Of the one specific thermistor I looked I downloaded the excel file and from 0 degree to 100 degree the curve is indeed exponential. I tried to import the data into excel but I've forgotten how to get it to give you a formula to fit the data entered. I browsed a few others and they all look about the same but you can find the math for a precise formula at http://www.epcos.com/web/generator/W...dardizedRT.pdf. Putting that into PBP will be a challenge to say the least.

This site though has a much easier formula if you know a little of your thermistors' data:http://www.mstarlabs.com/sensors/the...libration.html

Though I thought this site gave you a better idea of how to find the right formula:http://www.cantherm.com/products/the...osing_ntc.html