I use a cheap temp guage that I have on the outside of the pipe on my Alaska Stokerstove. It normally stays around 105-110 degrees - cool enough to hold your hand on the pipe. I've had people tell me that that's too cool and somethings wrong but I don't think so. I've been burning this stove for at least 10 years without any problems. Now when its going full blast I get more like 150. I would think it also depends on how big the stove is also - mine is 90,000 btu.
The instructions for my Barometric damper state:
As close as possible to the Stove
Open end of stub should be directed away from wall
Front edge of stub straight up and down - perpendicular to floor.
The opening must be plumb.
I have mine about halfway between the stove and the wall, which is about 2' from the stove, before it enters the chimney. I wouldn't put it directly coming out of the stove.
Hope that helps, Bob.