OPC-UA – Uniform access to machines and devices on the Internet of Things

Table of Contents

The devices and protocols used are as diverse as the areas of application of the Internet of Things. In the past, this has resulted in isolated solutions. Communication between these solutions is a challenge due to the lack of standards.

OPC and its successor OPC-UA are already widely used in the industrial environment. The myDatanet server has had an OPC version for years. With version 49 the myDatanet OPC-UA server is now available.

ARA Thunersee is the first customer who successfully use the OPC-UA interface. He thankfully provides insights into the project.

What is OPC?

OPC stands for “Open Platform Communications” and is one of the most widespread protocols in the industrial environment. It enables uniform access to a wide range of machines, devices and other systems. OPC is particularly important in the context of Industry 4.0. The standard is managed by the OPC Foundation.

What is OPC-UA?

OPC-UA is the successor for OPC – today also referred to as OPC-Classic. The abbreviation “UA” stands for “Unified Architecture” – the name of the new standard. While OPC-Classis was dependent on basic Windows technologies, OPC-UA is based on TCP/IP and can be used platform-independently.

Unterschied OPC-Classis und CPC-UA
Difference in communication between OPC-Class and OPC-UA

This fixation on the Windows platform was a weakness of OPC-Classic and also limited its distribution on the increasingly growing platforms (e.g. Linux, web, cloud). Therefore, platform independence was one of the primary goals of OPC-UA. The changeover to TCP/IP also has the advantage that communication can now also be routed through standard firewalls, thus enabling better control of communication. OPC-UA has also been further developed in the security area and offers various options for authentication and encryption.

myDatanet OPC-UA Server

Due to the many advantages of OPC-UA, the myDatanet OPC Server has been newly developed for the OPC-UA specification. myDatanet OPC-UA can currently be installed as an application template on every myDatanet appliance, namely every myDatanet instance, and turns an appliance into an OPC-UA Server. No further technical requirements are necessary.

It is planned to also offer the OPC-UA Server as an IoT App in the myDatanet AppCenter in the future.

In the current version, myDatanet OPC-UA supports the OPC-UA-DA and OPC-UA-HA standards for read access in each case.

OPC-UA-DA

The abbreviation “DA” stands for “Data Access” and is the basic function expected from OPC. With DA, individual data points and their value can be accessed. In the case of myDatanet OPC-UA, read access is available for the hist-data and config-data. The last valid value is delivered in each case. The available data points are automatically generated form the settings or the blueprint of a site. This means that no configuration of the data points is necessary.

OPC-UA-HA

The abbreviation “HA” stands for “Historical Access” and makes it possible to read out historical data of a data point. Since historical data is available in myDatanet, myDatanet OPC-UA supports this function. In addition to the data point, the client can transfer a period and receives the appropriate data back.

The OPC-UA standard provides even more possibilities. These include, for example, write access for OPC-UA clients or other specifications such as “Alarms & Conditions”. These are currently not supported by myDatanet OPC-UA.

Authentication

The authentication of OPC-UA Clients is directly linked to the myDatanet user administration. This means that rights management is fully integrated and facilitates security management.

The user used for OPC-UA login has the same rights as via login directly on the myDatanet interface. For example, it is determined which data / site can be accessed. In addition, the user needs the right for API access to use OPC-UA.

Differences to the previous version

In addition to the fundamental conversion from OPC-Classis to OPC-UA (and its resulting advantages such as TCP/IP communication), the new version supports the OPC-UA-HA standard – namely the retrieval of historical data.

OPC-UA is currently limited to read access. The previous version could also write config-data.

USPs of the myDatanet OPC-UA

  • Based on the reliable rapidM2M communication, devices are integrated directly into an industrial environment or into OPC-UA compatible visualisations.
  • The data is transferred once from the device to the server and can then be used multiple times. The data can be viewed on the myDatanet interface queried via the API or displayed in an OPC-UA-based visualisation.
  • Works without adaption with all OPC-UA compatible clients (e.g. Scada systems such as WinCC). The “UaExport” client was used for development and testing.

Best Practice ARA Thunersee

The ARA Thunersee municipal association provides wastewater treatment for 36 Swiss municipalities in the Thun region. 123,000 inhabitants are in the catchment area of ARA Thunersee. ARA Thunersee is one of the most modern wastewater treatment plants in Switzerland and stands out in an international comparison because of its high standard and cost-sensitive operation.

ARA Thunersee was the first to actively adopt the myDatanet OPC-UA interface into its operations. The software “ACRON” from Industrial Automation is used as the OPC-UA client. This software specialises in long-term archiving as well as data evaluation and analysis. ACRON retrieves the data via the myDatanet OPC-UA interface and stores it in its own database. No adaptations on the part of ACRON were necessary to work together with the myDatanet OPC-UA server.

ACRON Konfiguration Clean
Link in the ACRON software with the OPC-UA Server of myDatanet| © ARA Thunersee
Schnittstelle ACRON Clean
Automatic determination of data point in the OPC-UA Client | © ARA Thunersee
Messstellennetz ARA Thunersee
Evaluation of the data in the ACRON software | © ARA Thunersee

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