SEPTENTRIO AsteRx-U MARINE Fg, Руководство пользователя

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4.4. HOW TO OUTPUT A PPS SIGNAL
a longer one, the overall signal delay could be increased by say, 20 nsec. If Delay is left
unchanged, the PPS pulse will come 20 ns too late. To re-synchronize the PPS pulse, Delay
should be increased by 20 ns.
By default, PPS pulses are aligned with the satellite time system (TimeSys) as shown in
the
Time Scale fi eld. PPS signals can alternatively be aligned with UTC, local receiver time
(RxClock) or GLONASS time.
When Time Scale is set to anything other than RxClock, the accuracy of the time of the
PPS pulse depends on the age of the last PVT computation. During PVT outages, the PPS
generation time, which is extrapolated from the last available PVT information, may start
to drift. To avoid large biases, the receiver stops outputting the PPS pulse when the last
available PVT is older than the speci
fi ed MaxSyncAge . The MaxSyncAge is ignored when
TimeScale is set to RxClock.
4.4.1 Time synchronisation using the PPS signal
The PPS signal is an electronic pulse synchronised with GPS time clock ticks, it doesn ’ t
itself specify time. To synchronise a device with GPS time, the AsteRx-U MARINE Fg can
be con
fi gured to output both a PPS signal and an NMEA ZDA sentence which contains the
time. The PPS signal arrives fi rst followed by the ZDA whose reported time corresponds to
the leading edge of the PPS signal.
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