This is actually my first post but I wanted to say that this forum is awesome and it's already been so useful during my first few cooks. I really appreciate all of the information and helpful support found in the community thus far!
Anyway, I'm having issues with my thermometers. I'm cooking on a Masterbuilt XL 40 gas smoker and I'm using an Ivation dual probe digital thermometer. I did a boil test and found that the digital thermometer is about 2* off and my onboard analog thermometer is 10* off. I'm using the including probe clip and clipping on a grill near the middle of the smoker, directly underneath the rack that I'm using to cook on. It's probably about 4" from the meat.
Here is the problem. I've cooked spare ribs a few times and have used a cook temperature of 275 according to the digital, but the door thermometer reads anywhere from 315-325*. This hasn't been too much of a problem with ribs because I just pull them when they pass the bend test which has been anywhere from 3.5 to 4.5 hours without foiling. When I did a 10 pound brisket, I held at 250* according to the digital, but got to the stall at 165 in roughly 4 hours which seems way too fast. The brisket subsequently came out a bit less moist and tender than I wanted because I suspect it cooked way too fast. I got to 200* in about 7 hours.
Any idea why my probe and door thermometer are ranging anywhere from 30-60* apart despite the fact that they were only 10* apart in the boil test? I've cleaned and re-tested both thermometers and there doesn't seem to be any issues with them.
Thanks in advance!