The pressure of a liquid may be measured by the manometers. These are the devices used for measuring the pressure at a point in a liquid by balancing the column of the liquid by the same or another column of liquid. The manometers are classified as follows:

1. Simple manometers such as piezometer and U-tube manometer.

2. Differential manometer.

A piezometer is the simplest form of manometers used for measuring moderate pressures of liquids.

A manometer is used to measure

1.    High pressure of liquids,

2.    Vacuum pressures, and

3.    Pressure in pipes and channels.

A differential manometer is used to measure difference of pressures between two points in a pipe.