In this post, you will learn what is Manometer and how it works with It’s Working principle, Applications, Advantages, Types of Manometers and more
Manometer and It’s Types
The manometer is a device used to measure pressure at a point in a fluid by balancing the column of fluid by the same or another fluid.
Following are the three different types of manometers:
- Simple manometers
- Differential manometers
A simple manometer has a glass tube that’s one end is connected to a point where pressure is to be measured and the other end remains open to atmosphere.
Common types of simple manometers are:
- U-tube manometer
- For gauge pressure
- For vacuum pressure
- Single Column Manometer
- Inclined tube manometer or Sensitive Manometer
For measuring the pressure inside a vessel or pipe in which liquid is there, a tube is attached to the walls of the container or pipe in which the liquid remains so liquid can rise in the tube. By determining the height to which liquid rises and using the relation p = ρgh, a gauge pressure of the liquid can be determined.
Such a device is known as Piezometer. To avoid capillary forces, a piezometer tube has to be about 1/2 inch or more. It is essential that the opening of the instrument to be tangential to any fluid motion, otherwise an incorrect reading will result.
2. U-tube Manometer
As shown in the figure it consists of a glass tube bent in V-shape, with one end is connected to a point at which pressure is to be measured and the other end remains open to the atmosphere.
The tube carries mercury or any other liquid or fluid whose specific gravity is much higher than the specific gravity of the liquid whose pressure is to be measured.
- For gauge pressure
- For vacuum pressure
3. Single Column Manometer
Consider a vertical tube micromanometer connected to a pipe containing light liquid under very high pressure. The pressure in the pipe will force the lighter liquid in the basin to push the heavier liquid downwards.
Due to the larger area of the basin, the fall of a heavy liquid level will be very small. This downward movement of heavy liquid into the basin will result in a significant rise of heavy liquid in the right limb.
4. Inclined Tube Manometer
If the vertical tube of the micromanometer is made inclined as shown in figure then it is called inclined tube micromanometer.
This type of inclined micromanometer is more sensitive than the vertical tube type. Due to inclination, the distance moved by the heavy liquid in the right limb is comparatively more. Thus it can give a higher reading for the given pressure.
Read also: What are the Applications of Pascal’s Law?
The differential manometer is a device used to measure the pressure difference between two points in a pipe or in two different pipes.
A differential manometer consists of a U-tube, containing a heavy liquid, with two ends connected by points whose pressure difference is to be measured:
Types of differential manometers are:
- Two piezometer manometer
- U-tube differential manometer
- Inverted differential manometer
1. Two Piezometer Manometer
It consists of two piezometers mounted at two different gauge points where the pressure difference is to be measured. The pressure difference between two points can be simply measured by the difference in the level of liquid between the two tubes. It possesses some limitations in the form of piezometers.
2. U-tube Differential Manometer
It is a device that is used to measure the pressure difference between two points in a pipe or between two different pipes. this manometer is consists of a U shaped tube containing a heavy liquid.
The two ends are connected to the two desired points in the pipe whose difference of pressure is required. Let pressure at point A be more than at point B. Then the greater pressure at A will force the heavy liquid in U-tube to move downwards. This downwards movement of the heavy liquid in the left limb will cause a corresponding rise of the heavy liquid in the right limb.
3. Inverted Differential Manometer
In this type of manometer, the U-tube is inverted and contains a light liquid. The two ends of the tube are connected to the points whose pressure difference is to be measured.
It is used for measuring the difference in low pressures. The figure shows an inverted U-tube a differential manometer connected to the two points A and B. Let the pressure at point A is more than the pressure at point B.
Advantages of Manometers
Following are the main advantages of manometer:
- It is simple to construct.
- It has great accuracy.
- Used to measure pressure, temperature, flow and other process variables.
Disadvantages of Manometers
Following are the main disadvantages of manometer:
- The manometer has a smaller dynamic response.
- They are fragile and therefore provide low portability.
- They have small operational limits which are on the order of 1000 kN/m2.
- The density of manometric fluid depends on temperature. Therefore errors may occur due to change in temperature.
Application of Manometers
Following are the main application of manometer:
- Used in the maintenance of heating, ventilation and air conditioning (HVAC) systems, and gas systems.
- It is used to construct bridges, swimming pools and other engineering purposes.
- Used in climate forecasting.
- In clinical applications such as blood pressure measuring and physiotherapy.
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