Tim Wescott <[email protected]> wrote in
news:[email protected]:

> That is my understanding, too. Come to think of it, I'm not sure if it
> would be as much of a case with EEG and polygraph machines, because they
> don't have the same sort of sharp transient embedded in bumps the way
> EKGs do.
>

EEG is much more random than ECG, and you can't really learn as much even
from a perfectly recorded signal. From ECG, things like the width of the
spike (the QRS complex) are critical for understanding of the heart
physiology, as is the time delays between one part of the wave and what
follows.

The useful ECG passband only goes to 250 Hz or so. There are some really
good noise limiting techniques that are often used, like 90dB or more
common-mode rejection amplifiers, and active ground ("driven right leg")
designs. It shouldn't be that tough to get useful analog schemes, as it's
been done for decades on chart recorders (and maybe even kymographs!!). If
I needed to do it accurately and digitally, I'd probably go with a sample
rate of about 4 khz, a nice gentle anti-aliasing filter at about 400 hz,
and maybe some nonlinear smoothing (median filtering and Savitsky-Golay
would both be tested)


--
Scott
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