NIST-IMGC comparison of gas flows below one litre per minute

The standards of IMGC and NIST for small gas flows were compared at the IMGC laboratory. The IMGC standard is a recently developed primary flow meter that extracts a large piston out of a temperature-controlled chamber. Controlling the piston's speed holds the pressure in the chamber constant. The NIST standard is a recently developed transfer standard that was calibrated against two primary standards at NIST. The first NIST primary standard extracts a large piston out of an oil-filled chamber in which a metal bellows is suspended. Controlling the piston's speed holds the pressure in the bellows constant. The second NIST primary is a static gravimetry method. The results of the comparison include 49 nitrogen flow rates from 0.22 micromol/s to 770 micromol/s. For all but one of the comparisons, the agreement between IMGC and NIST is better than 0.06%