Temperature characterization in the collection tank of the NIST 26 m3PVTtgas flow standard

Abstract

Gas temperature gradients created during the filling stage of a pressure–volume–temperature–time ( PVTt ) calibration cycle, and those imposed by inhomogeneous room conditions, lead to uncertainties in the average gas temperature in the collection tank. Because these temperature uncertainties dominate the overall flow uncertainty, NIST upgraded the temperature-averaging scheme used in its 26 m 3 PVTt system. Instead of arithmetically averaging 10 thermistors to obtain the mean gas temperature, we now calculate this value via a volume-weighted trapezoidal integration procedure using 35 thermistors. Applying the new temperature-averaging scheme, the mean gas temperature can be determined with a standard uncertainty of 89 mK after only 2700 s of fan mixing. As a result, the flow uncertainty in the NIST 26 m 3 PVTt system has decreased from 0.22% to 0.13% (with a coverage factor of 2). This paper highlights the temperature improvements and presents a detailed analysis for estimating the lower temperature uncertainty.

Cite this work

No public copy is stored for this record, so only the metadata is cited.

Stored only when both papers are in the corpus — 12 citations exist upstream.

Papers that cite the same references — the relational fallback while embeddings are still backfilling.