OPC UA MonitoredItem Service Set - Filter

[schmidtf]

Hello all,

I was reading through the services that are provided by OPC UA. I was wondering if there is a way to implement filters on a monitoreditem, such as editing it from the tag group? If this is not possible I was wondering if it is on the horizon or there is a reason for not having it.

Thank you very much for your time

[pturmel]

The OPC infrastructure in Ignition is really only exposed to drivers, and drivers have no access to tag groups or other tag properties. (Just pace and OPC Item Path.)

OPC Client connections abstract away the distinctions between internal OPC drivers and external OPC servers, as far as the tag subsystem is concerned.

Please share more about your needs/intentions.

[schmidtf]

My intention is to set a dead band filter for a 3rd party server so that not all tag changes are queued for sending to the client if it doesnt pass the dead band filter. My assumption is that the client would need to be able to set this dead band filter in some manner.

With the goal to limit unnecessary data traversing the network.

[pturmel]

Yeah, not currently possible. But discussed. See this topic:

OPC UA Get node attributes by Node Id

I’ve always wanted to add system.opcua.readAttribute and system.opcua.writeAttribute, but even with its status as something of a wishlist item of mine, it hasn’t been able to claw its way into this world. I think in part because the reality of the implementation is it will be ugly, like the BACnet read/write raw scripting functions, where Milo types have to be injected into the system.opcua namespace so they can be referenced by scripts using these functions, particularly writeAttribute.

The target server would have to publish the nodes to implement the filter.

[Kevin.Herron]

@pturmel

The target server would have to publish the nodes to implement the filter.

That's not quite how it works.

Deadband is one of the things you can configure for each Monitored Item when created: DataChangeFilter – OPC Unified Architecture – Part 4: Services

It's a contract between the OPC UA client and sever, not necessarily anything to do with devices.

We could expose this as a Tag Group property and have all Monitored Items for all tags in that group get created with the same deadband value. It's just not something we're doing, and it wouldn't effect the underlying sampling from that device in any way, just the traffic between client and server.