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About Manometers

Manometers are devices that measure pressure. Pressure is measured by the mathematical equation, P = F / A, where P represents the pressure, F is the force, and A is the surface area. For gases, pressure depends on how many gas molecules interact with the walls of the container and the speed with which they travel. In particular, the more molecules there are and the higher their speed, the greater the generated force and the greater the pressure.

  1. The Facts

    • Manometers exist in a variety of designs, but all of them are based on the same common architecture which is a glass tube bent into a U-shape. The glass tube is sealed and filled with mercury. The mercury is responsible for making sure that all air is removed from the sealed end of the tube.

    Function

    • The glass tube of the U-shape manometer is then rotated so that the curved portion is at the bottom and the mercury is allowed to settle. When the mercury settles, a vacuum is produced in the sealed tube. The open tube is then connected to a particular system where pressure is measured.

    Considerations

    • There is no gas to exert force on the mercury, in the sealed tube. However, the gas in the system exerts force on the mercury so that the net result is that the column of the mercury in the sealed tube is higher than that in the unsealed tube. This produces a difference in heights of the columns of mercury and, as a result, is the measure of the pressure of the gas.

    Features

    • The use of manometers in measuring pressure led to the use of millimeters of mercury as the units of pressure. Millimeters of mercury is abbreviated as mm Hg. Another unit that represents pressure is the torr and one torr equals one mm Hg. In other words, one torr of pressure produces one mm in difference in height between the two columns of mercury in a manometer.

    Uses

    • Manometers are useful in everyday life. For example, people use homemade manometers to measure and check the pressure in their propane systems in recreational vehicles. The correct and precise pressure is necessary for the operation of many appliances at their top level of efficiency and performance. According to RVers Corner, a homemade manometer can be built for as little as a few of dollars.

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