After thirty years of discussion, testing and detailed analyses in 1997 there was issued ISO 5801 specifying geometry, way of use including assembly and operation conditions of meters used as testing meters for serial production of ventilation equipment.

Several nozzles (even with different diameters) are assembled on the common plate. It is used for specialised testing equipment, where range of measured flow is adjusted by the number of open (not blinded) nozzles. Its advantage is, that it covers wide range of measurement while using one measuring chamber. On basis of long-term control of special Venturi tubes and multi-nozzles in operation it has been found out that these are very suitable both for specialised testing equipment and for industrial use due quality of measured results, assembly, maintenance and operation.

use: as testing meter for serial production of ventilation equipment.