Re: Analog Input Board Recommendations

Hi Calin,

I use a NI PCI-6071E board to do 64 channel acquisition, 10kHz per channel, to 
record spike waveforms from neurons. (It's only 12-bit, so it may not be the 
board for you.) While the board specs say it can do 1.25MS/s, implying that 
we could do almost 20kHz/channel, the errors due to finite settling-time 
increase when we go that fast. NI is very straightforward about this point in 
their specs and (with the tiny bit of checking I've done) seem to be accurate 
in their measurement of the errors as a function of scan rate. I certainly 
wouldn't shy away from paying the extra $500 if it turns out to be the better 
board (I don't know if it is, since I haven't tried any MC boards). Compare 
it to the lost labor [& pigs :-)] for corrupt data.

Your signals are well-buffered, right? I've occasionally seen weird things 
with the multiplexer putting junk back on the channel when using e.g. just a 
transistor to buffer signals.

Best,
--Tim

On Wednesday 02 October 2002 10:09 am, Calin A. Culianu wrote:
> Greetings,
>
> I am humbly requesting some advice from you data acquisition and control
> experts out there...
>
> I wanted to ask you guys what would be the best DAQ board for our
> application? (More on the specifics of out application below).  I have
> been perusing the products offered by both Measurement Computing and NI
> and can't decide what to get.  It seems the Measurement Computing boards
> are somewhat cheaper than the NI boards, even though they seem to have
> better specs overall. (higher sampling rates, etc).
>
> However, I know that the multiplexer on a board is often an issue --
> especially if you are sampling from more than one channel at a time.  We
> plan on doing mapping of cardiac tissue, using voltage 'sensors'.  We plan
> on having 64 electrodes map out an 8x8 grid of cardiac tissue in order to
> record cardiac wave propagation on the tissue.  Since 8 * 8 == 64, we
> basically need the ability to sample all 64 channels at once, at a rate of
> 1000 kHz per channel (for an overall rate of 64 kS/s).
>
> Here are the two boards I am looking at:
>
> Measurement Computing --
> PCI-DAS6402/16 High-Speed PCI-bus Compatible, 16-bit, 64-Channel AI.  This
> one publishes a 200kS/s sampling rate, and only costs $1,199.00.
>
> National Instruments --
> NI PCI-6033E 100 kS/s, 16-Bit, 64 Analog Input Multifunction DAQ - This
> one seems to have a lower sampling rate than the above board, but costs
> $1,695, which is about $500 more!
>
>
> Like I mentioned above, sometimes the multiplexer speed is one of the
> unpleasant surprises you get with a cheaper board.  They may say they can
> do 200kS/s, but that might only be for 1 channel.. as soon as you ask the
> multiplexer to switch channels, it's possible that you need to wait a bit
> until the multiplexer settles (in order to avoid ghosting or interference
> from the previous channel), which can drive the overall effective sampling
> rate for 64-channels to something well under 100kS/s -- or even.. *gasp*
> under 64kS/s!! (We had such surprises from the PCI-DAS 1602 board from
> measurement computing).
>
> Has anyone on this list used either boards to do massive 64-channel data
> acquisition?  How happy were you with the overall performance of these
> boards?  Any other boards you can recommend?
>
> Thanks so much for taking the time to read this email and to help,
>
> -Calin
>
>
>
>
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Received on 2002-10-02Z14:40:05