Pitot tube

A Pitot tube, invented by Henri Pitot and modified to its modern form by Henry Darcy, is a measuring instrument used to measure fluid flow. The basic instrument consists of two coaxial tubes: the interior tube is open to the flow, whilst the exterior tube is open at ninety degrees to the flow. A manometer can be used to meaure the difference between these two pressures and using Bernoulli's equation the flow rate of the fluid can be calculated.

Pitot tubes are commonly found on aircraft and are used to measure the speed of the aircraft through the air.