The pressure reading shown by the instrument is the velocity or dynamic pressure, which is the difference of the total pressure, on the high pressure port, and the static pressure, on the low pressure port. The pressure connections of the Pitot Tube are then connected to a differential pressure instrument, such as a manometer or Magnehelic gauge. The space between the inner and outer tubes permits transfer of sensed pressures to the pressure connections on the opposite of the Pitot tube. Radial holes perpendicular to the flow sense the static pressure in the duct.

The flow impacts on one tube pointing directly into the fluid flow that senses the total pressure in the duct or pipe. Pitot Tubes sense the dynamic pressure of the fluid flow at a particular point and were invented by French Engineer Henri Pitot in the early 18 th century.Ī Pitot tube consists of two tubes in one probe that sense both total and static pressure. Pitot tubes are based on Bernoulli’s equation, which states an increase in the speed of a fluid occurs simultaneously with an increase in dynamic pressure and a decrease in static pressure. Dwyer Instruments offers many styles of Pitot tubes, which are a commonly used sensor for monitoring air velocity and flow rate in heating, ventilation, and air conditioning.

Calculating velocity using a pitot tube