OPC-UA (OPC Unified Architecture) is a vendor-neutral international industrial communication standard (IEC 62541) for exchanging data between plant equipment (PLCs, sensors, machines) and information systems such as the ERP or analytics platforms, with built-in security, semantics and a shared data model.
How OPC-UA works
OPC-UA defines both a transport protocol and an information model. An OPC-UA server (typically the PLC, the machine or a gateway) exposes variables that clients read, write or subscribe to. Each variable carries type, units, hierarchy and metadata, so consumers understand what they are reading without manual mapping tables. Security (authentication, encryption, message signing) is part of the standard, unlike older protocols such as Modbus.
Why it matters for industrial SMEs
For an SME running machines from several vendors, OPC-UA is the cleanest way to unify data capture without proprietary drivers per device. Most modern PLCs ship with an OPC-UA server, and legacy equipment can be exposed through a gateway. That feeds dashboards, OEE calculation or quality systems through one read mechanism, and allows controlled write-back of recipes and setpoints.
Related terms
OPC-UA is a core piece of OT/IT convergence. It coexists with Modbus on legacy equipment and complements MQTT and the Unified Namespace, often processed close to the machine via edge computing. It supersedes classic OPC DA, tied to COM/DCOM on Windows, and underpins sector models such as EUROMAP 77 in plastics injection moulding.