In order to create a homeade reflow solder oven, I am using a K-type thermocouple connected through a MAX6675 module and reading it with an ATMEGA8 microcontroller.
When the oven is disconnected from mains, the readings work fine. Through trial and error this lead me to determine that when the thermocouple itself is mounted to the chassis of the oven (which is grounded), the readings are no longer accurate. Obviously I know I can unground the chassis, but I don't really want to do that for safety purposes.
How can I make the thermocouple work while attached to the chassis so I can get proper temperature readings?
I was considering using some RTV silicone to put around the thermocouple intersection point with the frame of the oven, but I wasn't sure this was the best route since I would have to make sure the entire braided metal jacket of the thermocouple doesn't touch the chassis at all.
Also, since I am in the development stage, I haven't tried using the microcontroller without a direct USB serial connection to my computer and as such there are different grounds. Could this be the issue? Will it simply disappear when I move to the stand alone circuit. Thanks!