Calibration procedures for standard gas leaks

Calibration procedures for equipment used in measuring flow rates of standardized gas leaks using a mass spectrometer are discussed. The calibration involves measurements of temperature, time, pressure and volume. The mass spectrometer is calibrated with a calibrated micromanometer and pure gas. The micromanometer is calibrated using a volume expansion method and a quartz fiber manometer in the torr range. Apparent volumes in the mass spectrometer inlet systems are calibrated using a quartz fiber manometer. Error analysis is made by using the partial derivative method and the square root of the sum of squares method. The following error contributions were determined: volume +-0.6% temperature +-3.6% (helium only), time +-0.4%, pressure +-4.6%. For helium diffusion leaks an additional error 0.6% was determined as the contribution for alpha the temperature correction factor.