Barometers, manometers and anemometers are all scientific instruments. Scientists use barometers and manometers to measure atmospheric pressure, while anemometers measure wind speed.
A manometer is a tube-like device which measures atmospheric measure. There are two types: closed tube and open tube, but both measure pressure by comparing the pressure exerted by the atmosphere at one end of the tube with a known pressure at the other. Manometer tubes are typically filled with mercury.
Barometers also measure atmospheric pressure. Mercury barometers are a type of closed-tube manometer, while aneroid barometers use a small, spring balance to take the measurement. In the past, mercury barometers were common in family homes where people used them to predict the weather based on the air pressure reading. Rising air pressure meant good weather was on the way, while falling pressure might bring rain.
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Anemometers are a completely different type of instrument used to measure wind speed. There are several different types, but the most common—the cup anemometer—takes the measurement by recording the number of times the wind rotates a fan-shaped device.