Re: The Ideal Filter?

From: N. Thornton (bigcat_at_meeow.co.uk)
Date: 10/12/04 

Date: 12 Oct 2004 07:41:35 -0700

"Ron Hubbard" <hubbard-ron@hotmail.com> wrote in message news:<2t1j7iF1querjU1@uni-berlin.de>...
> Not too long ago I bought a $900 biofeedback machine that I use in
> conjunction with an old IBM Thinkpad laptop. But I found that I had to
> use it in a cold, drafty, room that has no appliances connected to the
> mains in order to avoid 60 Hz electrical noise that ruins the
> brainwave tracings.
>
> Does anyone know of a circuit or a commercial device that
> would *completely* filter out 60 Hz ripple so I could plug my
> laptop's adapter into it without fear of any degree of noise?
>
> Thanks
>
> Ron

Your unit should have a good differential input, clean psu etc, so
this doesnt happen. You wouldnt happen to want to buy another for 900
would you? Only an afternoons work.

The solution really is probably in the design of the unit. Since brain
waves are all below 60Hz it should be poss to mod it with filtering to
at least considerably reduce the problem.

NT