How Does a Barometer Measure Air Pressure?
by Guest Writer Jenni Worboys What Is a Barometer? A barometer is a widely used weather instrument that measures atmospheric pressure (also known as air pressure or barometric pressure) – the weight of the air in the atmosphere. There are two main types of barometers – the most widely available and reliable Mercury Barometers, or the newer digital friendly Aneroid Barometer. How does a Barometer Work? The classic mercury barometer is typically a glass tube about 3 feet high with one end open and the other end sealed. The tube is filled with mercury. This glass tube sits upside down in a container, called the reservoir, which also contains mercury. The mercury level in the glass tube falls, creating a vacuum at the top. The first barometer of this type was devised by Evangelista Torricelli in 1643. The barometer works by balancing the weight of mercury in the glass tube against the atmospheric pressure just like a set of scales. If the weight of mercury is less than the atmospheric pres
