mercury barometers and aneroid barometers both measure air pressure.
Mercury and aneroid barometers.
anaeriod barometer and a mercury barometer
Many do, but not all. Most barometers that people would have in their homes are aneroid barometers, which don't contain any mercury.
Pilots use barometers to see the air pressure from the plane.
They are more portable and can be used for airplane equipment
Digital barometers, much like analog barometers, are used to forecast the weather using humidity, air pressure, and dew point. This answer needed a few more characters.
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predict weather
Mercury
pilots use barometers because they don't want to crash because of the air pressure might be high
To measure pressure.