11-09-2005 07:26 PM
11-09-2005 07:41 PM
Of course an explanation to go with this subject heading might help
The 6281 M series card samples and fills the buffer like so: 1,2,3 1,2,3 1,2,3 1,2,3 .... It takes one sample from ch0 then moves to ch1 takes and another, then one from ch2, then back to ch0 again.
I need to take 100,000 samples from ch0 then 100,000 from ch2 .... I'm taking data from a high input impedance source and sampling multiple channels at 100kHz. This effective rate (300kHz) implies a 3.3us relaxation time. The 6281 DAQ card needs ~8us to perform well. By taking many samples at a time this ghosting effect can be averaged out.
Anyone know how to pull X samples from one channel then move to the next and repeat? Does anyone know how to do this without stopping and restarting the task?
Win XP / LV 7.1 / PCI-6281 M Series / DAQmx 7.4x
Thanks,
Ab
11-10-2005 11:26 AM
11-10-2005 11:49 AM
11-11-2005 09:27 AM
11-14-2005 08:24 AM
Ab,
I'm not at LV & hardware to test this, but I know a method that used to work under traditional NI-DAQ. There you could specify a channel string similar to "0,0,0,0,1,1,1,1,2,2,2,2" This would perform 12 conversions per sample -- 4 on ch 0, then 4 on ch 1, then 4 on ch 2.
I haven't tried it myself and can't be sure, but I'd expect that a similar trick can be pulled with DAQmx. It may, however, very well be more of a pain to generate and format the channel string.
-Kevin P.
11-14-2005 12:22 PM
11-14-2005 02:09 PM
11-14-2005 05:19 PM