Evoked Potential Connection Problem

Thomas Chimento chimento at ursa.arc.nasa.gov
Wed Nov 23 11:16:37 EST 1994


In article <3aoatd$ku2 at brahms.udel.edu>, greggt at brahms.udel.edu (Thomas R. Gregg) writes:
|> In article <94315.113331U12615 at uicvm.uic.edu>,
|> Michael Davis  <U12615 at uicvm.uic.edu> wrote:
|> >I'm going to be recording evoked potentials from the skull surface of
|> >rats.  I have a question concerning the connection between the
|> >electrodes (stainless steel screws) and the amplifiers.  I can do it
|> >by soldering the pins of a connector plug to the screws and cementing
|> >in place, however I was wondering if anyone knew of a way a connection
|> >can be made without the need to solder during surgery.  Is there any
|> >specialized electrode/connector apparatus currently being marketed
|> >for small animal EPs, if so does anyone know the name of it and
|> >the company I could contact?   Thanks for your help.  Mike Davis
|> 
|> Before surgery:
|> 1) Use single stranded (solid) wire with a thin layer of insulation.  
|> California Fine Wire company-- .01 inch diam I think.  Cut a piece of wire
|> 2-3 cm long.  Scrape  4 mm insulation off each end.
|> 2) Solder the underside of the screw head to the length of wire without
|> getting solder on the threads or the top of the screw head- this takes
|> practice. 
|> 3) trim the wire to length and crimp an Amphenol male goldplated
|> connector pin on the free end.  Use a special crimping tool for this.
|> Tom Gregg

Stuff deleted--

Just a mention of a problem caused by soldering a SS screw with lead solder
to a gold connector - dissimilar metals, if contacted by bodily fluids,
i.e., a salty solution, will produce a small battery. This can be a major
source of noise in your recording setup, swamping some preamplifiers. If
the connections are completely encsed in dental acrylic or equivalent,
then you are OK. The problem of dissimilar metals can come up even in
single unit recording with glass microelectrodes if you use a SS needle for
a ground and silver wire in your glass electrode. Personal experience.
Thomas

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