cdaq sampling time of 9219 and

[Nenad_Mijatovic]

HI all,

I am troubled by something.  At the moment I am using  4xNI 9219 and 3x9239 AI cards with simultaneous sampling placed in one CDAQ 9172. Basically I need simple scope function with data logging, i.e.. scan all channels and write to txt file. 

I made small while loop and defined all data acquisition with DAQ assistant and included all channels (16 form 9219 and 12 form 9239). In sample clock settings I have entered 5000Hz and I have set 9219 card to be in the ‘High Speed’ mode. Task was set to be in continues mode.

 The result I expected to see in my log file would have each row corresponding to the one sample (or in another words samples are 0.2msec apart for NI9239 channels). For slow 9219 channels, because it can sample fastest at 100 samples /sec , I thought that once sampled value will just be copied 50 times in order to synchronize the 5000 samples /sec. After inspecting the data, I saw only 41 repetition for channels sampled with 9219 module, which means ether the sampling speed is slower then 100S/s or what ….

I am not sure what to make of it, and I need to know what the sampling speed is, in order to correlate sampled data to time.    

PS: I also tried 25kS/s for task sampling speed and instead 250 repeated value I found 203.  

Any help would be great!!!

Thank you in advance.

Regards, Nenad

[Nenad_Mijatovic]

Me again...

It turns out to be faster then 100S/s. If I assume that every sample is 0.2msec (because the task has 5kHz as a sample clock) apart and I have 41 repetitive samples for slow card chanals. That gives = 121.95Hz !? That should not be posible with NI9219 module.

Thanks in advance!.

Regards, Nenad