## Simple Manometers

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# Simple Manometers

A simple manometer consists of a glass tube having one of its ends connected to a point where pressure is to be measured and other end remains open to atmosphere. Common types of simple manometers are:

(1) Piezometer

(2) U-tube Manometers

(3) Single Column Manometers

(1) Piezometer

(2) U-tube Manometers

(3) Single Column Manometers

## (1) Piezometer:

• It is the simplest form of manometer used for measuring gauge pressures.

• One end of this manometer is connected to the point where pressure is to be measured and other end is open of the atmospheres as shown in.

• The rise of liquid gives the pressure head at that point. If at a point A, the height of liquid s h in piezometer tube, the pressure at A

P

• One end of this manometer is connected to the point where pressure is to be measured and other end is open of the atmospheres as shown in.

• The rise of liquid gives the pressure head at that point. If at a point A, the height of liquid s h in piezometer tube, the pressure at A

P

_{A}= ρ x g x h## (2) U-tube Manometer:

• It consists of glass tube bent in U-shape, one end of which is connected to appoint at which pressure is to be measured and other end remains open to the atmosphere as shown in

• 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

Let h

h

S

S

ρ

ρ

As the pressure is the same for the horizontal surface, hence pressure above the horizontal datum line A-A in the lift column and in the right column of U-tube manometer should be same.

For static equilibrium

Pressure above A-A in the left limb = Pressure above A-A in the right limb

P + ρ

P = (ρ

Then

Pressure in the left limb = Pressure in the right limb

ρ

P

For more help in

**(a) For Gauge Pressure (b) For Vacuum Pressure**

• 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

## (a) For Gauge Pressure:

Let A be the point at which pressure is to be measured, whose value is P. The datum line is x-x.Let h

_{1}= Height of light liquid above the datum lineh

_{2}= Height of heavy liquid above the datum lineS

_{1}= Specific gravity of light liquidS

_{2}= Specific gravity of heavy liquidρ

_{1}= Density of light liquidρ

_{2}= Density of heavy liquidAs the pressure is the same for the horizontal surface, hence pressure above the horizontal datum line A-A in the lift column and in the right column of U-tube manometer should be same.

For static equilibrium

Pressure above A-A in the left limb = Pressure above A-A in the right limb

P + ρ

_{1 }g h_{1}= ρ_{2 }g h_{2}P = (ρ

_{2 }g h_{2 - }ρ_{1}x g x h_{1})## (b) For Vacuum Pressure:

For measuring vaccum pressure, the level of the heavy liquid in the manometer will be as shown in.Then

Pressure in the left limb = Pressure in the right limb

ρ

_{2 }g h2 + ρ_{1}x g x h_{1 }+ P_{A}= 0P

_{A}= - (ρ_{2 }g h2 + ρ_{1 }g h_{1)}For more help in

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