by John Wright, Gina Kline, Kevin John, Brian Novitsky, Jason Bellavance, Kevin Shufelt, Bradley Nease, Miles Owen, Joe Allen, Casey Rombouts, William Gause, John Cuccio
A comparison of seven gas flow calibration laboratories piloted by NIST used four laminar flow meters as the transfer standards for nine nitrogen gas flows ranging from 1 sccm to 10 slm. The comparison reference value was calculated from the uncertainty weighted average of the three participants with independent flow traceability chains. The 63 comparison results were evaluated by the traditional criterion and also by a probabilistic criterion that allows the possibility of inconclusive results. The traditional criterion determined that 2 of the 63 results were outside of uncertainty expectations. The probability-based criterion found the same 2 results were outside of uncertainty expectations and 3 results were inconclusive. Based on these results and other evidence, all participants were found proficient over the range of flows they tested. A comparison of the present results to those from a similar comparison between four of the same participants conducted in 2003 shows that the labs have improved their flow measurement capabilities by a factor of three.
