I have had two different brands of thermometers and I would recommend Fermatap's hands down. Seems the best built and most accurate right out of the box. I would install it about 3-4" from the bottom. You want it high enough where it won't get hot from a flame and low enough you can see the temp without the vessel being full. For a 7 gallon pot a 2" probe would be the best length.
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