2 forum posts
Greetings, I recently obtained an old (like new) Thommen altimeter that uses barometric pressure to calculate altitude. I know there are newer more advanced products on the market, but I liked the looks of it and wanted to give it a try.
I'm hoping that there are a few users here that know something about the use of this older instrument.
I have the manual and have read it, thus I have a basic understanding of the unit. However, I'm a bit confused on how to set up the unit. Would the barometer be set to the local reading? Local airport barometer in my area presently is 30.36. However, I am 25 feet above sea lever and my corrected to mean sea level reading is 30.42". So, would the instrument be set at the local reading, or the calculated MSL reading? It's not easy to calibrate given the very small window and screw in the back of the unit. Also, if I set the barometer to the local reading it would not be dead center at 12:00 o'clock on the face. Would after setting the unit to the local barometric pressure would you move the dial to the known altitude and then use that as a base even though it is not dead center on the dial face?
In any case, any insight or past experience with this unit from other members would be greatly appreciated.