Comparison range: 25 l/min to100 l/min
Transfer standard: molbloc-S 5E2 (500 ml/min/kPa) with molbox1 A350K (maximum working pressure of 250 kPa(a))
Test gas: Nitrogen with purity at least 99.999 %
The transfer standard is a molbloc-S, provided by LNE. Its operation is based on a sonic nozzle. It is not a laminar flow element as a traditional molbloc. For flow measurements to be valid, the flow at the throat of the molbloc-S venturi nozzle must be critical, i.e. the gas speed should be equal to the local speed of sound. Critical flow is achieved when a sufficient low back pressure ratio (molbloc-S downstream absolute pressure divided by upstream absolute pressure) is maintained. The sufficiently low back pressure ratia is ensured by vacuum pump.
For a primary standard, it is required to provide a test gas supply with a pressure range from 50 kPa(a). A pressure regulator (Tescom ER 3000) with an automatic controller and a support software ("tuning program") will be attached to the transfer standard package. Every participating laboratory will use a vacuum pump their own and are also responsible for purchasing nitrogen with the required purity.
A workshop for presenting the transfer standard and demonstrating the measurement set-up will be organized by LNE before starting the comparison