Skin galvanic potentials - any info appreciated

[Helena Grbcic]

I am interested in using skin galvnic potentials
to estimate pain perception in humans.  Could someone point me to
the precise method description on how to do it, the good/better/the
best equipment to do it and tell me the plusses and minuses of
this method.

I am also looking for a detailed description of a 
Visual Analog Scale of pain perception or any other pain
perception scales.

I will appreciate any and all answers to this newsgroup and/or 
directly to me at:
goran.pavlakovic at uni-essen.de

Thanks,

Goran