A new high precision, broad range gas micro-flow calibration apparatus. (June 2019) - Guo, Meiru
Abstract: In this paper, a new calibration apparatus has been developed for gas micro-flow calibration. The apparatus employs both the constant volume method and the constant conductance method. The calibration range from 10 −1 to 10 −13 Pa·m 3 /s, and the combined standard uncertainty is 1.2%∼1.8%. When calibrating extremely low gas flow rate, the non-evaporable getter pump is used to reduce the effect of chamber wall outgassing on the measurement results, so that the lower limits of the constant volume method and constant conductance method are extended to 10 −10 Pa·m 3 /s and 10 −13 Pa·m 3 /s, respectively. Then a method for measurement of orifice conductance is proposed, the on-line precise measurement of the orifice conductance is realized; the consistency of flow measurement results by constant volume and constant conductance methods is better than 1.3%, then compared with the same standard leak was calibrated in both constant conductance method of the calibration apparatus and the constant pressure gas micro-flow calibration apparatus of the laboratory, and the deviation of those results was less than 1%. Highlights: The gas micro-flowmeter is combined with the constant volume and the constant conductance methods. The constant volume chamber adopts NEG pump static pumping mode, the lower limit extended to 2×10 −13 Pa·m 3 /s. The method for measurement of orifice conductance is proposed, and the curve of orifice conductance was obtained. The new apparatus is consistent with the results of the constant pressure calibration apparatus.