multi channel acquisition

[Jeff Juzeau]

Hi!

I am using a USB-6211 DAQ-mx board and wish to acquire two signals simultaneously. I  implemented a DAQ-mx input express VI to read simultaneously two different channels, but I wonder if the acquisition on both channels is perfectly simultaneous or if there is a small lag between those (and how much lag, in milliseconds). Is there a setting to check for that ? If I just could get an estimation of the average possible lag, it would be fine (working out something synchronized would be better though!). If there actually is a lag, can I find its value in the specs of the board ?

The acquisition channels are set to analog voltage input and to continuous acquisition.

Thanks!!

[Stuart_G]

Those boards are not simultaneous sampling boards, so I know there is going to be a delay between channels.  You can look at the DAQmx Timing property Timing>>More>>AI convert>>Rate.  This will tell you the rate of the AI convert clock which is how fast each channel is being sampled between sample clocks. 

Hope this helps

StuartG

[Jeff Juzeau]

Well, it says 71428.6...(Hz?). But I am not really clear with what it means! What do you mean by "how fast each channel is being sampled between sample clocks"?

I'm a beginner on Labview, sorry if my questions look stupid !

Thanks
Jeff

[Yardov]

Hi Jeff,

Yes, this is Hz, just take the inverse to know the time (s) between samples.
Here is more information about this convert clock.

Remember, the only stupid question is the one that's never asked
Good luck!