Is it possible to define a scanclass less than 1 sec? We have OPC-tags, which potentially can send "string" event at a very high frequnecy. How would I be able to get hold of them all?
Yes the OPC interface can have subsecond scan classes. Typically though it is a good idea to use Advised tags so that way the interface is notified of the changes rather than polling and putting strain on the OPC server.
If you do use advised tags, you do not want to have them in the scan class as polled tags, and we typically reserve Scan Class 1 for Advised tags. Generally it is a good idea to have at least one polling value on an interface so that way you can check that value to make sure that the interface maintains a connection to the server.
Just remember that your data acquisition system must poll fast enough to return the data. Depending on your subsystem such as the RTU's and other components, they must all provide the updated information as fast or faster than your scan time.
Lars, here is a KB on performance when using Advise tags concerning group size:
OK, Thanks a lot for your help. Funny dog you've got there "FlowGuy" :-)
Thanks, Boston Terriers are great companions.
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