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Fluid Statics: Manometry





Manometry is the science of measuring pressure with the help of manometers, instruments that utilize columns of liquid. By analyzing the height of these liquid columns, we can determine the pressure being exerted.

How Does it Work?

Imagine a U-shaped tube partially filled with a liquid like mercury or water. One end of the tube is connected to the pressure source (the fluid whose pressure we want to measure), while the other end remains open to the atmosphere.




Here's the magic:

  • The applied pressure forces the liquid in the connected arm to rise.
  • This movement creates an imbalance in the pressure between the two arms.
  • Due to the fundamental principle that pressure equals the product of density, gravity, and height (P = ρgh), the height difference between the liquid columns signifies the pressure difference being measured.

The simple formula to find pressure of fluid using a manometer is to draw a straight line across the U shape at same elevation as shown by the dotted line in the figure.

Pressure at point 1 = Pressure at point 2 


Types of Manometers:

The basic U-tube design paves the way for various manometer configurations, each suited for specific applications:

  • Simple U-tube manometer: Ideal for measuring gauge pressure (pressure relative to atmospheric pressure).
  • Inclined-tube manometer: Amplifies the height difference for low-pressure measurements.
  • Micromanometer: Employs high-precision scales for exceptionally small pressure differences.
  • Differential Manometer: Designed to measure the pressure difference between two points.

Applications of Manometry:

Manometers find applications in various fields:

  • Industrial processes: Monitoring pressure in boilers, pipelines, and hydraulic systems.
  • HVAC systems: Ensuring proper airflow and pressure in heating, ventilation, and air conditioning equipment.
  • Medical field: Measuring blood pressure and other physiological pressures.
  • Environmental monitoring: Studying pressure variations in water bodies and soil.

Advantages of Manometry:

  • Simple and robust design: Easy to operate and maintain.
  • Wide range of pressure measurements: Applicable for various pressure levels.
  • Cost-effective: Relatively inexpensive compared to electronic alternatives


A simple problem is solved below:



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