NIST-IMGC Comparison of Gas Flows Below 1 Liter per Minute
Robert F. Berg, G Cignolo
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 to 660 micromol/s = 1.3443 cm^3/min of an ideal gas at the standard conditions of 0 C and 101325 Pa.) For all but one of the comparisons, the agreement between IMGC and NIST is better than 0.06%.