Understand measurement timestamps
Keep UTC, browser-local time and OPC UA timestamps distinct.
Sensor Dashboard documentation. Labels and options depend on the installed software version.
UTC and local display
The gateway clock described in the guide uses UTC. The browser displays local time using its time-zone offset. A difference between these two displays is expected when the local zone is not UTC.
OPC UA source and server times
In the documented system, sourceTimestamp identifies the measurement timestamp and serverTimestamp records when the OPC UA server received the value. Historical reads select records using sourceTimestamp.
| Timestamp | Meaning | Use |
|---|---|---|
| SourceTimestamp | The measurement timestamp displayed in the earlier dashboard; for its wireless arrays, the end of an axis download. | Historical value selection and preserved measurement identity. |
| ServerTimestamp | When the OPC UA server received the value or knew it to be accurate. | Server-receipt context; not a substitute for the measurement timestamp. |
| Relative sample time | Sample index divided by capture sample rate. | Position inside a vibration array; not an absolute UTC timestamp. |
Use the semantics for your measurement type
The earlier guide describes wireless measurement timestamps at the end of an axis download. Preserve the timestamp supplied with the data and check the sensor’s capture semantics before comparing it with another acquisition system.