A differential manometer is used to measure: 

Concept:

Differential Manometers:

• Differential manometers are devices used for measuring the difference of pressures between two points in a pipe or in two different pipes.
• A differential manometer consists of a U-tube, containing a heavy or light liquid, whose two ends are connected to the points, whose difference of pressure is to be measured.
• The most common types of differential manometers are

1. U-tube differential manometer
2. Inverted U-tube differential manometer

• The tube generally contains mercury or any other liquid whose specific gravity is greater than the specific gravity of the liquid whose pressure is to be measured.

U-tube differential manometer

• It consists of a U-tube containing a heavy liquid.
• The two ends of the tube are connected to the points whose difference is to be measured.
• It is used for measuring the difference of pressure between two points in the flow section to which it is connected.

Differential inverted U-tube manometer:

• It consists of an inverted U-tube containing a light liquid.
• The two ends of the tube are connected to the points whose difference is to be measured.
• It is used for measuring the difference of pressure between two points in the flow section to which it is connected.
• It is used in two conditions
  • In underground pipeline
  • When the specific gravity of manometric fluid is less than 1