From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-04-10 21:34:41
--- In buildcheapeeg_at_yahoogroups.com, "boid_twitty" <legg_at_magma.ca> wrote:
> I've been reading the spec at
> http://sourceforge.net/projects/openeeg
>
> A sampling frequency of 256 or 200 Hz
> doesn't seem to address 60Hz noise rejection.
> Isn't this an issue?
No, the design uses a an "active-ground", a Driven Right Leg (DRL).
It provides about 40-50dB extra attenuation of common mode signals.
Residual mains hum is easy to remove in software, as long as it
doesn't saturate the amplifiers. A test by Joerg Hansmann indicates
it doesn't. In fact, there was no visible hum at all in his DRL
test. :-)
> After searching posts - 'safety', I get the
> impression that the hardware outlined in the
> spec has been revised, with standard biomedical
> safety issues in mind.
>
> Is there a more recent version of the spec than
> the one appearing on open source forge? Has there
> been a design review?
As in most open source projects... documentation is scarce, but the
important specs are set: There won't be more than 0.5uV noise, and
the input impedance will be around 10Mohms and the resolution will be
either 10 or 12 bits etc. In other words, it will work just fine for
EEG.
We're beyond hardware design reviews for now. Right now the priority
is building and testing. If something needs a redesign and a peer-
review it will be posted here.
> Curious as to why open source site was not used for
> development correspondence posting.
Hmm, not sure. It might be for the 20Mb file area yahoo offers and
general complacency. Yahoo works, doesn't it? :-)
Sure, Source forge has CVS, but it is not as easy to use. I suppose
things will change when the hardware is done and we really need
version control.
Regards,
Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:43 BST