What is an OPC UA server & how it works in industry

In today's industry, marked by digitalization, automation and the need to make decisions based on real-time data, communication between industrial systems has become a critical factor.

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Machines, PLCs, sensors, SCADA, MES and ERP must exchange information securely, reliably and standardised, regardless of the manufacturer or the technology used. In this context, the OPC UA server has established itself as one of the pillars of modern industrial automation and Industry 4.0.

What is OPC UA, and what is it used for in industry?

OPC UA (OPC Unified Architecture) is an industrial communication standard designed to enable data exchange between heterogeneous systems in an interoperable, secure and scalable way. Its main objective is to eliminate the traditional barriers between devices, software and levels of the industrial pyramid.

An OPC UA server acts as the central point where industrial data is structured, normalised, and exposed so that different clients (SCADA, MES, ERP, cloud applications) can consume it.

PC UA vs OPC Classic: key differences

Before OPC UA, the most widely used standard was OPC Classic (OPC DA, AE, HDA). However, it had significant limitations:

• Dependence on Microsoft technologies (DCOM).

• Poor native security.

• Difficulty in scaling or integrating scaling with cloud and IoT.

OPC UA overcomes these limitations by being:

• Platform independent (Windows, Linux, cloud, embedded).

• Secure from design (encryption, authentication, certificates).

• Adapted to modern and distributed architectures.

Therefore, today, when talking about industrial communications protocols, OPC UA is the standard of reference compared to OPC Classic.

Meaning of OPC and evolution of the standard

OPC originally stood for OLE for Process Control. Over time, the concept evolved into an open standard maintained by the OPC Foundation, focused on industrial interoperability.

The advent of OPC UA brought a paradigm shift: it is no longer just about reading values, but about modelling industrial information, including context, structure, events and history.

What does UA mean in OPC UA?

UA stands for Unified Architecture. This reflects the unification of:

• Data access

• Alarms and events

• History

• Methods and objects

All this under a single coherent architecture, ready to connect plant, management systems and digital platforms.

How does an OPC UA server work?

To understand the value of an OPC UA Server, it is key to know its inner workings and its communication model.

Client-server architecture

OPC UA is based on a client-server architecture:

• OPC UA server exposes industrial data.

• OPC UA clients connect to read, write or subscribe to that data.

A client can be a MES INEXION system, a cloud application or a diagnostic tool. This model makes it possible to completely decouple the source of the data from its consumption, which is essential in complex industrial environments.

Data flow and OPC UA nodes

Data in OPC UA is organised into nodes within an address space. Each node can represent:

• Variables (temperature, state, velocity).

• Objects (machines, lines, sensors)

• Methods (actions or commands)

• Events and alarms

This approach makes it easier for an MES system to receive the industrial context, key to production, quality or efficiency analysis.

What is UA Expert, and how is it used with OPC UA Server?

UA Expert (or OPC UA Expert) is a client tool widely used for:

• Testing OPC UA connections.

• Explore nodes and variables.

• Validate security and certificates.

In industrial projects, UA Expert is often used as a diagnostic tool before integrating the OPC UA server with production systems such as SCADA or MES.

Advantages of using an OPC UA server in your plant

1. Frictionless interoperability. Allows connecting equipment of different brands, from sensors to ERPs, facilitating an open infrastructure.

2. Security by design. Prevents unauthorised access, data manipulation and attacks through encryption and digital certificates.

3. Scalability and future-proofing. From one machine to a complete plant, OPC UA adapts to different levels without the need to change the base architecture.

4. Integration with MES and IoT solutions. An MES such as INEXION can connect directly to the OPC UA server, facilitating real-time data capture, calculation of KPIs (such as OEE), and production traceability without complex integrations.

Industrial use cases

• Production line monitoring: The OPC UA server collects data from sensors and PLCs, which the SCADA and MES visualise and analyse.

• Cloud integration and advanced analytics: Collected data can be sent to IoT or BI platforms for predictive analytics or traceability.

• Remote monitoring and predictive maintenance: By combining OPC Web Server and tools such as UA Expert, machine status can be monitored from outside the plant.

How to implement an OPC UA server step by step

1. Audit your current equipment: Identify if your PLCs or devices are natively compatible with OPC UA or if you need a gateway.

2. Choose the right software: There are commercial and open-source solutions that offer adaptable OPC UA servers.

3. Model the information properly: A good node hierarchy facilitates exploitation by the MES or ERP.

4. Integrate with your MES system: If you already have MES INEXION, the OPC UA integration is direct and allows you to visualize and analyse data in real time, improve decision making and automate the capture of information in the plant.

The OPC UA server is much more than a technical tool; it allows you to connect, standardise, and secure the flow of data from the simplest device to corporate systems. And when combined with the MES INEXION system, the result is a much more efficient, traceable and future-proof operation.

Contact us to implement the MES INEXION system.