Hmm... this might work assuming that room humidity affects don't mask th e sensor changes... Humidity sensors are not trivial or cheap... and there is the challenge of long term exposure to the adhesives used in the tape. Also it would be an even bet as to how long the subject would be willing to 'tape' himself up every night. Now that I have said the obviously nasty stuff Yours is an interesting approach in that you postulate a direct approach to the problem at hand. Clearly you spent some time thinking about how to solve the problem. From a technical standpoint yours was a fresh and valid solution. Robert K. Johnson rkj1@ix.netcom.com At 09:21 PM 6/28/99 -0700, you wrote: >if gsr....... can be described as a moisture change.......sweating ..... >why not try a humidity sensor ? > taped on as a patch ? put in different places? >make one as an automatic reference for ambient moisture....auto zeroing the >unit?use a bridge scheme where the resistance varies and upsets the balance >of things.................now in an controlled setting you could put the two >different sensors in one package for testing purposes........there should be >some relationship or trip point............between the two........... >still thinking and long road ahead...................tim > >----- Original Message ----- >From: R. Michael O'Bannon >To: >Sent: Monday, June 28, 1999 5:32 PM >Subject: Re: Help Researching Galvanic Skin Response Circuit Designs > > >> >GSR as an absolute measurement IS a difficult measurement... not looking >> >for absolute ... >> >rather looking for CHANGE in gsr, specifically the change in conductivity >> >caused by sweating >> >I agree about applying dc currents to body, I didn't suggest in any >manner >> >that this was the method to make this measurement (although this is the >> >classic gsr measurement technique) >> >> >> Robert, >> >> I've been thinking about your problem for awhile and perhaps I have a >useful >> idea. You want to detect sweating, not GSR, and this may be an easier >than >> it seems. (I am assuming here that there is actually moisture on the skin >> when these symptoms occur.) >> >> Here is a basic design idea: A small, thin piece of absorbant tissue is >be >> placed on the surface of the skin, then covered with two contacts etched >on >> a very small piece of circuit board. These two layers are securely held >> against the body with a bandage or adhesive tape. >> >> If a small direct current is run through the two contacts, there will be >> almost no current flow if the tissue is dry. Sweat would be absorbed into >> the tissue and conductivity should increase sharply. This assumes that >> there is enough moisture on the skin to saturate the tissue. I would >guess >> it could be made quite sensitive if you place the electrode spacing is >close >> and the tissue thin. The circuitry use could be the type used for rain >> detectors. This has been discussed recently on the list. >> >> Perhaps other on the list can clean this idea up a bit. >> >> Best regards, >> Michael >> >> R. Michael O'Bannon, Ph.D. >> Clinical and Corporate Psychologist >> Atlanta, GA >>