Thermometer anomaly

I purchased two mountable external smoker thermometers: one from BBQ Galore and one from Academy Sporting Goods. I mounted the one from BBQ Galore on my Mini WSM and the other on my WSM lid ( just above the handle). On my first WSM cook since mounting the thermometer I noticed that my factory lid thermometer read about 250 and the Academy thermometer read just above 150. During the cook I removed the Academy and replaced it with the BBQ Galore thermometer. I then began to get readings of 275 on the thermometer I installed vs 250 on the factory lid. Afterwards I rechecked both the Academy and BBQ Galore thermometer in boiling water and they both read just above 200 degrees. Any ideas?

Seems to me that you have three different therms from three different companies and you're trying to match exact temps @ two different locations?
Now I'm Confused

Tim

Haha! Ok let me clarify. I tested two different thermometers in boiling water and came up with identical readings. During a cook I tried both thermometers, one at a time on the same location on my WSM (I had to remove one of them from my mini in order to mount it on the WSM). Although both therms matched in boiling water there was over 100 degree difference when mounted in the same location on the smoker.

I'm glad you took that the right way Dalton. I have no experience with the thermos you listed or the stock WSM one.
Could it be a difference in stem length?

Tim

Tim, I reread my original message and got a little confused myself. The stems are the same length - 3". I'm really puzzled.