What Is The Main Difference Between Manometer and Barometer

Both barometer and manometer are devices used to measure air pressure. These devices have been in use for many years now, and as a positive consequence of modern and developing technology, today we have a far more advanced devices to measure air pressure, than these simple ones which are very similar in working principle. Even though both devices serve the same purpose, they differ in several properties and design:

A barometer – purpose and characteristics:

The barometer is used for measuring air pressure, but its use is more frequent in areas such as meteorology, for weather forecasting more precisely. The barometer is very useful for weather forecasting as it uses changes in atmospheric pressure to predict the weather. There are two types of barometers: a mercury barometer and an Aneroid barometer. The Aneroid barometer is digital and it's the modern version of the device. The mercury barometer is still in use, and its the earliest version of this device. Back in 1643 by Evangelista Torricelli designed the first barometer which consisted of a simple tall, glass tube filled with mercury. How did this barometer work? According to the change in the atmospheric pressure, the height of the mercury column would change. And as a result of this change, the pressure employed by the mercury column would be equal to the outer, atmospheric pressure exerted on the surface of the tube's reservoir. Mercury barometers are still used today, although many users switch more and more to the digital version of the same, or the Aneroid barometer. After all, mercury is dangerous to work with, and if possible to be avoided it should be.

A manometer – purpose and characteristics:

The manometer is also a device for measuring pressure and also works on the principle of using a liquid to calculate the difference in pressure in the tube and out of it. How a manometer works? The tube of the manometer is in “U” shape and the liquid can be either water or mercury (preferably mercury, since it has higher density and it's easier to calculate). The tube has thin arms on both sides and it's open on both ends for air circulation. The formula to calculate air pressure is as follows:

Pressure (P) = ρ g h

Where, ρ = density; g = acceleration of gravity (9.81 m/s2); h = liquid height .
p and g are known determinants or elements of the formula, while h, or the height of the liquid, needs to be measured. It can easily be measured from the tube, and you have all you need to calculate the pressure. A digital manometer would normally display the result without you needing to do any measurements of your own.

The difference between the two devices:

There are three main points in which the two devices differ:

• Although the barometer is a little simpler than the manometer, it's actually a close-end manometer;
  
• You can't measure other types of pressure with a barometer, except for air pressure. With a manometer you can calculate pressures significantly lower than the atmospheric one;
  
• The design in different :a manometer has two open ends, while a barometer has one end always sealed and on that end has a vacuum attached.  
  

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