Author： Knopf D. Barbe J. Richter W. Marschal A.
Publisher： IOP Publishing
ISSN： 0026-1394
Source： Metrologia, Vol.38, Iss.3, 2001-06, pp. : 197-202
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Abstract
Gas mass flows can be measured most accurately using continuously measuring dynamic-gravimetric systems. Two systems of this type, the mass flow calibration system at the Bureau National de Métrologie-Laboratoire National d'Essais (BNM-LNE, France) and the mass flow calibration system at the Physikalisch-Technische Bundesanstalt (PTB, Germany), were compared twice using a commercial gas flow measuring instrument as a transfer standard. Mass flow rates of nitrogen between 0.5 mg/s and 20 mg/s (approximately 25 ml/min to 1000 ml/min) and mass flow rates of carbon monoxide between 0.5 mg/s and 10 mg/s (approximately 25 ml/min to 500 ml/min) were used to check the agreement of the two calibration systems. The results of the comparison show that the two systems do not deviate by more than 0.23 % for flow rates higher than 2 mg/s. For lower flows, down to 0.5 mg/s, the differences increased to as much as 0.37 %. The reason for this is not yet understood.
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