Industrial automation has its own technical vocabulary that can be opaque for those approaching the sector for the first time. This glossary brings together the most important terms, explained clearly and with practical context.
Control systems
PLC (Programmable Logic Controller)
Industrial computer designed to control machines and processes in industrial environments. Operates in real time, continuously scanning its inputs (sensors, pushbuttons) and updating its outputs (actuators, motors) according to the loaded programme. Main manufacturers: Siemens, Beckhoff, Rockwell, Schneider and Omron.
DCS (Distributed Control System)
Control architecture designed for complex continuous processes (refineries, chemical plants, power plants). Unlike PLC, the DCS distributes control intelligence across multiple interconnected nodes with high redundancy and ability to manage thousands of regulation loops.
SCADA (Supervisory Control and Data Acquisition)
Software that centralises monitoring and control of industrial processes, collecting data from PLCs and other field devices, displaying them on process screens and saving historical data. Popular platforms: Siemens WinCC, Ignition, Wonderware/AVEVA.
HMI (Human-Machine Interface)
Touchscreen panel or industrial display installed next to the machine that allows the operator to view process status, enter parameters and respond to alarms. Differs from SCADA in that it is local and associated with a specific machine.
BMS (Building Management System)
Centralised automation system for buildings that integrates HVAC, lighting, energy, security and access in a central supervision platform. Main protocols: BACnet, KNX, Modbus.
Fieldbuses and communication protocols
Profinet
Industrial communication protocol based on Ethernet, successor to Profibus. Allows real time (RT) and isochronous real time (IRT) for Motion Control applications. Main field standard for modern Siemens installations.
EtherCAT
Industrial Ethernet protocol developed by Beckhoff. The fastest and most deterministic on the market: 100 µs cycles with nanosecond synchronisation between axes. Especially powerful for Motion Control with many servos.
EtherNet/IP
Industrial protocol over standard Ethernet, developed by Rockwell and managed by ODVA. The reference protocol in the North American market and Rockwell installations.
Modbus TCP/RTU
The world's most widely used industrial communication protocol due to its simplicity and universality. Modbus RTU uses RS-485 (serial), Modbus TCP uses Ethernet. Ideal for simple devices: meters, drives, analysers.
OPC-UA
Modern industrial communication protocol, platform-independent, with built-in security and ability to transport data semantics. The de facto standard for IT/OT communication in Industry 4.0 architectures. See full article: OPC-UA: the Industry 4.0 standard protocol.
BACnet
Building Automation and Control Networks. Standard communication protocol (ASHRAE 135 / ISO 16484-5) for building automation systems (BMS). Enables interoperability between equipment from different manufacturers in HVAC, lighting and energy management.
Components and devices
Variable Speed Drive (VFD / Inverter)
Electronic device that controls the speed of an induction motor by varying the frequency and voltage of the supply. Allows soft starts, variable speed and significant energy savings. Manufacturers: Siemens SINAMICS, ABB ACS, Schneider Altivar, Danfoss.
Remote I/O
Input/output modules installed near sensors and actuators, remote from the control cabinet, communicating with the PLC via a fieldbus (Profinet, EtherCAT, EtherNet/IP). Reduces cabling and facilitates diagnostics. Examples: Siemens ET 200SP, Beckhoff EtherCAT Terminals.
Engineering concepts
OEE (Overall Equipment Effectiveness)
Key productivity indicator that combines: Availability × Performance × Quality. An OEE of 85% is considered world class.
SIL (Safety Integrity Level)
Measure of the reliability of a safety function per IEC 61508 / IEC 62061. Ranges from SIL 1 (least demanding) to SIL 4. Determines the type of hardware, software and validation process required. Safety PLCs (Siemens F-CPU, Beckhoff TwinCAT Safety) are certified for SIL 1-3.
FAT / SAT
Factory Acceptance Test / Site Acceptance Test. Acceptance tests of the control system, FAT at the integrator's premises before shipment and SAT at the client's plant after installation. Documented in a protocol signed by both parties.
CIP / SIP
Clean-in-Place / Sterilize-in-Place. Cleaning and sterilisation systems for process equipment without dismantling. Very widely used in food, brewing and pharmaceutical industry.