TSI / Airflow | Pitot tubes | 90 degree

Contact Instrument Solutions

Developed between 1952 and 1954 by the National Physical Laboratory the modified ellipsoidal nose pitot static tube is recommended in BS ISO 3966 : 2008 (previously BS 1042 Part 2. 1 : 1983) for measuring the flow of air in ducts by the traverse method.

When inserted into a duct with the tip facing directly into the flow it will enable air velocity at that point to be determined by connecting the static pressure and total pressure tapping's to opposite sides of a sensitive manometer. The manometer will show the difference between the two pressures. This is the velocity pressure from which the air velocity can be calculated.


The pitot static tube consists basically of two concentric tubes, with the end turned through a right angle so that the tip can be faced into the airstream after insertion through the duct wall. The modified ellipsoidal nose form has a single forward facing hole for sensing Total Pressure and a ring of side holes for sensing the Static Pressure. Both these inlets are individually connected to tapping outlets at the tail of the unit. A direction pointer is provided so that the pitot tube can be accurately aligned within the duct.

Constructed entirely in stainless steel with welded joints, the tube can be safety exposed to temperatures up to 680 °C and for short periods up to 800 °C. Exceptions to this are the 2.3 mm and 4 mm diameter tubes, which have silver brazed joints. These are only suitable for temperatures up to 550 °C. Sliding spring clip markers are fitted to the 4 mm, 8 mm and 9.5 mm diameter pitot tube stems (not on glanded pitots) to indicate depth of insertion and can be used at temperatures up to 276 °C. The combined features of the spring clip markers and pointer greatly simplifies correct positioning of the tube when making a traverse.

For permanent installations some of the smaller sizes can be supplied with a gland fitted on the stem. After attaching the gland to the duct wall, the pitot can be slid through the gland to the required position and locked in place by tightening a nut. Please call our sales team on 01344 459314 for pricing.

  • Modified ellipsoidal nose pitot tube as recommended in BS ISO 3966 : 2008
  • Direction pointer on tail piece to ensure correct alignment
  • Can be used in permanent position when fitted with gland
  • Ridged connectors to suit PVC connecting tubing
  • Supplied as standard with adjustable position ring markers


  • Only a few small access holes required - saves time and money
  • Compatible with all manometers
  • No worries about pressure drop - Air does not pass through the instrument


  • Can be used in hostile environments. e.g. flue stacks
  • Combustion efficiency tests
  • Research testing
  • HVAC commissioning
  • Heat exchanger balancing
  • Process control lines.

Supplied as standard with adjustable position ring markers - various lengths available.

Demonstration videos

TSI training video - How to set an instrument up do a duct traverse
TSI training video - How to perform a duct traverse

Support documents

  • Download
  • Category
  • File type
  • Download
TSI Air velocity & volume application note.pdf TSI Air velocity & volume application note
Technical document
File type
Adobe Acrobat
Download (285 KB)