers off individual instruments.
Level 2 is the main process control level, and it is where operators spend most of their time. A Level 2 display covers a coherent process area or unit in enough detail to run it: the working equipment, the key control loops, live values, and the controls to act on them. This is the level at which routine adjustments and most abnormal-situation responses are actually carried out, so it balances completeness with the restraint of good high-performance design.
Level 3 is the detailed display for a single piece of equipment or a group of closely related loops, giving the deeper parameters, secondary values, and supporting information that Level 2 deliberately omits. Level 4 goes further still into diagnostics and support: instrument health, device status, configuration and troubleshooting information, and reference material consulted only when needed. The numbering encodes a rule of thumb - the higher the level, the narrower the scope and the less often it is watched.
The four levels are meant to be traversed, not treated as parallel silos. The intended flow is top-down: an operator scanning the Level 1 overview notices an area turning abnormal, opens the Level 2 display for that area to work the process and see what is happening, drills into a Level 3 detail display for the specific equipment implicated, and if necessary reaches a Level 4 diagnostic to check an instrument or device. Each level hands off cleanly to the next.
This mirrors how an operator's attention should move during an upset - from the broad picture, to the affected area, to the specific cause. A flat set of screens forces the operator to already know which display to open, which is exactly the knowledge that fails under stress. The numbered levels instead let the overview point toward trouble and each screen provide a natural path inward, so navigation supports diagnosis rather than depending on it.
For the structure to work, the standard expects the navigation itself to be consistent: a predictable way to move up and down levels, to reach the display for a given tag from wherever the operator is, and to return to the overview. The point of anchoring displays to the ISA-101 levels is not the numbering for its own sake but the guarantee that every operator, on every screen, knows where they are in the hierarchy and how to get to the next relevant view.
For a Merobix cloud SCADA operator, the four-level model gives concrete guidance for building a display set that scales. The Level 1 overview becomes the landing screen, summarizing sites, wells, or units so that a single operator responsible for a large remote fleet can see at a glance which locations are healthy. Because it loads first and is watched constantly, it is designed to be light and fast, showing status and exceptions rather than dense instrumentation.
Level 2 screens map naturally to individual sites or units in the field, each holding the working equipment and control loops for that location. From a browser, an operator moves from the fleet overview into the site that raised an exception, works the process there, and only then opens Level 3 detail on the specific pump, compressor, or separator involved. Keeping this drill-down consistent across every site means an operator can walk into any location's screens and immediately know how to navigate them.
Level 4 in a cloud context often carries the diagnostics that remote operation depends on: communication status to the RTU or PLC, device and sensor health, and the supporting information needed to decide whether a bad reading is a process problem or a telemetry problem. Anchoring these to a defined level keeps them out of the way during normal operation while making them reliably reachable when an operator needs to distinguish a real upset from a data-quality issue, which is a frequent question when the field is hundreds of miles from the screen.
Level 1 is the broad overview for at-a-glance awareness across a facility or large area, emphasizing key indicators and abnormal cues rather than detail. Level 2 is the main process control level for a single unit or area, with the values and controls an operator uses to run it. Level 1 tells you where to look; Level 2 is where you act.
Level 4 holds diagnostic and support information: instrument and device health, communication and configuration status, troubleshooting detail, and reference material. It has the narrowest scope and is consulted on demand rather than watched continuously. In a remote or cloud SCADA, Level 4 often carries telemetry and device-health data that helps an operator tell a real process problem from a data-quality issue.
The four-level model is a framework, and a given system uses as many levels as its scope needs. A small skid might not require a full facility overview, while a large field benefits from all four. What the standard encourages is that whatever levels exist are used consistently, with a defined purpose per level and predictable navigation between them.
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