Where to measure ET on drum roaster I am considering upgrading my home roasting setup to a gas Kaldi Wide. Part of what is so appealing is that this roaster is so bare bones and will be easy to modify to try different things.

I am going to drop a thermocouple into the bean mass to get my bean temp. Beyond that I want to measure the environment temperature as well. Where should I measure that? Somewhere above the drum? As is, this roaster has no forced convection. I am considering adding a duct hose and impeller over the bean hopper with a damper depending on how things go after my first few roasts with no air flow. If I did that would it be more valuable to look at this exhaust temperature? I am under the assumption that the advantage to trying to get an environmental temperature is that it would be more responsive than the actual bean temperature to show you where the roast is going - if I am thinking about it wrong please let me know!
I'm not very familiar with the Kaldi roaster. From what little I've read, most buyers are pretty happy with it. I built a home roaster about a year ago using equipment from RK Drums, which requires a dedicated gas grill. I'm really happy with the results I get from this setup. I noticed the Kaldi also requires the purchase of a gas burner but what size and form is it? I use a single thermocouple that mounts very close (~1/2") to the drum. I'm not sure how you plan to drop one right in the bean mass while the drum is rotating. Again I'm not very familiar with the Kaldi so maybe you've worked this out. Using forced air might help if you think the beans aren't getting even temp distribution. I don't use forced air. The thermal mass of the grill cavity along with the bean rotation seems to distribute the temperate quite evenly. Wherever you place the probe, as long as you can get a consistent and reliable reading you should be able to build your roast profiles accordingly. Good luck and I look forward to your updates with the results!