3.10 System clock and
synchronization
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3.10. System clock and synchronization
The internal clock of the device is used to time stamp events
and disturbance recordings.
The system clock should be externally synchronised to get
comparable event time stamps for all the relays in the system.
The synchronizing is based on the difference of the internal
time and the synchronising message or pulse. This deviation is
filtered and the internal time is corrected softly towards a zero
deviation.
Adapting auto adjust
During tens of hours of synchronizing the device will learn its
average error and starts to make small corrections by itself.
The target is that when the next synchronizing message is
received, the deviation is already near zero. Parameters
"AAIntv" and "AvDrft" will show the adapted correction time
interval of this 1 ms auto-adjust function.
Time drift correction without external sync
If any external synchronizing source is not available and the
system clock has a known steady drift, it is possible to roughly
correct the clock error by editing the parameters "AAIntv" and
"AvDrft". The following equation can be used if the previous
"AAIntv" value has been zero.
WeekDriftInOne
AAIntv
8.604
If the auto-adjust interval "AAIntv" has not been zero, but
further trimming is still needed, the following equation can be
used to calculate a new auto-adjust interval.
8.604
1
1
WeekDriftInOne
AAIntv
AAIntv
PREVIOUS
NEW
The term
DriftInOneWeek
/604.8 may be replaced with the
relative drift multiplied by 1000, if some other period than one
week has been used. For example if the drift has been 37
seconds in 14 days, the relative drift is 37*1000/(14*24*3600) =
0.0306 ms/s.
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