Mercury barometer. Atmospheric pressure forces mercury up the class tube, which contains a vacuum above the mercury. Pressure is indicated by the height of the mercury column in inches or centimeters (the average surface value is 29.92 inches).

Aneroid barometer. The chamber contains a partial vacuum that expands and contracts for small pressure changes. The linear motion of the chamber is converted into radial motion for display on a dial.

A barograph. As with the thermograph, the drum rotates slowly with time, and the needle records the pressure values with time.

An example of a barograph trace during the passage of a typhoon (hurricane) over Guam. The pressure falls by about 1.5 inches of mercury (~50 hPa) during about a 12 hour period.