- From: (unknown charset) Jonathan C Erickson <erickson_at_its.caltech.edu>
- Date: Thu, 25 Mar 2004 13:56:18 -0800 (PST)
hi alex, i am assuing you are using the VIs downloaded from ni.com. yes, it is possible to modify these VIs to gain full control over scan_begin_arg and other parameters that fit within the comedi_cmd structure. it's been some while since i have done this. but if i recall correctly, you first need to modify the VI to accept that argument as an input. then you need to modify the source for the VI CIN, and the VI itself. The source for the CIN should be tucked way back in a directory called lowlevelCIN that you downloaded along with the VIs, the file might be called something like start_cmd.c or something similar. change the appropriate function headers and lines. there should only be a few changes. if it's not obvious what to do, email me back and i'll send over a copy of the source i use the scan_begin_arg controls the timing between successive scans. for instance, say you are sampling channels 1,2,3, and 4 at 1 kHz. Data will be collected at 1kHz for all of these channels--that is, at periods of 1ms, data will be acquired from all of these channels "simultaneously" +/- the A/D conversion time. see the comedi documentation for more on this. alos, i hear there are special function calls for slowly varying signals, but i don't think 1kHz fits under that heading. i've never used slowly varying samples before, so i'm not too knowledgeable about it. hope this info helps. jon On Thu, 25 Mar 2004, Ale[x] Garbino wrote: > I'm using labview to sample several single ended analog inputs, but I'm > unsure of how to deal with noise correction. Is there a way to modifiy > scan_begin_arg within the VI? Also, do this simply increase the time between > scans, or does it measure an 'average' of that scan period as well? My noise > is in the kHz range (I belive most is in 4-24 kHz; from the ignition coils > of the car where the data is being measured); and the signal voltage varies > very slowly; I think a sampling rate of 1 kHz would probably be more > accurate than I need. Is there a way to process the signal with LabView in > this way? > > Thanks, > > A. Garbino > > _________________________________________________________________ > MSN Toolbar provides one-click access to Hotmail from any Web page – FREE > download! http://toolbar.msn.com/go/onm00200413ave/direct/01/ > > > _______________________________________________ > comedi mailing list > comedi_at_comedi.org > https://cvs.comedi.org/cgi-bin/mailman/listinfo/comedi > >
Received on 2004-03-25Z21:56:18