Patent ID: 7776194
Filing Date: 2010-08-17
Classification: G01N

Abstract:
1. A gas concentration measuring apparatus comprising: a gas concentration sensor which includes a solid electrolyte body to be exposed to an exhaust gas within an exhaust system of an internal combustion engine; a sensor control circuit which works to control an operation of said gas concentration sensor and operate in a gas measuring mode and a reference output mode selectively, in the gas measuring mode, said sensor control circuit applying a voltage to said gas concentration sensor and sampling a resulting flow of electric current through said gas concentration sensor to produce a gas concentration output as a function of a concentration of a given component of the exhaust gas, in the reference output mode, said sensor control circuit being placed in a condition which is equivalent to when the exhaust gas is in a preselected atmosphere and in which a reference output is produced insensitive to the exhaust gas; a switching circuit working to switch a mode of operation of said sensor control circuit from the gas measuring mode to the reference output mode; and a correcting circuit working to sample a value of the reference output as produced by said sensor control circuit being placed in the reference output mode and find an error of the gas concentration output of said sensor control circuit as a function of a difference between the sampled value of the reference output and a corresponding normal reference output as expected to be attained by said sensor control circuit correctly when the exhaust gas is in the preselected atmosphere to determine a correction factor, said correcting circuit correcting the gas concentration output of said sensor control circuit using the correction factor so as to compensate for the error; wherein the reference output mode is established by placing said sensor control circuit in a virtual stoichiometric air-fuel ratio measuring mode equivalent to an operation mode in which said sensor control circuit produces the gas concentration output when the exhaust gas results from burning of a stoichiometric mixture in the engine; and said switching circuit switches the mode of operation of said sensor control circuit from the gas measuring mode to the reference output mode at a stated time interval.