@ retrolefty: I was just searching digikey for opamps, but I am a bit overwhelmed by the sheer magnitude of selection. My knowledge of electronics is really limited, so could you pointme to an opamp which might fit my needs, or tell me what I should be looking for?
@ crossroads & everyone else: Sorry that I was not more specific in my first post. The resistors are my own homebrewn things, they are all different, as they are all custom made for slightly different measurements. In theory the one I was testing yesterday should have a nominal resistance of ~ 3000 ohm which should increase to up to about ~ 5000 ohm when subject to maximum force. I dont really have the equipment to test that with me (well, I am sure I could somehow use my arduino, but I dont know how). Somehow nothing makes sense though ... I should be able to get more than a 100mV difference out of that... and I know I had a setup that worked much better... but I dont have that circuit with me...
Current: I dont know. I would not want to overdue that, I assume the material would just melt when heated by too much current. However I have sent 1.6 amps at 9.6volt through it at some point for about a minute and it was fine.
the material I am using: http://www.imagesco.com/sensors/stretch-sensor.html
an image of some readings I got a couple of months ago: http://4.bp.blogspot.com/_GuU3n3DqPBc/TLjQ0yGuFkI/AAAAAAAAAGE/kFxogpc3478/s1600/stretch7.png
(ok, that graph isnt all that informative, but you can see, the resolution is a lot better than the ~20 points which I am getting now.)
Some earlyer results: http://fkeel.blogspot.com/2010/10/getting-better-aquainted-with-stretch.html
I am just really confused and irritated, because I was counting on this to work and cant figure out what I am doing wrong.
Any other ideas would be really appreceated. I will try the millivolts thing now, and I think I will try the opamp as well eventually ... but there must be some other thing I am missing... (ohhh... the idea of combining opamp millivolts and fixing the actual problem suggests a very, very high-res sensor and makes me very happy :-D ..)
about catching soldering irons... I actually did that yesterday. however I did not burn myself badly enough to guarantee that I wont do it again ... but then .. I would not consider myself an engeneer...
Anyway. Thanks for the ideas so far. And if anything else comes to mind I would like to hear it.