Hi,
I don’t think that the NTP server accuracy is the problem.
NTP is designed for “long range time synchronization” and works in a way, that the client has to aquire its time update from the server, and the time interval for aquiring an update changes (it get longer, as longer as the client runs, and it can be up to 1024 seconds between two reqests to the server.
So, even if the server is highly accurate, you’ll not come automatically into the situation that all clients will have the exactly same time in the RTC (as I know, the RTC has a minimum resolution of 1 second).
In addition, the processors base tick (which is the base for the taskclass system) will differ between different PLCs, because it’s not synchronized to a clock.
In distributed processor systems such a synchronisation is normally solved by special “clock synchronize protocols” like IEEE1588, but a such protocol is not available on the PLC.
Can you see in the logger of the clients, that synchronisation really happened (there should be some warning), how is the stratum setting of the NTP server?
Im asking because of the information in that post:
We solved something similar about “synchronized
blinking” some years ago by defining a own mechanism, based on NTP synched clocks (so that they all have the “same second”) + running a timer FB like TON() on every PLC in the same and fast taskclass (for the blink rate) + restarting this timer FB every 4 seconds (based on the RTC’s second modulo 4 information) by setting .enable to False, call the FB, then set it again to True, and so on…
So we “cyclically resynchronized” the starting point of the TON() timer on the different PLCs. Sorry, I can’t remember in detail for example why we’ve choosen 4 seconds for restarting the timer, I have to check if I have something written down somewhere.
Best regards!