Which Alarm will be notified by a Node?

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federico.guido
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Which Alarm will be notified by a Node?

Post by federico.guido »

Hello

We are implementing a OPC UA alarm client. We can easily subscribe to any node with SubscibeToEvent set to true and receive the alarms.
Each received alarm has a type (custom type) and a condition of course.
Now we would like to know whether there is a way to browse the object model and know upfront which Alarm-type will be notified from that particular object and more important which condition belong to that node.

For example we have 2 node Mixer and Hoven, the alarm condition “cooking temperature too low” will be clearly notified only by the hoven, while “Rotating speed woarning” only by the Mixer.

So far we could only find in the address space the class definition of the alarm and class definition of condition, but nowhere in the object model which alarm and which condition belong to a node.

Is that possible? How?

Thank you

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Support Team
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Re: Which Alarm will be notified by a Node?

Post by Support Team »

Hi,

The root for the event browser hierarchy is the Server object.

HasNotifier references are used from the Server object to other objects with SubscibeToEvent flag set on the EventNotifier attribute. These references are used to build the event notifier hierarchy.

HasEventSource references are used from the event notifier object to the nodes that can be event sources.

HasCondition references are used from notifier or event source nodes to Condition objects.

But it is not required to expose all condition objects in the server address space. Therefore there may be more potential conditions in the server than references from the event notifier hierarchy.

For more details you can download the OPC UA Alarm & Condition specification (Part 9) from here:
https://opcfoundation.org/developer-too ... onditions/
The download is free for everybody.

Chapter 6 AddressSpace organization describes the options in detail and provides examples.

Best Regards,
Unified Automation Support Team

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