Basics of Pitot tube

Pitot Tube

Pitot tube is an apparatus which uses Bernoulli’s theorem, for mathematical analysis to measure flow velocity of fluid.

Bernoulli’s theorem states an increase in the speed of a fluid occurs simultaneously with an increase in dynamic pressure and decrease in static pressure.

Pitot tube is a device used to measure flow velocity of a fluid.

Pitot tubes sense the dynamic pressure of the fluid flow at a particular point.

How Pitot tube works ?

Pitot tube has a rod shaped measuring element that is inserted in to the pipeline perpendicular to the flow direction On the front and rear of this probe are several holes.Two separate tubes connects these holes to a differential pressure sensors.With its two pressure chambers separated by a diaphragm.The tiniest pressure differences in the flowing fluid can be precisely measured. The individual pressure taps are distributed along the entire pipe cross section to ensure a representative measurement.

If there is a strong interference in the flow profiles its advisable to fit a second pitot tube rotated by 90 degrees.

If the fluid is not flowing,the pressure before and after the probe is essentially the same.As soon as the fluid starts to flow an additional impact pressure against the front of the probe is generated also known as the dynamic pressure.On the rear of the probe in contrast only the static pressure which is not related to the flow is still measured.As a result different values are detected in the pressure chambers of the sensor higher pressure against the flow and constant pressure on the rear of the pitot tube.This pressure difference is a direct measure for the flow velocity and thus the mass and volume flow in the pipe.

The higher the flow velocity and therefor the dynamic pressure the greater the differential pressure measured.

Pitot tube are able register the flow in both flow directions.

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