Does a Tag Timestamp reset if overwritten by same value?

[lrose]

Dependent on the type of tag.

In my quick testing, the timestamp was updated for a memory tag, but was not for an OPC tag using IA's OPC connected through the Allen-Bradley Ethernet IP Driver.

I believe that this behavior is an implementation detail of the driver and server, so for instance you may get differing results if you are using IA's OPC server in comparison to using an on-device opc server, or Kepware.

How to Create a Sequence of Events view in Perspective

Keep in mind that the timestamps Ignition gets from an OPC UA server, or generates in its own drivers, is almost always the timestamp of the poll, when the change was detected by OPC, not the actual timestamp when the signal changed in the real device. This means the ordering will be pseudo-random for signals that changed close in time, less than the poll interval. If you really need sequence of events, you must timestamp precisely in the PLC and then buffer transfer to Ignition.