How much does 800xA with AC800M time drift, if time Source signal(GPS) is lost
We have requirement regarding time synchronization, if the time signal receiver is not functioning, then the system time shall drift less than 100 ms per 24 hours.
The configuration is as follows:
All AC800M has “GPS clock1” and “GPS clock2” as SNTP time master.
“ASpectConnectivityServer1” “ASpectConnectivityServer2” also has “GPS clock1” and “GPS clock2” as SNTP time master.
800xA Clients has “ASpectConnectivityServer1” “ASpectConnectivityServer2” as afw time master
Domain Controller1 and Domain Controller2 has “GPS clock1” and “GPS clock2” as SNTP time master.
All other windows nodes has Domain Controller1 and Domain Controller2 as SNTP time master
Can anyone find the manual or explain the maximum a 800xA system with AC800M controllers will drift in time when/if the GPS clocks are powered down/disconnected?
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my answer is not exactly to your question, but might help to solve your problem.
You might consider a GPS synchronized OXCO or rubidium clock as the time sources for your system. These clocks will provide a time according to your requirements while GPS reception is not available. Unfortunately these are not as cheap as GPS clocks.
Yes, it is difficult to say exactly. And it is important to know which drift - between nodes in 800xA or between absolute UTC and 800xA.
Anyhow, 100 ms per 24h for me sounds too optimistic without external clock.
For the details, you can look in 800xA Network Configuration manual - there is a special paragraph about time synchronization.
From my knowledge AC800M has a better stability of the clock than the PC's - in data sheet of the CPU's is written 100 ppm (approx. 1h/year - which gives 9.8sec/day in the ideal conditions)
Especially for the SNTP, the manuals says following:
"The SNTP client implementation in the AC 800M handles some of the known delays. With good SNTP servers, AC 800M can be synchronized with an accuracy better than +/-500 microseconds for nodes connected to the same switch.
The best accuracy is normally achieved with SNTP server usually receives globally synchronized time via a GPS receiver.
The AC 800M controller includes an SNTP server which is always enabled. This server does however not give a very high accuracy."