Readout the sampling queue

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user_x
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Readout the sampling queue

Post by user_x »

Hello,
I'm trying to develop an Opc-Ua-Client for a PLC and got some issues there. The PLC is running software from the company B&R.

Currently i want to monitor a single server variable. The value of this server variable is count up every 10ms by 1.

So i want to monitor the server variable with my client, using a subscription. Now i know that the minimal possible publishing interval is 50ms.
The subscription settings include the publishing interval of 50ms, a sampling interval of 10ms for the server and a sampling queue of 100 which the server should use.

At the moment the client only notices every 50ms a value change of 5 from the server variable. --> As far as i unterstand the client only gets the current value of the variable after the publishing time expires.

But what's about the values between this time? Is there a possibility at all to read out the sampling queue? Or how can the sampling queue be used at all? I don't need to see a value change every 10ms with the client, but i want to see 5 sampled values after 50ms. This would be neat for measuring values.



Because english is not my native language feel free to critcize any rude mistakes in my writing. I will correct it then.
Thanks for any responses!

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Re: Readout the sampling queue

Post by Support Team »

Hi,

If you specify a queue size > 1 in the monitored item and you sample faster than the publishing interval, you will get more than one notification per monitored item after a publishing interval.

But it depends on the client API how you get the values.
In our client SDKs, you would get several values for the same monitored item (different values with the same client handle) in one DataChange callback.
Best regards
Unified Automation Support Team

user_x
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Joined: 31 Jan 2017, 11:30

Re: Readout the sampling queue

Post by user_x »

Hi,

Thanks for your reply!

It really looks like the client API I'm using does not support the readout of the queue, if its size is greater than 1, at the moment. I talked to the supplier and they told me to wait a bit for the introduction of this function.

With the UaExpert Client i tested around a lot. The Data Logger View is a good pattern for me to follow later on :)

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