Method and apparatus for measuring and providing corrected gas flow

Claim 1

A process of measuring a variable in a range between first and second values thereof employing a voltage dependent element whose impedance varies as a function of the measured variable for providing a manifestation indicative of the measured variable, said process comprising the steps of: (a) applying a voltage to said variable measuring element and a reference element, whose impedance is relatively stable; (b) exposing said variable measuring element to said first value of said variable, and deriving from said variable measuring element and said reference element corresponding first and second signals; (c) exposing said variable measuring element to said second value of said variable, and deriving from said variable measuring element and said reference element corresponding third and fourth signals; (d) obtaining a first calibration ratio of said first to said second signals and a second calibration ratio of said third to said fourth signals; (e) exposing said variable measuring element to an unknown variable and deriving from said variable measuring element and said reference element corresponding fifth and sixth signals a fluctuating voltage being applied commonly to said variable measuring element and said reference element; (f) deriving a present ratio of said fifth to sixth signals; (g) interpolating said present ratio with respect to said first and second calibration ratios to provide said manifestation of the measured variable substantially free of any fluctuation of the level of said voltage.