<pre style="margin: 0em;">I have used both PC's and notebooks with A/D cards,
some from NI and
some from other manufacturers. If you need multiple channel samples,
you have to watch out for inter-channel sampling rate, for which some
cards have larger time intervals than others. The fix then is to get a
simultaneous sample-and-hold, which samples all channels at the time
the first one is sampled (freezing the samples on all the others) and
then fills the multiple channel buffers at a rate faster than the
interval between within channel samples. Noise can be controlled by
using differential input; this provides effective noise cancellation
but cuts the number of available channels in two (typical 8 channel
cards are only 4 channel differential). A/D cards now can sample at
mega-samples per second, but these are often only available in PCI
internal card format. PCMCIA cards continue to improve in
performance.</pre><br>
<pre style="margin: 0em;">I suggest using USB2 or Firewire removable drives
since these are much
faster and larger capacity. The problem with removable disks is that
they generally need more power than a notebook can provide. Also, many
notebooks use low rpm drives -- 4400 or 5400 rpm -- and this slows
their performance. Depending on the notebook, you can replace the
internal disk with a faster and larger one.</pre><br>
<pre style="margin: 0em;">As has been pointed out, many "Sound Cards" have
issues associated
with acquiring signals in the audio spectrum. These issues include
low-frequency drop off, capacitor input (assumes signal is AC), and
other "features" that make audio sound acceptable to our ears but may
alter the basic signal. As a rule, A/D cards make no such compromises;
their job is to record anything from DC to the Nyquist limit of their
sampling rate and induce nothing on the signal amplitude.</pre><br>
<pre style="margin: 0em;">Rugged notebooks are available, but the ruggedness
add thousands of
dollars to the price. These models can take being dropped and immersed
and exposed to dust without much concern. The issue of power remains
an issue. On boats or vehicles you can carry extra batteries. In fixed
spots you can set up solar/battery systems, but when you have to
travel light, then the CF memory recording systems will be the
winner.</pre><br>
<pre style="margin: 0em;">Mike Macaulay
[EMAIL PROTECTED]</pre><br>
<pre style="margin: 0em;">Michael C. Macaulay, Sr. Oceanographer
Applied Physics Laboratory, University of Washington
1013 NE 40th St., Seattle, WA 98105-6698
206-543-7105; FAX 206-543-6785; [EMAIL PROTECTED]</pre><br>
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