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OPC UA – the future interface for weighing technology

OPC-UA: SysTec is part of the project group "Specification OPC UA interface weighing technology": Interview with SysTec's Managing Director Rainer Junglas.

The OPC UA interface – background, chances and facts

Interview with Rainer Junglas, SysTec Managing Director

Which requirements are the key elements for the development of a multi-vendor interface?

Growing demands are being imposed on the interfaces between weighing systems and PLCs or ERP systems. Not only the transmission speed and the possibilities of networking with other devices, but also the functional diversity of communication protocols is continuously increasing.

The endeavors within the framework of Industry 4.0 also aim at defining manufacturer-independent interfaces in automation technology so that customers remain flexible. In addition, automation components must automatically identify themselves on the Internet of Things. This will also apply to weighing systems in the future..

That is why the VDMA together with the University of Stuttgart initiated the project 'Specification OPC UA Interface Weighing Technology'. German industrial companies such as SIEMENS and SysTec, as well as the PTB, are participating in order to establish an internationally recognized manufacturer-independent interface for weighing systems. The basis of this standardization is the communication protocol OPC UA (Open Platform Communication - Unified Architecture).

Who will be certifying the OPC UA standards and when can we expect a release?

The so-called OPC Foundation is the neutral industry consortium that certifies OPC UA standards, as -for example- they has already been implemented for CNC machines and robots. At present, the specification we have jointly developed with the OPC Foundation is available for testing, and the official release is expected in 2021.

What protocol is OPC UA based on?

The interface is based on TCP/IP and can use existing Ethernet networks. Initially, this interface does not have real-time capability, but in a later implementation on TSN (Time Sensitive Networking) it can be further developed to a real-time capable solution, which will then require appropriate switches and routers.

What information is transferred with OPC UA?

With the OPC UA weighing technology protocol, the measured weight values are transmitted together with status information of the scale. Commands for zeroing and taring the scale, as known from Ethernet or PROFINET communication protocols, are also standard.

Other commands and parameters differ depending on the application. Specified were automatic scales for single weighing (catchweighers), simple scales (e.g. hopper scales), vehicle scales, continuous scales (e.g. belt weighers and differential loss-in weight scales), automatic filling instruments, counting scales, recipe scales and automatic totalizing scales (receiving / shipping scales). For each of these applications, a separate protocol specification was developed, which is binding for all manufacturers. However, the manufacturer is free to implement additional manufacturer-specific parameters and commands.

What goals can be achieved in weighing technology by using the OPC UA interface?

First of all, the scale operator benefits from the fact that he can exchange weighing systems from different manufacturers with each other or, when networking several weighing systems, use a uniform interface. As soon as the leading manufacturers of ERP systems will offer the OPC UA weighing technology interface, it can be expected that it will be become an item in many inquiries for weighing systems.

In the future expansion stage in TSN networks, it will be possible to replace the functionality of Ethernet and fieldbus networks with a single TSN network, since both, large data packets and time-critical signals can be transmitted via TSN. Both, manufacturers and operators of weighing systems will then equally benefit from this.

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