My father and I are meteorologist for years. My dad was a meteorologist is the Army Air Corp. We used to build our own instruments. Not unlike the anemometer the Vane also Must Be Balanced for it to work correct. Think about it. If the instrument list to one side then when the wind stops blowing regardless of the last direction it came from the out of balance vane will turn to the down hill heavy direction.
Ambient.... balance your Vanes. It will stop requiring the instrument be so perfectly dead on level during installation.
Thanks for your attention as to this matter // Satman
