In the case where the OPC UA Serversubscribes to a value from another OPC UA Server, each Serverapplies its own serverTimestamp. This is in contrast to the sourceTimestampin which only the originator of the data is allowed to apply the sourceTimestamp.
If the Serversubscribes to the value from another Serverevery ten seconds and the value changes, then the serverTimestampis updated each time a new value is received. If the value does not change, then new values will not be received on the Subscription. However, in the absence of errors, the receiving Serverapplies a new serverTimestampevery ten seconds because not receiving a value means that the value has not changed. Thus, the serverTimestampreflects the time at which the Serverknew the value to be accurate.
- the device is checking values every 0,5 seconds,
- the connection to the device is good,
- the device sent an update 3 minutes ago with a value of 1,234.