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Manometer

 Manometer

This article covers the definition and description of the manometer, its year of invention, and who invented it. It also discusses the uses of a Manometer, its structure and how manometers work.

A Manometer is defined as an instrument or a device used for measuring the pressure of a liquid. It can also be referred to as a double-legged liquid column gauge used to measure the difference in pressure between two liquids.

The manometer does not only measure the pressure of a liquid. It can also measure the pressure of a gas in a tube. Pressure is the force that a gas or a liquid exerts per unit area. Its weight from gravity contributes to the pressure that a liquid or a gas exerts.

Kinds of Manometer

There are different kinds of Manometers which serve different pressure measurement functions. They can be found more commonly in laboratories and hospitals, although some homes and offices might also have them.

The exact function performed by each manometer is determined by its type and configuration. These factors put together determine each manometer’s different pressure values.

There are different kinds of Manometers specific to measuring different fluid pressures. Each manometer is made and configured to provide values for one particular type of fluid pressure, such as blood pressure, the pressure of a liquid in a tube, etc.

The most common type of manometer is the sphygmomanometer. This manometer is used for measuring and monitoring the blood pressure of patients. This manometer is mainly used by physicians, nurses, and other medical professionals. It is often found in the hospitals where it finds its primary application.

Structure of a Manometer

The structure of a manometer can be described in two terms, a closed-end manometer and an open-end manometer.

The structure of a closed-end manometer is a U-shaped tube having one closed arm and another arm connecting to the gas that is being measured and the nonvolatile liquid (often mercury) in between. The distance between the levels of the liquids in both arms of the tube is proportional to the gas pressure in the container.

The open-end manometer has a similar structure to the closed-end manometer. However, the open-end manometer has one arm of the tube open to the atmosphere. In an open-end manometer, the distance between the liquid levels is proportional to the pressure difference between the gas in the container and the atmosphere.

It is possible to make a simple manometer in the laboratory as its construction is not a difficult one.

Types of Manometer

The manometer is an instrument that detects fluid pressure. Based on several parameters, manometers are divided into distinct categories. They are:

  • U-tube Manometer
  • Enlarged Leg Manometer
  • Well Type Manometer
  • Inclined Tube Manometer

How Does a Manometer Work? 

Manometers function under the principle of hydrostatic equilibrium. This hydrostatic equilibrium indicates that the pressure of any liquid at rest is equal at any point.

Applying this to the U-tube Manometer, the pressure on each side of the U-tube will be equal when both ends of the tube are open to the atmosphere. This means that the liquid level on the right-hand side and that on the left-hand side will be the same. This is a case of equilibrium.

On the other hand, when one end of the U-tube is connected to a gas or liquid supply (i.e., it is not left open) and the other is left open to the atmosphere, there will be an unequal pressure.

Suppose this pressure from the additional gas or liquid supply exceeds the pressure from the atmosphere. In that case, downward pressure will be exerted on the measuring liquid causing the liquid to be pushed down on the side with the greater force and pushed upwards on the side with less pressure.

When the atmospheric pressure is greater than the pressure exerted by the additional liquid or gas supply, the measuring liquid falls on the side open to the atmosphere. It rises on the side connected to the additional gas or liquid supply.

Conclusion

This article clearly explains what a manometer is and its use. It has been established that a Manometer is a simple device that measures pressure differences both in gas and as well between two liquids suspended in a tube.

The principle of operation of a manometer can be summarised with the see-saw concept.

Here, the see-saw is balanced and in equilibrium when carrying equal weights on both sides. However, when the weight is unbalanced by adding greater weight to either side of the see-saw, the see-saw tilts so that the side with the greater weight (greater pressure) is forced downwards. The side with less weight (less pressure) is pushed upwards. This is the summary of the working principle of a Manometer.

Today, there are various manometers, each varying in their specific functions. As stated, the particular function of each manometer is determined by its type and configuration.

Since its invention in 1661, the manometer has undergone various reformations. Today, it has found application in several aspects and several places. Its place of application is determined by its use.