Absolute timestamp with a cRIO(< 5msec), wich is synched to a NTP synchronized PC

[bela6423]

Hi, I'm doing a project were we want to achieve absolute timestamping relative UTC within 5 msec. Measurements from a hydro power generator must be comparable to measurements on the power grid in different geographical places. The measurement are collected into the DAQ, timestamped and stored to a computer. A GPS watch from Symmetricom with accuracy <40 nsec relative UTC are synchronizing a LAN with NTP version 3. The PC(connected to DAQ and cRIO, available equipment for the project) will be stratum 4 and with an accuracy of 1 msec, due to large distance in the network.

So the PC will always be in sych relative UTC, how du I achieve the timestamp to be synched? Is it possible with the cRIO and DAQ?

I've been reading alot of old threads. One about synchronize the cRIO directly with SNTP. Is it possible to use NTP down to stratum 3 and then synchronize to a stratum 3 server with SNTP? Why can't you use the local clock on the PC to synchronize the cRIO timestamps?

Best regards

Bertil

[Davidek]

Hi Bertil

I had a look around and found this thread, maybe it's the same as you found. I found it pretty comprehensive, but I must say that NTP is not my regular cup of tea. If you sync your computer's clock with the GPS Clock, I think you should be able to setup a server on that computer and use SNTP with the local computers clock as source, but I'm not sure and it's not something I've tried. You will most probably need to use a third party software instead of the windows functionality.

This KB describes how to setup your cRIO to synch with a SNTP server. Just input the computer's IP and make sure you don't have any firewalls that blocks the relevant ports.

Best Regards

David

NISW

[bela6423]

Thanks, I think that's the right way. The hardware I'm going to use are cRIO-9014 with cRIO-9102 as chassis and the software is LabVIEW 8.6. Is the hardware to old for this? I can't see on the specifications that the cRIO got an internal clock to synchronize with the SNTP.

Even though it's real-time hardware, due to delay there's always errors. Is there any good way to be sure(check) that the cRIO is synched to the NTP-server and the timestamps got the right time.

Thanks in advance

Bertil Larsson

[Davidek]

Hi Bertil

The cRIO-9014 is a Real Time Controller, in other words a mini-computer. It has an internal clock, the rest is software. Support for SNTP clock sync was added in LabVIEW Real-Time module 8.6 so as long as you are using that or a later version and your hardware can run it you should be fine. This table shows the mininum version needed and your controller will run using 8.6.

Best Regards

David