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

We compared the IMGC and NIST standards for small gas flows at the IMGC. 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 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 include 49 nitrogen flow rates from 0.22 mumol s(-1) to 770 mumol s(-1) (1 mumol s(-1) = 1.3448 cm(3) min(-1) of an ideal gas at the 'standard' conditions of 0 degreesC and 101 325 Pa). For all but one of the comparisons, the agreement between IMGC and NIST is better than 0.06%.