Schau mal hier (google "NTC Resistance"):
http://home.hetnet.nl/~pasopd/pdfs/ntc.pdf
http://www.winbond-usa.com/products/.../APC/ANTMS.pdf
http://www.wuntronic.de/sensors/therm_cald.htm
http://www.wamister.ch/arbeitsbl/Elektrotechnik/NTC.pdf