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Volume flow rate primary element Wilson flow grid

Volume flow rate primary element Wilson flow grid

Maximum accuracy for measuring the volume flow rate / flow in air ducts


Volume flow rate primary element with maximum accuracy for flow and volume flow measurement in ventilation ducts

Special features

  • Suitable for round or square ducts
  • Installation that fits accurately in the duct
  • Numerous measuring points with pitot tubes arranged parallel as grids or star-shaped around a hub
  • Maximum accuracy
  • Stainless steel (round flow grids are optionally available in aluminium)

Round flow grids consist of tubes arranged in a star shape (around a hub). These tubes have boreholes (measuring points), half of which record the total pressure while the other half record the sub-static pressure. In the central hub, the pressures are collected separately and routed to the pressure connection nozzles via small capillary tubes. The pressure differential thus obtained is proportional to the flow rate or volume flow rate.

Rectangular flow grids consist of tubes arranged in parallel. They form a kind of “fence” at right angles to the flow. These tubes have a row of boreholes (measuring points) of the same size. On one hand, they point directly against the flow and collect the total pressure, and on the other they point downstream and record the “sub-static” pressure. These pressures are always averaged and outwards via collecting pipes.

Shape and size of grids
Round flow grid: Diameter of 100 .. 1100 mm
Square flow grid: Dimensions of 100×150 mm up to 450×450 mm
Other dimensions on request

Maximum accuracy

Measuring points
Numerous measuring points

Ventilation duct with several fixtures

Operation temperature
Round flow grids:
Stainless steel: permanently up to 450°C
Aluminium: up to max. 80°C

Square flow grids:
Standard versions: no more than 80°C
Fully welded special versions: up to 450°C

Stainless steel 1.4541 (standard)
Aluminium (optional for round flow grids 150 .. 560 mm)