Engineering · Learn · Plant architecture
The Automation Pyramid
From a proximity sensor on the floor to the ERP in the head office: who talks to whom, and how fast?
A factory runs on layers. Sensors and motors do the physical work. A PLC controls them. A SCADA screen lets operators watch. An MES tracks production. An ERP plans the business. Each layer has its own job, its own speed and its own kind of software. Click a level to highlight it, then test yourself with the sorting game.
This page follows the ISA-95 and Purdue model numbering, level 0 at the bottom. It is a reference model, not a law: modern plants mix levels, and cloud and edge systems blur the lines. For the controller hardware ladder (Arduino to PLC to edge), see Levels of Automation Controllers.
Real-time control stays at the bottom. Operational data moves up. Business decisions come back down as orders and recipes.
Example: a vertical lift module (an automated storage tower) is asked to bring a tray to the picker.
Log scale: each step is a big jump. The bottom of the pyramid thinks in thousandths of a second, the top in weeks and months.
Arduino, ESP32, Raspberry Pi and Jetson are not an official level of the pyramid. Which level they land in depends on the job you give them.
SCADA is not MES
SCADA watches and controls the process now: tags, alarms, trends, operator screens. MES manages the production job: work orders, genealogy, quality, OEE. They share data but answer different questions.
PLC and HMI are different levels
The PLC at L1 runs the machine whether or not anyone is looking. The HMI or SCADA at L2 is where people look and give commands. If the HMI crashes, a well-built machine keeps running safely.
Drives sit on the border
A servo drive or VFD has its own control loops (L1 behaviour) and drives a motor (L0). In drawings, place it by the job it does: a speed loop is control, the motor shaft is field.
Edge and cloud do not replace the PLC
Edge gateways, historians and cloud analytics live at L2 to L4. They read data from the PLC. The control loop stays on the machine, so the line keeps running if the network goes down.
Not every plant has every level
A small workshop may have sensors, a PLC and an HMI, and use Excel instead of MES and ERP. The model still helps: it tells you what each missing layer would do.
Security follows the levels
L0 to L3 is the operations network (OT). L4 and above is the business network (IT). Put a firewall zone between them (called the DMZ, level 3.5) and allow only the traffic you need.
Level numbers follow the Purdue model (0 to 5, with 3.5 as the DMZ) and ISA-95 (0 to 4). Sources differ slightly: ISA-95 groups sensing and control in its lower levels, and some diagrams stack five layers named Field, Control, Supervisory, Planning and Enterprise. Time scales and example products are typical, not fixed rules. Product names belong to their owners and are listed only as examples.