Meinberg IMS-GNS181, Руководство по установке

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4 GNSS Receiver
4.1.1.5 MRS Features
Advanced Source Selection
A firmware V6.24 and the following versions support a mixed combination of reference signals for synchroniza-
tion. In the mixed mode you can select one source only for the ToD (Time of Day) synchronization and another
source for phase and frequency. The phase and frequency can be provided by a highly stable and accurate
source, for example an atomic clock, like Rubidum or Cesium.
The Time of Day (ToD) information represents a “wall clock time” – a specific time with hours, minutes, seconds
and the corresponding date. The ToD information cannot be delivered by an atomic clock alone. Therefore,
if you need the ToD in your system, you need to select one of the reference signal which includes the ToD
information, for example GPS, NTP, PTP, PPS plus string.
If you use the mixed mode the reference clock will be steered first by a reference signal which includes the ToD.
The oscillator will be roughly adjusted until it reaches the highest level of accuracy that can be achieved by
this reference. After that the reference clock switches automatically to a more accurate source, for example a
1PPS coming from an external atomic clock that provides highly stable phase or a 10MHz signal to provide a
stable frequency.
As per default both ToD and Phase are enabled for each available reference source. If you want to use
the mixed mode, then select the ToD for one reference signal and phase for another. The reference sources
you wish to use should be configured first in the Source Priority list. See MRS Settings
→
MRS Source Priority .
Here is one configuration example for Advanced Source Selection:
Figure: An example for a mixed combination of ToD and Phase source for given reference signals.
PTP Min. Clock Class
The MRS system should only use a PTP master to synchronize the clock if the desired clock class is given. It
should be prevented that the slave remains synchronized to a bad master, although another source is available.
IMS-GNS181 Setup Guide Date: 20th March 2020 13