Just to get some comparison temps I moved my thermometer above the baro just before the thimble a couple times over the weekend and I noticed a small change in temp. It measured only about 40* less above the baro (about 160*) than below (about 200*). I suspect that because of the location of the baro port I am pulling in warmer air from above the stove which lessens the cooling effect of pulling room air. The flue pipe is angled from the stove to the thimble so the baro is about 8" to the side of the stove, but as you can see from the previous pic, the port for the baro is straight on toward the thimble so I can clean out that pipe more easily. It might pull slightly cooler air if I had it facing toward the right, away from the stove, resulting in a larger temp difference.
The manometer steadily measures between .045 - .05 so there is very little variation in the draft being pulled through the bed of coals as the baro flutters and the below baro temp stays at a steady 200*, maybe dropping to 180* for a short time after loading. The cat-o-mometer's don't seem to notice this slight decrease in temp while in their comatose state in front of the stove - although they do seem to resent the daily disturbances as I load up the stove and empty the ash pan.
Possible entries for our knowledge base...feel free to embellish!
Manometer - a non-living mechanical device that is mounted on the wall in a level position and measures draft pressure
Thermometer - a non-living and mechanical device that is magnetically mounted or inserted and measures temperature on or in the flue pipe
Cat-o-mometer - a living organism that embeds itself and becomes a nearly immovable object in front of the stove for months at a time when outdoor temps drop below 35* . The cat-o-mometer measures room comfort temperature. Checking for a pulse throughout the winter months is a good idea, since a death on their part could be mistaken for their normally comatose behavior.