OPC

OPC, originally “OLE for Process Control” and now commonly “Open Platform Communications,” refers to a family of industrial communication specifications used to exchange data between automation devices, control systems, and IT applications in a vendor‑neutral way.

What OPC is

In industrial and manufacturing environments, OPC commonly refers to a set of standards that define how process data, alarms, events, and historical information are modeled and transferred between:

• Shop floor devices and control systems (PLCs, DCS, CNCs, analyzers)
• SCADA and HMI systems
• Manufacturing Execution Systems (MES) and historians
• Higher-level IT systems such as ERP or analytics platforms

OPC standards specify an interface and data model so that client applications (for example, an MES or historian) can read, write, and subscribe to data exposed by server applications (for example, a PLC gateway or data concentrator) without relying on vendor‑specific protocols.

Main OPC specifications

The term “OPC” can refer to the overall family or to specific generations of the standard:

• OPC Classic: An older group of specifications (such as OPC DA, A&E, HDA) typically based on Microsoft COM/DCOM technology. These are widely deployed in legacy systems but are platform dependent and less flexible for modern architectures.
• OPC UA (Unified Architecture): A newer, platform‑independent specification that unifies and extends the classic models. It adds a richer information model, built‑in security concepts, and support for modern transport mechanisms. OPC UA is the form most often discussed in current OT/IT integration projects.

Operational context in manufacturing

In a plant or regulated manufacturing environment, OPC is typically encountered as:

• An OPC server provided by a gateway, PLC, or dedicated data integration node
• OPC client components built into MES, historian, SCADA, or analytics software
• A standard interface used for aggregating data from heterogeneous equipment for monitoring, electronic batch records, traceability, or quality investigations

Adoption of OPC does not eliminate the need to design, validate, and monitor data flows. Implementations may vary by vendor, and security or data integrity requirements must be addressed by configuration, network design, and operational procedures.

Common confusion

• OPC vs OPC UA: “OPC” is the umbrella term for the whole family. “OPC UA” is the modern, unified architecture version. When someone says “OPC” without qualification, they may mean any of the specifications; context is important.
• OPC vs fieldbus or device protocols: OPC is typically an abstraction layer on top of other industrial protocols (for example, Modbus, Profibus, proprietary PLC protocols). It does not replace those device‑level protocols but provides a standardized way to access the data they carry.
• OPC vs MQTT or other publish/subscribe protocols: MQTT is a transport protocol, while OPC (especially OPC UA) defines both transport options and an information model. They can be used together or independently depending on architecture.

Relation to OPC UA context

OPC UA is part of the OPC family and is often what practitioners mean when discussing modern, secure, and platform‑independent industrial data exchange. In practice, plants may operate a mix of OPC Classic and OPC UA, especially during migration from legacy systems to newer architectures.