[CarWiz]

Iron and steel are poor conductors of heat and an air pocket covering the thermocouple inside pipe is even worse. While it will eventually heat, it will degrade the response of you controller. A diamond probe would be best. Silver next best. Since I couldn't afford either, I went with the third best heat conductor and used a copper sleeve to hold the TC to an L-bracket but that will change shortly. A bare TC next to your item is the best location.

I plan to change mine and mount the bare-tip TC on a movable swing arm that I can locate near the item(s) hanging inside. I was about to do this any way to test the temperatures at various locations in the oven. I'm not particularly satisfied with the "convection" design I'm using but the temperature at/near the item is most important. Controller response to temperatures is the next most important.