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No notification if no change in OPC value

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26 Jul 2012 09:11 #951 by support
This is a common issue with OPC Data Access, where the OPC Server is required to send updates only if the value or the quality changes. So, if a new value has been truly collected from the device, has a newer timestamp, but precisely the same value, the OPC server typically does not notify its clients. This is per the OPC spec. Some OPC Servers may decide to implement it differently and send all changes, but strictly said that's not compliant with the spec, and there is no way to request such behavior from the OPC client side.

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23 Jul 2012 18:21 #950 by jeancg
exactly, added the ToLocalTime() in eventArgs.Vtq.Timestamp and it worked correctly now.


row["Timestamp"] = (eventArgs.Vtq.Timestamp < (DateTime)SqlDateTime.MinValue)
? (DateTime)SqlDateTime.MinValue
: eventArgs.Vtq.Timestamp.ToLocalTime();

Another thing, I'm following this model using SubscribeMultipleItems to store my values,
I have some variables in my system of sensors that monitor temperature,
it was observing these temperatures does not change in value they are not recorded on the same database setting a scan cycle of 5 minutes to them.
For me this is not interesting because I need to plot a graph with these values even if the values do not change in scan cycles.
Do you have any way to use the method that he SubscribeMultipleItems populate my database even though the values of my tags do not have changes in their values in the scan cycle defined in the method? or would have to use a different method to monitor these temperatures in my database.
Thank you.

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