When setting up a Digital PI tag with a Digital set, what is the best setup of attributes to archive only the state change?
Make the tag as advise tag (Location 3=1 for PI OPC interface) .
From the interface manual :
Advise tags are sent to the OPC interface by the OPC server only when a new value is read into the server’s cache. Scan class 1 is reserved for advise tags, and you can create additional scan classes for advise tags as required. Be sure that the scan rate is fast enough to capture all the changes from the data source.
Compdev and Excdev have no impact on digital tags, you could ignore this attribute while creating the tag.
I usually set compdev & compmin to 0, compmax to 86400 and compression to 1.
The suggestion by Balamurugan Veldurai is the correct one for an OPC Interface. I wanted to add that for an Advise tag, the OPC Interface will sign up for updates with the OPC Server, and the OPC server will send each new value to the interface, at a rate no more frequent than the update rate for the group.
Which software are you using in order to send data to the PI Data Archive?
Retrieving data ...