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4-22
Supporting Functions
857-UM001A-EN-P – July 2009
Table 4.16 – System Clock Parameters (cont.)
Parameter
Value
Dev
±32767
SyOS
±10000.000
AAIntv
±10000
AvDrft
Lead
Lag
FilDev
±125
Set = An editable parameter (password needed).
Astronomically a range –11 ... +12 h would be enough, but for political and geographical
reasons a larger range is needed.
If external synchronization is used this parameter will be set automatically.
Set the DI delay to its minimum and the polarity such that the leading edge is the
synchronizing edge.
Synchronization with DI
Clock can be synchronized by reading minute pulses from digital
inputs, virtual inputs or virtual outputs. Sync source is selected with
SyncDI setting. When rising edge is detected from the selected
input, system clock is adjusted to the nearest minute. Length of
digital input pulse should be at least 50 ms. Delay of the selected
digital input should be set to zero.
Synchronization Correction
If the sync source has a known offset delay, it can be compensated
with SyOS setting. This is useful for compensating hardware delays
or transfer delays of communication protocols. A positive value will
compensate a lagging external sync and communication delays. A
negative value will compensate any leading offset of the external
synch source.
Sync Source
When the device receives new sync message, the sync source display
is updated. If no new sync messages are received within next 1.5
minutes, the device will change to internal sync mode.
Deviation
The time deviation means how much system clock time differs from
sync source time. Time deviation is calculated after receiving new
sync message. The filtered deviation means how much the system
clock was really adjusted. Filtering takes care of small errors in sync
messages.
Unit
Description
ms
Latest time deviation between the
system clock and the received
synchronization
s
Synchronization correction for any
constant error in the synchronizing
source.
s
Adapted auto adjust interval for 1 ms
correction
Adapted average clock drift sign
ms
Filtered synchronization deviation
Note
Set
Set
Set
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