Manometer

What is a manometer?

A Manometer is a scientific instrument used for pressure measurement of liquids and gases.

The U tube manometer is the simplest version of Manometers. A U tube manometer consists of a constant bore glass tube in the form of a long U, partly filled with a suitable liquid such as water, alcohol or mercury. A U tube manometer is shown below.

Figure 5: U Tube Manometer

How to use a U tube manometer to measure pressure

To measure the pressure of a fluid which is less dense and immiscible with the manometer fluid, a connection is made to one limb of the U-tube while a suitable reference pressure is applied to the other limb. The vertical displacement z of the manometer fluid gives an indication of the applied pressure difference Dp. If P_m is the density of the manometric fluid, P_f that of the fluid whose pressure is to be measured and g is the gravitational acceleration, then

Dp = (P_m - P_f)gz

Click here to read about Bourdon Tube for pressure measurement.

A manometer