Patent ID: 6119710
Filing Date: 2000-09-19
Classification: G01F,G05D,Y10T

Abstract:
A method of measuring mass flow in a gas delivery system, comprising operations of:charging a calibration volume with a process gas;starting a flow of the process gas from the calibration volume into a flow path; during gas flow,repeatedly utilizing one or more sensors downstream of the calibration volume to take pressure measurements and performing a computational process using data including the pressure measurements to compute a measured mass flow rate through a flow restrictor in the path;repeatedly performing operations comprising: measuring pressure and determining the temperature of the gas in the calibration volume, using a time rate of change of the measured pressure and the determined temperature to compute an actual mass flow rate of gas flowing from the calibration volume, and determining whether there is any discrepancy between the actual mass flow rate and the measured mass flow rate; andwhenever a discrepancy is found, correcting the computational process such that the measured mass flow rate matches the actual mass flow rate thereby eliminating the discrepancy.