From OpenSCADAWiki
This approach has been identified for several reasons, that is:
- appreciation and excretion the time difference of the data source and the data acquisition PC has no practical purpose other than the diagnostic to detect the very difference in time since the current data is archived in the archive of periodic values, where the time stamp one way or another is drawn and rounded to this periodicity, that is, the part time is more precise for the period of the archive data is lost;
- rarely which data source does have a real-time clock, and when it has something to it immediately the requirement is to synchronize time with an external source of the precision time, which in turn requires solving the difficulties with direct connection of the GPS receiver or access to the NTP server on the Internet or local network; by the definite approach, the precision time is the time of data acquisition PC, even when it is not synchronized itself, since it is one;
- the data source timestamp may change with its own periodicity, or this update may generally be aperiodic, that if this timestamp is used in the acquisition, it will lead to gaps in the archive, and even if the periodicity of the archiving and updating of the source timestamp is the same, such gaps will occur through the lack of synchronization, which will have to be compensated by a decrease in the periodicity of the acquisition and, accordingly, an increase in the load on the network and the source; so this will make the archive little useful, although it is now possible to take such gaps (passable) not by the fact of the absence or the erroneous nature of the data.