Two reports for the same production line can disagree without an arithmetic mistake. Timestamps, sampling, quality flags and period boundaries may differ. Defining these rules before moving data into a report reduces ambiguity later.
What does the timestamp represent?
The time measured at the source differs from arrival time at a server. OPC UA historical access distinguishes source and server timestamps. Specify the report’s timestamp reference, time zone and shift boundaries. Separately define how late data arriving after a connection interruption is assigned to a reporting period.
Do not confuse missing data with zero
Zero production, a missing sample and an invalid measurement are different states. Define how quality flags travel with the data and how calculations use them. Holding the last value may be a display choice, but it must not make an old value look like a fresh measurement. Make incomplete periods visible to report readers.
Reconcile a representative reporting period
Compare field records, the historian and the final report over the same period. Include counter resets, shift changes and communication gaps. Document denominators and units for totals, averages and ratios. Retain an accepted example dataset as a regression check for future report changes.
Review with your team
- Are timestamp reference and time zone defined?
- Is missing data distinct from zero?
- Has a sample period been reconciled to the source?
Next step
To map these points to your plant scope, use the project preparation checklist. An engineering discussion can review installed conditions, open questions and priorities together.
