Patent ID: 6055840
Filing Date: 2000-05-02
Classification: G01N

Abstract:
A method for calibrating a gas measurement device comprising a gas sensing element having an electrical signal output dependent upon concentration of a gas being measured, means for measuring the electrical signal output and means for limiting diffusion of the gas being measured to the gas measurement device and defining a path for gas being measured to enter the gas measurement device, comprising the steps of:exposing the gas sensing element through a first gas path to a gas to be measured at a test concentration at a first rate of diffusion and first diffusivity, and measuring the output signal for a time sufficient to establish a first steady state signal;exposing the gas sensing element through a second gas path to the gas to be measured at a second, reduced rate of diffusion and second diffusivity, and measuring the output signal for a time sufficient to establish a second steady state signal;determining either the first or second diffusivity based on a known coefficient of diffusion for the gas and physical dimensions of the first or the second gas path;calculating the test concentration of the gas based on the determined diffusivity and the first and second steady state output signals; andcorrecting subsequent measurements based on the calculated test concentration of the gas.