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12:54, EEST
June 5, 2023
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Hi all,
I am here (again) asking for help for a new problem that I have with the Prosys OPC UA simulator. The problem is this:
I am trying to conect with the OPC UA simualtor using a Python script and a client-server-based subscription. I mean, the script contacts with the simulator and it asks for a batch of data each X seconds (for example, 5 seconds) for a specific node (i.e. a variable). However, what I get is that, each 5 seconds, I got the last value of that variable, but not the previous ones. It doesn’t matter if during those 5 second the value has changed each 100 ms. I only get the most recent value. The other ones are… well, I don’t know where they are. Missing in action, I guess đŸ™‚ Curiously, when I repeat the experiment using my own Python-written OPC UA server, everything works perfectly. But when I use the Prosys simulator, it doesn’t.
Do you any idea about what may be the reason behing this weird behaviour?
Best,
Luis
13:31, EEST
April 3, 2012
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Hi,
In OPC UA there are multiple parameters for Subscriptions and MonitoredItems. Did you set a queue size for the MonitoredItem? If not, then it is 1 and thus only the latest value would be sent. If you set it to e.g. 10, then upto 10 last values would be sent when the publish interval happens. Note that anyway in order for you to see any more than 1 value the samplinginterval of the MonitoredItem must be separately set to value lower than the publish interval (the default is typically -1, which means the publish interval is used instead).
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