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Types of Barometers

Used by meteorologists, pilots, sailors and everyday weather enthusiasts, barometers predict weather conditions by measuring atmospheric pressure. While these instruments don't reflect current weather conditions, they do tell you the weather you're likely to see later in the day. Equally functionally when placed inside and outside of your house, barometers come in four different types.

Mercury Barometers
- While mercury barometers are available in various different designs, the standard mercury barometer consists of a vertical glass tube with a column of mercury inside of it. The top end of the glass tube remains sealed while the other end sits in an unsealed reservoir of mercury. This reservoir is known as the cistern. When the atmospheric pressure falls, the mercury column in the glass tube begins to drop, signifying an incoming storm. As the storm passes, the mercury begins to rise as the pressure rises.
Water-based Barometers
- A water-based barometer---also known as a Goethe thermometer---consists of a sealed glass container, which is half filled with water, and a thin spout. This spout connects to the glass container below the water level. When the spout is open, the water fills the spout. When there is low atmospheric pressure, the water level in the spout slowly raises above the water level in the glass container. When the water level in the spout drops, there is high atmospheric pressure.
Aneroid Barometer
- Invented in 1843, the aneroid barometer employs complicated mechanics to read changes in atmospheric pressure. The aneroid barometer consists of a face and a tiny, bendable metal box known as an aneroid capsule or cell. This capsule is made out of an alloy of beryllium and copper. Once the air has been emptied from the box, it is sealed. As the metal box expands or contracts due to outside pressure changes, a series of levers and other devices translates those changes into readings on the face of the barometer.
Barograph
- A type of aneroid barometer, the barograph not only reads changes in atmospheric pressure, but records those pressures over a period of time. Constructed out of a metal cylinder with a pen arm, the barograph reads atmospheric pressure changes like the aneroid barometer while the pen arm produces a continuous reading of those pressure changes on a foil chart or paper. This chart---known as a barogram---allows scientists and meteorologists to study a regions climate, not just one day's weather.

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