OPC UA read data only when it changes

Hi, I want to read data only when it get changes in PLCs.
Anyone have the idea?

Have a look at the "Filter" node. You can set it to only pass a message if the message has changed.

Which type of PLC had been connected?


I am using "Filter" node to read data only when it gets changes in PLCs .

Now I am trying to read data at least one time every hour (even if the data does not change), I did not find a way to do it.

Does someone know how to do it ?

Not at computer right now. But probably a couple of trigger nodes. One set to repeat every hour and one set to rate limit to once per hour.

OPC UA provides monitoring with deadband/absolute filter. Better to use it!

Inside client node, select action: monitor then you have option Deadband with parameters:


Hi there,

in general I would go with the solution provided by @mikakaraila.

Still, there is also a solution by implementing two nodes in parallel. You can use the "filter"-node for the message pass on value change. And in parallel to that another node that lets messages through by each hour (or any other time interval):
For this one might use the delay node, but configured in a way it has the action rate limit and drops intermediate messages:

Togehter the nodes fulfill your use case, I guess.

In Production we're all united! Cheers!

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