Real Time clock on cRIO-9074

[smichau]

Hello everybody,

I want to have in my CompactRIO-9074 a precision of 25ms per hour (6.9 ppm). The problem is that the cRIO have a precision of 200 ppm.

My first idea is using a real-time clock (from RS or Farnell for example). But if I use it, which module should I add on the cRIO ?

Nervertheless, maybe, there is module which can keep the good precision on my cRIO without use a real time clock...

Does anybody has an idea...?

Thanks

Simon. M

[nturley]

If I understand you correctly, you want a way to keep accurate time on the controller of your cRIO because the onboard clock has too much drift for your application.  Instead of additional hardware, I think your problem can be solved in software. You can sync up your OS time with an NTP server periodically so that any clock drift will be corrected.  In fact, it looks like you can configure VxWorks targets to do this automatically (http://digital.ni.com/public.nsf/allkb/F2B057C72B537EA2862572D100646D43). If, for some reason, you absolutely cannot get the correct time over the network then you can start looking at timing modules or digital I/O modules that can interface with a third party chip. I believe there's a GPS module that can give extremely accurate timing. But your easiest route is definitely to try to get the time from the network.

Neil Turley
Software Engineer
RIO Software