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. A typical pitot tube is 25 centimeters long and 1 centimeter in diameter with a hole drilled down the center axis. The tube is pointed into the wind and is typically mounted on the aircraft's wing.

A pressure transducer contrasts the pressure from the pitot tube with the static pressure [which is input through a small hole that is usually on the side of the aircraft and facing perpendicular to the wind] to compute the relative air speed of the aircraft.