Delay between channels

[Sanjeevs]

I use LabVIEW 8.6 and cDAQ 9172 board with 4 NI 9215 modules to acquire 15 channels of data.        All 15 channels acquire data simultaneously for a period of 1 second  @ 4096 samples/ second.     

   Ideally, I need to have all channels perfectly synchronized  (  all 15 channels must acquire the nth sample at exactly the same instant of time).  However, in reality, there will be delays between the channels.    

Hence, please let me know how much of a delay there will be between different channels of data , so that I can incorporate a time correction factor in my Matlab code that processes the  voltage signals acquired  by LabVIEW.  

( For example: after the 5th channel has acquired 2600th voltage sample, how much time elapses before the 6th channel acquires the 2600th voltage sample?  ) 

Thanks 

[Christian Mergl]

Hey,

I think the following KB might help you:

http://digital.ni.com/public.nsf/allkb/CAE12AA9BCAA51A48625722C004866F8?OpenDocument

Christian

[Christian Mergl]

I was to late to edit the message.

the posted KB is only for Sigma/Delta Converter Modules which have their own timebase.

Your 9215 works with the AI Sample Clock which means all your modules are working with the same timebase from the cDAQ chassis.

Can you please shed some light on how you determine the channel delay?

Did you connect the same sinewave to every channel and compare the signals?

Thanks,

Christian

[KyleBryson]

Hi Sanjeevs,

As the NI 9215 is a simultaneous sampling module, there is no delay between acquisitions of different channels in the same sample, as there would be on multiplexed hardware.  While there is some uncertainty possible between sampling different channels/modules in your system, it should be extremely small relative to your sampling rate. (<< 1 microsecond)

Regards,
Kyle