Re: best way to synchronously sample all channels simultaneously

It depends "how simultaneous" you want to be.  It is largely a hardware 
issue.

Most DAQ boards have one A/D converter, and multiplex the input 
channels through it for conversion.  If you are using a really fast 
board, the delay in sampling each channel may be trivial, or it may be 
a big deal - it depends how you set the board up and what its features 
are.  A 1 Ms/sec board would only have a 1 us delay, while a 200ks/sec 
board would have a 5 us delay (at least), etc.

Your other solution is to purchase a truly simultaneously sampling DAQ 
board.  Most DAQ board manufacturers make one, although the price 
usually jumps significantly.  I don't know which ones are supported by 
COMEDI.

NI's cheapest simultaneous sampling board starts at $3K.  Other 
companies (ex., Eagle DAQ) are about half that price.

Feel free to email offline if you want more help -- we've been looking 
at this issue and comparing manufacturer's boards lately.


Robert Butera, Assistant Professor
Laboratory for Neuroengineering
Georgia Institute of Technology, Atlanta, GA USA
http://www.neuro.gatech.edu/~rbutera

Received on 2003-07-09Z14:02:56