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  5. QuickOPC-Classic in .NET
  7. Tag Value Trigger
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Tag Value Trigger

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02 Aug 2024 06:47 #12984 by support
Replied by support on topic Tag Value Trigger
Hello.

In your case, you would simply use the subscription mechanism (described in the link you provided), and when the trigger tag value changes to 0, you would then make a read call to retrieve the related value. The subscription does not involve periodic polling.

Best regards

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01 Aug 2024 19:12 #12983 by ChadWilkinson
Tag Value Trigger was created by ChadWilkinson
Hi!

For context:
We have a camera on a production line that is used to validate product codes. This camera reads multiple codes per minute and when the product code is invalid, it changes a PLC tag value to "1" instead of "0" ("1" being invalid and "0" being valid).

Our goal would be to notify the user only when the PLC tag value is "1".

We searched through the documentation and found ways to read the tag value every X amount of time (What we found: opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User%2...OPC%20UA%20Data%20Changes.html). Meanwhile, we would need a trigger that only returns the tag value when it has changed. This is because we want to avoid having a constant communication between the application and the top server.

Would it be possible to implement this, and if so, how? Maybe something that needs to be configured directly in the top server?

Thanks!

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  7. Tag Value Trigger
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