Have a tag:
It pulls from an OPC UA device path and it just counts up "infinitely" (It eventually reaches an integer limit and flips back over to 1 I think?)
I need to be able to have only the count from "today" (so Not the last 24 hours) as its own tag, so I can then do various other bindings as well as historize and reference it in a report.
Most integer "odometer-style" totalizers will roll over to -231. That is, ordinary binary 2's complement.
To display a value for "since X", where "X" is start of day, start of shift, start of hour, or whatever, simply use a scheduled script to read that odometer, and write into a memory tag, at time "X". Then an expression tag that subtracts "value at X" from the current value will be the desired display value. Such an expression would add the rollover span if the result is a large negative number.
If you record the current odometer to your DB at repeatable intervals (more often than X, presumably), you can also answer "how much between Y and Z" with a simple query.
"Scheduled script" as in just an event gateway script?
So, it would just say "value - (value at time)" then system tag write?
What is best / ideal way to query for a value at a specific timestamp in a script.
Also the last paragraph of your response you said you could also do it with a simple query, still through a script or as some kind of value change expression on the tag itself?
Yes, the one where you can specify what time of day (or times) to execute.
No, that script just reads the odometer and writes it directly to a memory tag.
The subtraction (with rollover check) is done in an expression tag.
With just the snapshotting, there isn't. That's why I recommended going further, to writing the odometer to a DB at regular intervals. Then you can query the value at specific times and subtract.
Okay yeah, I would need to "recheck" at regular intervals (though the most ideal would be if it was just "always on") because I need to use the tag in the reporting feature once I can get it to give me a daily count.
I ended up with a script like 30 lines long that just wasn't even functional so not quite sure where to go to actually make this happen but I appreciate your answers.
The snapshot to memory tag + expression tag is only for live display. If you want to make reports, record your snapshots to a DB.
