Validating Uncertainty Analyses for Gas Flow Standards via Intra- and Inter-laboratory Comparisons

The Fluid Flow Group (FFG) at NESTmaintains flow standards to perform calibrations of gas flowmeters over the 3.7x 10-2L/rein@to 78,000 L/rein flow range. Uncertainty analyses based on the propagation of uncertainties method show that the uncertainties of the provers range from O.16’%o to O.19’?40. The results of inter-laboratory comparisons and intra-laboratory comparisons (i.e., “crossover tests” between two different provers within the NIST laboratory) are examined to verify the uncertainty analysis results. The concepts of shortand Iong-term crossover tests and comparison tolerance are discussed. The comparison test results support the uncertainty specifications for the FFG gas flow standards.