Adjust Settings for External Variable Polling

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Thomas S.-B.
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Adjust Settings for External Variable Polling

Post by Thomas S.-B. »

Hello,

i have got one question. For our new product we decided to use the OPCUA technology on server and client side..
My part is to implement an OPCUA server and we decided to do that based on your .NET SDK (we are already ordering a license)..

Until I receive the license I started to come into the topic by working through your example code (tutorials on the UA homepage).
My use case will be to communicate with a realtime control (i think example03: reading data from an underlying system).
I already got this running and have now a rough plan to do this..

Today I reached the goal zu communicate with my RealTime Control Mock. So far, so good..

Now my question: I saw now that my OPC UA testclient (UA Expert) receveis the data, but only with a sample intervall of 500ms..
Is it possible to adjust this sample time. And if Yes, How? :-)

Thanks a lot in advance
Best regards Thomas

PS: I am from Austria, so if you prefer we can also communicate in German :-)

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Support Team
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Re: Adjust Settings for External Variable Polling

Post by Support Team »

Hi,

in UaExpert you can adjust the "sampling" and the "publishing" interval for the items in your DAView.
1) Right click on the item (change sampling, because it is per item)
2) Right click on the free space (change publishing, becasue it is per subscription)

Hint: the sampling and the publishing is "requested" by the Client (UaExpert), hence it is more a "wish" than a setting! But it is the Server that returns the "revised" sampling and publish rate (see log window in UaExpert), depending on the minimum/maximum the server wants/is capable of providing data to the clients. The "speed" is controlled by the Server, depending on the load he is capable of handling (and that strongly depends on the implementation of the "real" data source, which is where the server is obtaining the data from).

The revised sampling and publishing rate is meant to be the answer to a wish of the client interpreted as "please not faster than" this rate . The server may give you the data in that rate, or slower (but not faster). The client can protect itself from not being "spammed" with data.
Best regards
Unified Automation Support Team

Thomas S.-B.
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Re: Adjust Settings for External Variable Polling

Post by Thomas S.-B. »

Hi,
thanks a lot for the fast response!

After I sent my request in the forum I saw the possiblity to change the sample intervall in UAExpert.. :-D
So I found in parallel out that sampling is in the hand of the client not in server hands.

Thanks also a lot for the hints. I will have this in my mind when implementing our code.

Best regards
Thomas

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Re: Adjust Settings for External Variable Polling

Post by Support Team »

Hi,

to get this straight, the client is "begging" for something and the server "decides" what is revised. So in my view the "server" has full control, which is good because only the server knows the data source best.

But yes, the client has control within a "range" of sampling/publishing rates. Servers typically have a "list of distinct supported rates", the server will revise the rate "closest" to the request.
Best regards
Unified Automation Support Team

Thomas S.-B.
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Re: Adjust Settings for External Variable Polling

Post by Thomas S.-B. »

Thanks a lot.
During implementation i came now to another question..
Sorry, i thought I write it in that thread instead of opening a new one..

If I have activated the External Polling is it possible somehow to have access on the current data content of another node?
I had a fast look through the examples and webinar code but I could not find that.

Do you have an example for me or could me send a link to the docu? I also had a look on the docu pages but could not find out something.

Thanks again in advance!

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