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About Pitot Tubes

The Pitot tube is named for Henri Pitot, who invented it in 1732.  Henry Philibert Gaspard Darcy, another Frenchman, published a paper in 1858 that made improvements on Pitotís invention.  The first patent for the use of a Pitot tube to measure velocity in pipes was given to Henry Fladd of St. Louis, Missouri, in 1889.  

Pitot tubes are of two types:

        Single port

        Multiport averaging Pitot tubes



A single port Pitot tube includes an L-shaped tube measuring impact pressure.  This tube is inserted into the flowstream, with the opening facing directly into the flow.  Another tube measuring static pressure has an opening parallel to the direction of flow.  Flowrate is proportional to the difference between impact pressure and static pressure.

A multiport averaging Pitot tube has multiple ports to measure impact pressure and static pressure at different points.  The DP transmitter computes flowrate by taking the average of the differences in pressure readings at different points.

Some companies such as Emerson Rosemount and Veris have introduced proprietary versions of the averaging Pitot tube.  Emerson Rosemountís proprietary version is called the Annubar, and it was formerly sold by Dieterich Standard, now part of Emerson Process Management.  Verisí averaging Pitot tube is called the Verabar.

Verabar Multiport Averaging Pitot Tube. Photo courtesy of Veris.

For further information on differential pressure, including studies and articles, see www.FlowDP.com.

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Flow Research, Inc. | 27 Water Street | Wakefield, MA 01880 | (781) 245-3200 | (781) 224-7552 (fax) | (800) 245-1799 (from the USA) | info@flowresearch.com

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