I'm planing to build fuel reserve sensor for my bike with arduino and ntc.
I've found this simple schematic with PIC micro controller: http://dl.dropbox.com/u/15796853/0.GIF
This sensor above works on principle that PIC turn ON/OFF NTC every 30 sec, and checks variations in temperature. So if temp. is rising high, that means that there is no fuel to coll the NTC. And if temperature isn't rising that means that there is fuel in tank which coll down the NTC.
I know how to write code which will turn on/off NTC and I know how to read temp, but what do you think how should interval between two checks be long, and how many difference in % should be between old, and new temp after that interval.
NTC is 100 ohm.