Pressure difference can be measured using a manometer. Different kinds of manometers are available. A U-tube manometer (Figure 2.6) uses a secondary fluid such as mercury, water or non-volatile oil. Each limb of the manometer is exposed to either or . When the liquid levels reach equilibrium, velocity is calculated as
can be measured using a manometer. Different kinds of manometers are available. A U-tube manometer (Figure 2.6) uses a secondary fluid such as mercury, water or non-volatile oil. Each limb of the manometer is exposed to either 
or 
. When the liquid levels reach equilibrium, velocity is calculated as 
is the manometric liquid density. 
