how to calculate inter channel delay for ni6013

[shubha]

I have a NI 6013.I am using this board to acquire data from 4 channels , with minimum inter channel delay.Inspite of going through the answers on the developers zone i am confused about the caluclation of sampling rate for each channel...
I have 3 questions:
1) What is the minumum interchannel delay possible in NI 6013?.
2)Since i have an acoustic application,I would like to sample at around 20 Khz.
3) Can I use a higher frequency for scanning?

[shubha]

I think i have the answer to my own question. I would appreciate it somone can verify that my analysis is correct.
Since the maximum sampling rate of NI 6013 is 200KS/s,
the minimum interchannel delay will be 5microseconds.
If i want to sample each channel at 20Khz( 50micro seconds), Then the A/D wil sample channel 0,1,2,and 3 at t=0,5,10,15 micro seconds, then wait for 35 microseconds and scan again.
There is no way I can reduce the interchannel delay to be less than 5 micro seconds, and the only way to make the delay insignificant would be to reduce my sampling rate. correct?

[LocalDSP]

You are correct in all your assessments except for the last sentence that should say "the only way to make the delay insignificant would be to increase my sampling rate". The higher the max sample rate of the board, the smaller the inter-channel delay can be.

If you are interested in minimizing (or totally removing) your inter-channel delay, you may want to consider the following. Since you know the value of your delay, you can either correct for it in the frequency domain (if you are doing frequency domain analysis) or even process your signals in the time domain using appropriate filtering. The last technique was described in an NI-Week 2000 presentation. See:

ftp://ftp.ni.com/pub/devzone/pr1h.ppt

Finally, if you choose to correct for the int
er-channel delay in a post-processing operation, it may actually be better to maximize (!) your inter-channel delay in order to minimize inter-channel cross-talk caused by the physical settling time of your board. The AI-Config VI provides an input where you can control the interchannel delay (as a multiple of 5 us in your case) so with 4 channels configured you could enter for example 10 us.

I can send you the LabVIEW software used for the presentation on request. Please email me at amoriat@ni.com