Thermal probe

I generally make my own apparatus rather than buy something out of a catalog.

Here i have soldered four thermistors to a piece of CAT5 patch cable. The thermistors have been dipped in plasticoat several times in order to seal the thermistor from the environment. 

The picture shown is the last stage of the dipping. Generally the product works best if allowed to set and then re-dip. Continue this process until the desired coating thickness has been reached. After the product has set up it is chemical and water resistant. It does not have a very high thermal rating. Somewhere near 200f is the maximum operating temperature. This doesn't matter for my application. Not to mention the thermistor i am using is not well suited for temperatures above 180.

A little more about the thermistor. I used an NTC 2.2k ohm nominal 25c thermistor. I have a great deal of experience with this particular make of thermistor and feel quite comfortable with it. I can easily design a data acquisition interface which interpolates r=(t) as well as t=(r). 

Though a thermistor is not as accurate as a properly constructed RTD and Thermocouple it is very economic and exhibits very respectful replication. Replication is the controlling factor therefor i have no doubts with the use of a thermistor for such a project.