Where to place temperature probe in fermentation chamber

I am confused, you have 2 sensors?
It is always best to measure the thing you are trying to control.

+1 - We did studies on fermentation temp profiles in college - it’s surprising how much different a fermenting body of wort can vary in temp from inside to outside and from top to bottom.

I do think a plastic bucket allows for more accurate temp reads and more distributed temps when controlling the temp via ambient air temp changes (like a ferm. chamber).

+1 again - what’s the other one for?

I stated what it was for. And again I measure no difference between the fermenting beer and the surrounding air. My tools are calibrated and accurate. I go by what I observe.

If you have circulating air in your chamber, that and the internal convection currents will keep the temperature very consistent throughout the beer.

Sorry, I was confused.  The probe hangs in the air.  And the Thermistor is closed in a vial.  So the “probe” measures the temperature of the air and the thermistor measures the temperature of the inside of the vial?

Fermenting wort produces heat.  Have you ever measured the temperature of the fermenting wort inside the fermenter and compared it with the thermapen’s temperature of the outside of the fermenter?

Yes same results. :o