Venturi meter is a device used to measure the speed and flow rate of fluid through a pipe. It is made up of a U-shaped tube filled partially with mercury. The venturi meter is connected to a pipe at two points as shown in the fig. 11.

           The area of cross sections of pipe at ends where the venturi meter has been connected are A₁ and A₂ respectively. The corresponding velocity of fluid are v₁ and v₂. Let P₁ and P₂ are the pressure of fluid at the two ends 1 and 2.

Bernouilli's equation can be written as,
                       ---------------- ( i )

Fig. 11 :  Venturimeter