Stepped linear piston displacement fundamental leak calibration system

Abstract

A fundamental leak calibration apparatus has been developed that measures gas leak rates. The stepped linear piston displacement (SLIPD) system decreases the calibration time for leaks in the 10−11–10−6 mol/s (2×10−7–2×10−2 atm cm3/s at 0 °C) range without increasing the uncertainty when compared to other related techniques. Calibration times have been reduced by up to a factor of 10 (depending on the leak rate) over the current P ΔV system used by the Sandia Primary Standards Laboratory for more than four years. The SLIPD system is computer controlled and requires minimal operator input. Furthermore, the total systematic uncertainty of <±1.1% (from 10−10 to 10−6 mol/s) is roughly the same as that for a P ΔV system and intercomparisons between the two systems for the same leaks agree to better than ±1.0%.