Two logs can show different timestamps for the same event because their clocks, time zones, or timestamp definitions differ. Before concluding that a power dip caused a test failure, establish what each recorded time represents and how accurately the records can be aligned.
Keysight’s VSA timestamp-source documentation distinguishes application and instrument sources and separates timestamp resolution from accuracy. Apply that distinction to your test system. Many displayed decimal places do not prove that two independent instruments share an accurate time reference.
Inventory the clocks and event definitions
For each data source, record whether the timestamp marks acquisition start, trigger time, receipt by the computer, result calculation, or database insertion. Include the time zone or time scale and any clock synchronization method. A delayed database write can appear later than an event that physically occurred afterward.
Keep elapsed duration separate from calendar time. Elapsed measurements can be useful for a test sequence even when the wall clock changes, but their relationship to another device’s clock still needs a defined reference.
Perform an alignment check
- Create a safe, observable event that appears in all relevant records.
- Capture it using the normal acquisition and logging path.
- Compare the recorded timestamps and determine the offset.
- Repeat over the time span relevant to the investigation.
- Document the uncertainty or practical limit of the alignment.
Do not assume one fixed offset remains valid indefinitely. Computer sleep, manual clock adjustments, reconnection, or a different acquisition mode can alter the relationship. Recheck after changes that affect the timing path. When merging files from different shifts, preserve the recorded offset from UTC as well as local time; repeated local clock times can otherwise create ambiguous event identities.
Interpret event order within the evidence
| Observation | Appropriate conclusion |
|---|---|
| Events separated well beyond alignment uncertainty | Ordering may be supported by the records |
| Events closer than the alignment capability | Ordering remains unresolved |
| Only database insertion time is available | Acquisition order requires additional evidence |
| Clock source changed mid-run | Analyze the affected segments separately |
Preserve original timestamps when applying an analysis offset. Store the correction and its basis in a separate field so another engineer can reconstruct the comparison. Do not edit raw logs to make events appear synchronized.
Finish the investigation with a statement of the supported timing relationship and its limits. If event order remains uncertain, plan a new capture with a shared observable reference. The failure evidence guide helps protect the other records needed for that next measurement.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist