Data transfer mechanism issues!

[sunny6008]

Hi,

Currently I have PCI-6036E card, Labview 8.0 and DAQmx running on linux.  I will use this system to acquire the voltage output by my sensor. The sample rate will be 1000 Hz. I am a newer to the DAQ and labview. I have some following questions about the data acquisition and transfer mechanism from the FIFO buffer on the DAQ card to system memory.

1. After the sample rate is set by Sample Clock VI and then Start VI is called, can the sample rate be changed? I use the internal clock on the card.  i.e. after the sample rate is set to 1000 Hz, will the DAQ card scan once exactly per 0.001 second? if the application software slows down my computer, will this delay or interrupt the scan process?

2. What is the data transfer mechanism from the FIFO buffer to the system buffer? DMA or interrupt? how can I change this mechanism? And usually how fast is the DMA mode?  If my sample rate is very fast more than 10K Hz, is the DMA mode fast enough to prevent the overflow in the FIFO buffer? And if the buffer is overflow, will the labview report the error?

Thanks!

Chang    

Message Edited by sunny6008 on 05-04-2006 08:27 PM

[devchander]

Find answers in-line with query

1. After the sample rate is set by Sample Clock VI and then Start VI is called, can the sample rate be changed? No it cannot be changed.

Yo have stop, clear current task, reconfigure scan clock vi for new scan rate and start again

I use the internal clock on the card.  i.e. after the sample rate is set to 1000 Hz, will the DAQ card scan once exactly per 0.001 second? Yes it will.

if the application software slows down my computer, will this delay or interrupt the scan process? this depends on your OS, usually buffer overflow error will show up if you lose samples

2. What is the data transfer mechanism from the FIFO buffer to the system buffer? DMA or interrupt? how can I change this mechanism?  

And usually how fast is the DMA mode?  If my sample rate is very fast more than 10K Hz, is the DMA mode fast enough to prevent the overflow in the FIFO buffer?  

read these links

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019O65SAE&l=en-US

http://digital.ni.com/public.nsf/allkb/9723A5096757092D86256E7B004C115C 

And if the buffer is overflow, will the labview report the error? Yes it will, this link might help u

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019KTeSAM&l=en-US