I’ve used a lot of networking technologies over my career. In fact – and I’m not all that happy about this – when I started out in IA (Industrial Automation), it might well have been called INA (Industrial No Automation). Back then, the mechanical guys were kings who ruled over the land of massive bundles of wires linking all kinds of sensors to an old PLC5 (and PLC 2s), and machines viewed as mechanical marvels with gearboxes to transfer power around the machine. (No, I didn’t work at Slate Rock and Gravel with Fred Flintstone – it just seems like it.)
Well, we are now in an era where technologies like EtherNet/IP, PROFINET IO, and Modbus TCP are reaching the end of life. Not that they aren’t useful anymore, but capabilities and requirements for factory floor communications have evolved past them. One of the most interesting new technologies is OPC UA. And one of the most interesting features of that technology is its scalability. A manufacturer can put OPC UA Clients and Servers on infinite-resourced cloud servers, in homegrown and off-the-shelf Enterprise applications, add them to programmable controllers and even embed them into small devices like valves, temperature sensors, and proximity switches. It’s just one of the many reasons that I believe OPC UA is going to be THE technology of the future.
OPC UA provides scalability by grouping capabilities into Profiles. The specific capabilities of an OPC UA Server are described by the Profile it supports. A Profile indicates to other devices (electronically) and to people (human readable form) what specific features of the OPC UA specification are supported. Engineers (or logic) can determine from the Profile if this device is suitable for an application. A Client device can interrogate the Server and determine if it is compatible with the Client and its application and if it should initiate the connection process with the device.
How? An OPC UA Profile is composed of a set of certifiable features termed a Conformance Unit. OPC UA supports a large variety of Conformance Units, and there are tests available for each one. The tests validate that the feature is operating as per the specification. The Profiles, the Conformance Units contained in them, and the required tests are all available on the OPC UA foundation website.
A Profile consists of some subset of all possible Conformance Units. Four OPC UA Profiles are defined in the current OPC UA specification. The Nano Profile is the smallest profile, supporting only the minimum, core functionality required for small, embedded devices with no security. The Micro Profile is more comprehensive. It includes the core Conformance Units present in the Nano, plus subscription services. The Embedded Profile includes even more Conformance Units, while the Standard UA Profile includes the most Conformance Units.
The Nano Profile is one of the profiles supported for OPC UA in Real Time Automation’s source code and gateway products. The Nano Profile identifies the minimum set of functionality needed to implement OPC UA by small, resource-constrained, embedded devices. Though only minimal functionality is supported, OPC UA Client devices are required to support connections to Nano devices, and it provides the basic capabilities to move data from a Nano Server to an OPC UA Client device.
Nano Profile devices are required to include:
- Discovery Services to identify to prospective Clients what capabilities are supported by the Server
- Base Attribute Services to process Read Attribute and Write Attribute from the OPC UA Client
- UA Secure Conversation to implement the basic Secure Conversation protocol but without signing or encrypting the messages
- UA TCP Transport to quickly and efficiently move messages in as few bytes as possible
Some of the functionality that is not found in Nano Profile devices includes:
- Encryption and Signing of Messages to implement end to end security
- Monitored Items to identify variables for subscription services
- Client Server Communications to implement subscriptions to the monitored items
The Nano Profile provides a good combination of OPC UA features and a small size that meets the needs of many industrial automation applications. Still mystified? My book, OPC UA-Unified Architecture: The Everyman’s Guide to OPC UA dives deep into this up and coming technology. For more information on enabling your OPC UA device, contact one of RTA’s application engineers by email at email@example.com or by phone at 800-249-1612.