Patent ID: 6623617
Filing Date: 2003-09-23
Classification: G01N,Y02A

Abstract:
A method for measuring the concentration of a component of a gas under measurement by use of a sensor comprising: a first chamber equipped with a first oxygen ion pump cell, which comprises a solid electrolyte layer and a pair of electrodes; a second chamber equipped with a second oxygen ion pump cell, which comprises a solid electrolyte layer and a pair of electrodes; a first diffusion passage for establishing communication between the first chamber and the gas under measurement; and a second diffusion passage for establishing communication between the first chamber and the second chamber;said method comprising the steps of: applying a pump voltage to the first oxygen ion pump cell so as to reduce the concentration of oxygen in the gas under measurement to be introduced into the second chamber; introducing into the second chamber through the second diffusion passage the gas under measurement which has undergone reduction of oxygen concentration within the first chamber, and applying a pump voltage to the second oxygen ion pump cell; measuring a first pump current flowing through the first oxygen ion pump cell; measuring a second pump current flowing through the second oxygen ion pump cell; and obtaining from the second pump current the concentration of said component in the gas under measurement introduced into the first chamber by use of a non-linear expression which expresses an approximated relationship between the second pump current and the concentration of said component in the gas under measurement, wherein the concentration of the component of the gas under measurement is 100 ppm or less.