Doug Knowles knowled at ccsmtp.ccf.org
Wed Aug 18 08:57:26 EST 1993

In article <24otu4$q5e at male.EBay.Sun.COM> andrewb at europe.EBay.Sun.COM writes:

>It's also possible to build your own set-up.  With any descent personal
>computer or workstation, a multi-channel D/A board, a high-grade multi-channel
>amplifier, and some software, you can set up your own system.  The advantages
>are price and flexibility (the computer and D/A board aren't "dedicated" to
>EEG recording, as they are in the "package" systems).  Disadvantages
>are: you need to know more about what you're doing (not necessarily a 
>disadvantage :-) and you need the software.  I'm not sure what's availible
>commercially, but you could ask around about it.  If you go this route,
>you'll still need to contact Nicolet or some other electro-phys company
>to get the electrodes and electrode paste.
>A possible source for D/A boards:  (NOTE: some boards already have adequate
>amplifiers buit-in- just add electrodes!  You can figure out if an amp
>is adequate by calculating your expected signal strength, desired resolution,
>and desired range then comparing to the bord's specs.)

I strongly caution you to be very careful when planning to use 
homemade or general purpose amplifiers for human use.  SAFETY of the
subjects must be the primary consideration. (You also fail to mention
consideration of noise levels, bandpass filters, and calibrations.)
Human-use rated amplifiers are carefully designed to provide proper
isolation from ground and to avoid passing current through the 
patient, even in the event of electrical component failure within the
amplifier.  Grounding is a complex subject that must be carefully 
considered in order to eliminate noise (especially 60 Hz) while
maintaining subject safety.
Starting references:  

Epstein, Charles M. (1993) Technical aspects of EEG: An overview,
in: _The_Treatment_of_Epilepsy:_Principles_and_Practices_, edited by
Elaine Wyllie, Lea & Fibiger, Philadelphia, pp. 202-210

Seaba, P. (1980) Electrical safety, _Am._J._EEG_Technol._ 20:1-13.

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