Barometers are instruments used to predict short term changes in weather patterns by measuring air pressure. There are two types of barometers: mercury and aneroid.
How do barometers work?
Mercury barometers: Atmospheric pressure balances the column of mercury inside the barometer, the height of which is measured to give air pressure.
Aneroid barometers: An evacuated capsule deflects with changes in atmospheric pressure. Amount of deflection is coupled to and indicating needle.
What is a barograph?
- A barograph is a barometer that records changes in barometric pressure over time. This device usually uses aneroid barometers.
For a more in-depth description of how barometers work, try these sources.