jmbj@cbnewsl.ATT.COM (james.m.bittman) (04/25/89)
I'm looking for an inexpensize analog I/O board for the PC bus. What I would Ideally like, (hopefully around $300) 1) 12-bit, 2 channels in and out 2) on board anti-aliasing filters 3) programmable sample rate 4) on-board, (presumably fifo) memory Am I asking for too much, for too little $$$ ? If anyone knows of such a beast please tell me, and I'll post a summary and recommendations if there is interest. Thanks in Advance! Jim Bittman, att!whuts!jmbj
barkdoll@cattell.psych.upenn.edu (Ed Barkdoll) (04/26/89)
In article <487@cbnewsl.ATT.COM> jmbj@cbnewsl.ATT.COM (james.m.bittman) writes: >I'm looking for an inexpensize analog I/O board for the >PC bus. What I would Ideally like, (hopefully around $300) > > 1) 12-bit, 2 channels in and out > 2) on board anti-aliasing filters > 3) programmable sample rate > 4) on-board, (presumably fifo) memory > For some reason A/D boards with a small number of channels, e.g. 2 in/out, are hard to find, or so has been my experience. Metrabyte sells a low speed (30/s) A/D board (DASCON-1) with 4 differential A/D lines in, 2 analog lines out, 12 bits digital I/O lines for $525 (non-programmable). Another board (DAS-16) which _is_ programmable has 12 analog lines in, 2 analog lines out, 8 digital i/o lines and other goodies. It can sample up to 50000/s and costs $999. Data Translation sells a board with 16 single ended 10 bit analog lines in, 2 8-bit analog lines out, 16 lies digital I/O all of which is programmable. the board (DT2808) runs $495. Both MB and DT offer a number of other boards of which these 3 seemed most appropriate. Catalogues can be obtained from the addresses below. As for "anti-aliasing filters" I would suggest that you just make sure that your sampling frequency is twice that of the highest frequency component of your signal - then aliasing will not be a problem. For example if you're only interested in signals < 100 Hz, run your signal through a low freq. band pass filter to remove everything above about 100 Hz and then sample at 200 Hz. If you can't filter your input signal and it contains frequencies greater than 1/2 times your sampling frequency then you're S.O.L because as far as the A/D board is concerned (or any other digital sampling device) an aliased signal and a "true" signal are the same - i.e. they cannot be distinguished. On the other hand if these "high" frequency components of your input signal are of sufficiently low amplitude (which is more or less what filtering your signal ensures) then you won't have to worry about them anyway. Data Translation 100 Locke Drive Marlboro, MA 01752 (617) 481-3700 MetraByte 440 Miles Standish Blvd. Taunton, MA 02780 (508) 880-3000 barkdoll@cattell.psych.upenn.edu