Multiple DataChange events with no Changed Data|Classic OPC: DA, A&E, HDA, XML-DA, etc.|Forum|OPC Foundation

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Multiple DataChange events with no Changed Data
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andrwe Borne
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05/01/2024 - 08:53
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I am using the OPCAutomation.DLL to create an OPC Client in VB.Net.   Everything works mostly ok, but the issue is I am getting multiple DataChange events firing, but the data never changed.    I am trying to use the signal to do a print, but once in a while I will see multiple dataChange events and will double print. 

 

I can’t attach the Image but the output in VB will look like this:

 

TimeStamp                       Value

——————————————

4/29/2024 6:39:57 PM       True

4/29/2024 6:39:57 PM       True

4/29/2024 6:39:59 PM       False

4/29/2024 6:39:59 PM       False

 

Has anyone encountered this before?   It doesn’t happen constantly, but randomly throughout the day. 

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Randy Armstrong
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05/02/2024 - 20:38
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Looks like you added a VB event handler twice.

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andrwe Borne
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05/16/2024 - 04:54
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I have checked that, but I don’t think so.   The issue only happens a few times a day.   Otherwise it works correctly. 

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Randy Armstrong
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05/16/2024 - 23:20
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With the same timestamp it is likely a bug inside the client process.

Do you see it with more than one server?

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