The measuring grid SGI is an arrangement of several cylinder probes which are distributed over a cross section in pipes, channels etc. It is a speed measurement similar to the Prandtl Pitot tube. The special design of the SGI grid has an array of probes which are present in a wide range independent of the Reynolds number coefficient C=2. The probes are adapted to the tubes or duct dimensions and can produce circular or rectangular channel cross-sections. For a larger diameter a thrust bearing is used to measure the speed.