PCI 6289 Card different sampling rate

[eesen]

I have a PCI 6289 card. Can i adjust different sampling rate for different channel. If not, is there any way to it in my application. Another poin is that can ı read one channel with two "DAQ Read v."
I need this since for one single signal ı need two info; amplitude and frequency. I need amplitude info for every 1 msec and one sample. I need frequency info as far as possible wit multiple sample

[TheWoost]

Hi eesen,

With the PCI-6289, you cannot have different sampling rates for different channels because only one analog input task can be run on the device at a time.  I believe what may work better for your application is to acquire as many samples as you need for your frequency measurement and decimate the  data for obtaining your amplitude measurements.  If you are using the DAQ Assistant and your data is in the dynamic data format, you can use the Sample Compression Express VI to decimate the data with the "Last" option configured.  If your data is not in the dynamic data type, you could use the Decimate (single shot).vi.

Regards,
Andrew W
National Instruments

[eesen]

Can I adjust different sampling rate PCI 6143 card?

[devchander]

Its not possible on PCI 6143 card either

[eesen]

I found I knowledgebase which gives an indirect method to use  different sampling rate.

http://digital.ni.com/public.nsf/websearch/96FD2F4685065C7686256F25006EE8DE?opendocument&Submitted&&...

[TheWoost]

Hi eesen,

While the example program in that KnowledgeBase article does allow you to acquire twice the number of samples for ai1 than ai0 in the same task in the same amount of time, you can't necessarily interleave both arrays of data returned for ai1 and have one array of samples that were acquired at a specific sampling frequency.  To explain this:

Running a test of this VI yielded 2 arrays for ai1, one with a t0 of 10:07:45.9135839 and one with a 10:07:45.9135949.  However, the dt value for both sets is 0.001s.  If these 2 sets of data could be interleaved, you would want the 2nd array to have a t0 of 10:07:45.9140839 (a difference of 0.0005s), but this is not the case because the difference in t0 of each data set is based upon the time for the multiplexer to scan through the channels in the task.

What results when you interleave the data is that samples are not separated by 0.0005s, but instead they are separated by alternating X and 0.001-X where X is the time between channel scans of the multiplexer (in the case of my test, X = 0.000011).  If you plot the interleaved data you would notice that the waveform is very jittery because dt values are not consistent.

Regards,
Andrew W
National Instruments