Share clock PXI

[CBond]

Hi cobayatron,

I'm very happy that this seems to be mostly working for you now, the following is a link to the NI 449X specification document, which is probably more useful for you than the data sheet https://www.ni.com/docs/en-US/bundle/ni-449x-specs/resource/372125f.pdf

[cobayatron]

Hi Cody,

Thanks for the document.

It seems that the deeper I go the less I understand...

Let's see, I manage to avoid errors by using two different reference clocks one for the 4492 module and another for 4330 and 6341 modules but I'm not sure how correct is this since they are working at different rates (PXIe_Clk100 for the latter and PXI_Clk10 for the 4492 module)...

In this situation the difference in the starting time is in the millisecond order of magnitude (which is ok for my requirements). The problem is that when I decrease the sampling rate this difference increases (Was not synchronised??) up to hundreds of milliseconds (for 20 Hz) which is not acceptable. Here, another really strange thing happens: if instead of wiring the number of samples per channel input in the DAQmx READ VI I wire the number of samples per channel input in DAQmx TIMING VI, the acquisition start time is exactly the same for all the modules no matter the sampling rate (the number of samples are now not equal though (???)) I think I could move on but I'm afraif I haven't really understood the issue. I'll try to keep on digging.

[CBond]

Hi cobayatron,

Since this is quite a large and complicated issue, I recommend that you call your local NI support number and they will be able to help you further and possibly consult some of our specialists. 

[cobayatron]

Hi Cody,

I will definitely do so. Anyhow, thanks indeed for all the explanations and your time, it's been a great training.

Best regards,