Aneroid barometer | Look inside and a little repair

In this video, I put a screw back into a barometer and of course give you a look inside.

[@SloopyJohnG]

The two calibration screws have different functions. The second one, which is available through the rear of the case, is to adjust the static 'zero point' against a single known external value. The smaller screw which you replaced inside the movement adjusts the dynamic calibration. It changes the relative 'gear ratio' between the sensor and the needle, and therefore helps make the instrument read correctly across its whole range, rather than at only one point.