What is the automation pyramid?
The automation pyramid is a hierarchical model that divides the systems of an industrial enterprise into levels, from sensors and actuators in the process, through PLC, SCADA and MES, up to the company’s ERP system. The pyramid shape shows that at the bottom many devices handle large volumes of fast, simple signals, while at the top a few systems make decisions on aggregated information over days and weeks. The model is the common language of industrial automation and a starting point for OT convergence, Industry 4.0 and network segmentation.
The model describes how data and functions are organised from Sensor to boardroom.
The pyramid is not a formal standard. It is closely related to the Purdue Model and to the functional hierarchy of ISA-95 (IEC 62264), but it is not the same thing.
🧠 Where does the automation pyramid come from?
The concept emerged in the 1980s, when factories were automating rapidly under the banner of Computer Integrated Manufacturing (CIM). The first pyramids covered only the lower layers: inputs and outputs, control and operator interface. Planning sat in the related “CIM pyramid”. Since the 1990s most diagrams have shown all layers in a single figure, because the systems themselves were growing together.
In parallel, Purdue University published the Reference Model for Computer Integrated Manufacturing with ISA in 1989, elaborated in 1992 into the Purdue Enterprise Reference Architecture. That level structure became the basis of ISA-95, whose Part 1 appeared in 2000 and which was adopted internationally as IEC 62264. ISA-95 fixed the numbering of levels 0 to 4 internationally and focuses mainly on the interface between levels 3 and 4.
The literature contains more than 25 variants of the pyramid, with four to six layers and differing names. Some authors merge the enterprise and operations levels into a single management layer; others add a cell level. The boundaries are therefore not sharp.
🧱 What levels does the automation pyramid have?
The most widely used version has five levels, numbered as in the Purdue model:
| Level | Name | Function | Examples | Time scale |
|---|---|---|---|---|
| 0 | Field or process level | Measuring and switching in the physical process | Sensor, Actuator, motors, valves, Remote IO | Milliseconds |
| 1 | Control level | Control and regulation | PLC, VFD, DCS controllers | Milliseconds to seconds |
| 2 | Supervisory level | Operation, visualisation and alarming | SCADA, HMI, DCS operator stations | Seconds |
| 3 | Operations level | Production execution, quality, maintenance | MES, Batch Control, Historian, LIMS, CMMS | Minutes to days |
| 4 | Enterprise level | Planning, purchasing, sales and finance | ERP, WMS, QMS | Days to months |
In the German literature, where the term Automatisierungspyramide is most common, the lowest level is often split further into a sensor/actuator level (binary signals via AS-Interface or IO-Link) and a field level with I/O modules and fieldbuses.
Watch out for the difference in numbering. In the pyramid and the Purdue model the PLC sits at level 1. ISA-95 assigns automated control functionally to level 2, reserves level 1 for sensing and manipulating the process, and treats level 0 as the physical process itself. Agree in your projects which model you mean.
🔄 How does it differ from the Purdue model and ISA-95?
The three models share the same hierarchical idea but serve different purposes. RAMI 4.0 later built on them:
| Model | Status | Purpose | Characteristic |
|---|---|---|---|
| Automation pyramid | Informal model, many variants | Explaining and classifying systems | Didactic, emphasis on data volume and time scale |
| Purdue Model | Reference model (1989/1992) | Integration, later security | Level 5 for enterprise IT and level 3.5 for the industrial DMZ |
| ISA-95 / IEC 62264 | International standard | Integrating ERP and production | Functions, objects and messages between levels 3 and 4 |
| RAMI 4.0 | DIN SPEC 91345 (2016) | Reference architecture for Industry 4.0 | Hierarchy axis extended with Product and Connected World |
The Purdue model is therefore not a more modern alternative but the very origin of the same layering. Security practice later added zones and an IDMZ to it. RAMI 4.0 adopts the levels of IEC 62264 and IEC 61512 (ISA-88) as one of its three axes.
📡 How do the levels communicate?
Traditionally, data flows upwards layer by layer and commands flow downwards. At each layer data is filtered, summarised and enriched: thousands of measurements per second become a trend, a batch report and ultimately a production figure in the ERP system.
| Transition | Typical protocols and standards |
|---|---|
| Level 0 ↔ 1 | 4-20 mA, HART, IO-Link, AS-Interface, Profibus, ProfiNET |
| Level 1 ↔ 2 | ProfiNET, IP, Modbus, OPC UA |
| Level 2 ↔ 3 | OPC UA, historian interfaces, MQTT |
| Level 3 ↔ 4 | ISA-95 messages (B2MML), web services, REST APIs |
Edge Computing is increasingly common between levels 1 and 3: an edge device reads data and forwards it to analytics or cloud platforms without every layer in between having to be changed.
🔧 How do you use the pyramid in practice?
The model is most valuable as a framework for inventory, design and security. An approach that recurs in many projects:
- Inventory each level - record which systems, controllers and applications exist. This is also the basis for the asset inventory that NIS2 and the Dutch Cybersecurity Act require in practice.
- Map the data flows - what information moves from level 2 to 3 and from 3 to 4, and which commands flow back?
- Choose standards per transition - for example OPC UA between control and MES, and ISA-95 objects between MES and ERP.
- Group into zones - translate the levels into zones and conduits in line with IEC 62443 and separate IT and OT with a DMZ.
- Assign ownership - who manages which level: OT engineering, IT or operations?
- Record what bypasses the pyramid - direct cloud connections or a Unified Namespace should be designed deliberately, not appear unnoticed.
Example from a Dutch dairy plant: at level 0, temperature and flow sensors measure pasteurisation. At level 1, a PLC controls the heater. At level 2, the operator follows the process in SCADA. At level 3, the MES records the temperature curve per batch for food safety. At level 4, the ERP system books the litres produced and schedules the next order. Mapping it like this shows immediately which interfaces are critical for production and which serve mainly for reporting.
In the pharmaceutical industry the same structure helps define the validation scope under GMP and GAMP: systems at levels 1 to 3 that affect product quality usually fall within it.
🎯 What are the benefits and limitations?
Benefits:
- Shared language between engineering, IT and operations
- Visible responsibilities per level within the OT Architecture
- Basis for segmentation, Defense in Depth and risk analysis
- Support for compliance, because IEC 62443 and ISA-95 use the same level concept
Limitations:
- Rigid interfaces - every new application needs an interface per layer; ten systems that all talk to each other already require 45 point-to-point connections
- Unused data - smart field devices hold diagnostic information that the control system never passes on; NAMUR Open Architecture therefore adds a second channel alongside the pyramid
- Blurring boundaries - Edge Computing, Cloud, AI and the Asset Administration Shell let functions work across levels
Industry 4.0 therefore often replaces the pyramid with a network picture. As a functional and security model, however, the layering remains relevant.
❓ Frequently asked questions
Is the automation pyramid the same as ISA-95?
No, the automation pyramid is an informal model with many variants, whereas ISA-95 (IEC 62264) is an international standard. ISA-95 uses the same levels 0 to 4 but mainly standardises the functions and data exchanged between production (level 3) and business (level 4).
How many levels does the automation pyramid have?
The most widely used automation pyramid has five levels: field, control, supervisory, operations and enterprise. Variants with four or six levels also exist, for example with a separate sensor/actuator level or a cell level.
At which level does a PLC sit?
In the automation pyramid and the Purdue model a PLC sits at level 1, the control level. ISA-95 assigns automated control functionally to level 2, so it is wise to agree within a project which numbering you use.
Has Industry 4.0 made the automation pyramid obsolete?
The automation pyramid is partly obsolete as a data model, because Industry 4.0 and the Unified Namespace let data flow directly between all levels. As a functional model and as a basis for zones in IEC 62443, however, the structure remains useful.
What is the difference between the automation pyramid and the Purdue model?
The automation pyramid is mainly an explanatory and classification model, whereas the Purdue model is a reference architecture from Purdue University. The Purdue model adds level 5 for enterprise IT and level 3.5 for the industrial DMZ and is used mainly for network segmentation.
Where does RAMI 4.0 fit in relation to the automation pyramid?
RAMI 4.0 adopts the levels of IEC 62264 and IEC 61512, which largely match the pyramid, as its hierarchy axis and extends them with Product at the bottom and Connected World at the top. RAMI 4.0 also has an axis for the life cycle and an axis for the IT layers.
📌 In summary
The automation pyramid organises industrial systems from Sensor to ERP into five levels, each with its own function and time scale. It is related to the Purdue Model and ISA-95 but is not a standard. In modern architectures data increasingly flows straight across the layers, while the layering for control and security remains.
The automation pyramid provides structure and oversight within industrial automation, from Sensor to ERP, and is a starting point for IT/OT integration, risk management and digital transformation.