Manometer Types

A manometer is a device used for measure the pressure of a fluid by balancing it with against a column of a liquid. Five different types of manometers are shown below with images.

U-Tube Manometer:

It consist a U – shaped bend whose one end is attached to the gauge point ‘A’ and other end is open to the atmosphere. It can measure both positive and negative (suction) pressures. It contains liquid of specific gravity greater than that of a liquid of which the pressure is to be measured.

U-Tube Manometer
where ‘γ’ is Specific weight, ‘P’ is Pressure at A.
Pressure at A isP = γ2h2 – γ1h1

Differential U-Tube Manometer:

A U-Tube manometric liquid heavier than the liquid for which the pressure difference is to be measured and is not immiscible with it.

Differential U tube Manometer
Pressure difference between A and B is given by equation
PA – PB = γ2h2 + γ3h3 – γ1h1

Inverted U-Tube Manometer:

Inverted U-Tube manometer consists of an inverted U – Tube containing a light liquid. This is used to measure the differences of low pressures between two points where where better accuracy is required. It generally consists of an air cock at top of manometric fluid type.

Inverted U-Tube Manometer
Pressure difference can be calculated from equation
P1 – ρ1*g*H1 – ρm*g(H2– H1) = P2 – ρ2*gH2

Micro Manometer:

Micro Manometer is is the modified form of a simple manometer whose one limb is made of larger cross sectional area. It measures very small pressure differences with high precision.

Micro Manometer
Let ‘a’ = area of the tube,
A = area of the reservoir,
h3 = Falling liquid level reservoir,
h2 = Rise of the liquid in the tube,
By conversation of mass we get A*h3 = a*h2
Equating pressure heads at datum we get
P1 = (ρm – ρ1)*gh3 + ρm*gh2 – ρ1*gh1

Inclined Manometer:

Inclined manometer is used for the measurement of small pressures and is to measure more accurately than the vertical tube type manometer. Due to inclination the distance moved by the fluid in manometer is more.
Inclined Manometer
Pressure difference between A and B is give by equation.
inclined manometer equation

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All Comments

  • Can a micromanometer be used for measuring gas pressure ?

    Afzal Oct 15, 2015 4:26 pm Reply
  • Wow…you’ve relieved me of this inverted u-tube confusion I was having. Thanks!

    wilson Mar 28, 2016 3:24 pm Reply

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