Pocket barometers are just an alternative to the standard mercury barometers being smaller and lighter. A pocket barometer is similar to the mercury barometer and has all of the same functions as a regular mercury barometer. A good thing about the pocket barometer is that it and can be easily transported wherever needed. On the other hand, the disadvantage of a mercury barometer is that it’s bulky and fragile and makes transportation hard. There are several things that could go wrong with a mercury barometer, things such as the glass tube could easily brake or the mercury might become difficult to read under unsteady conditions such as in a car on the road.
Pocket barometers are based on different principles than the mercury barometers and they’re also known as aneroid barometers because they function without any type of liquid. The aneroid barometers were invented by the French physicist Lucien Vidie in 1843 and are a newer type of barometers. An aneroid barometer is a container that holds a sealed chamber from which some air has been removed, creating a partial vacuum. An elastic disk covering the chamber is connected to a needle or pointer on the surface of the container by a chain, lever, and springs. As atmospheric pressure increases or decreases, the elastic disk contracts or expands, causing the pointer to move accordingly.
Aneroid barometers are even more popular than mercury barometers since they’re based on a newer and safer technology that doesn’t imply mercury which can be if not handled properly hazardous for your health. One of the most popular aneroid barometers is the one shaped like a clock where the barometer pointer moves from left to right in a semicircular motion over a dial, indicating low or high pressure. All of the clock-like aneroid barometers you see hanging on the walls of homes function on these principles. Another type of aneroid barometer has the pointer resting on the side of a rotating cylinder wrapped with graph paper. As the cylinder rotates on its own axis, the pointer makes a tracing on the paper that reflects increases and decreases in pressure. A recording barometer of this design is known as abarograph.
A variation of the pocket barometer is the pocket barometer altimeter also known as a pocket altimeter. The altimeter is a variation of the aneroid barometer and it’s used to measure altitude. This type of altimeters can be found in most modern airplanes and not only.
