Patent ID: 7578914

Claim:
A gas concentration measuring apparatus designed to sample an output of a gas concentration sensor which includes a sensor element made of a solid electrolyte body working to produce an electric current as a function of concentration of a given gas component, comprising: a first signal output circuit designed to output a first sensor signal as a function of an electric current produced by the sensor element for use in determining a concentration of the given gas component in a first gas concentration range; a second signal output circuit designed to output a second sensor signal as a function of the electric current for use in determining a concentration of the given gas component in a second gas concentration range different from the first gas concentration range; and a gas concentration determining circuit configured to sample the first and second sensor signals to determine the concentrations of the given gas component in the first and second gas concentration ranges, said gas concentration determining circuit analyzing a value of the first sensor signal to determine a first output characteristic error that is a difference between an actual output characteristic and a stated reference output characteristic of said first signal output circuit, sampling values of the first sensor signal and the second sensor signals when the gas component lies within the second gas concentration range, calculating an actual concentration of the gas component using a concentration of the gas component indicated by the sampled value of the first sensor signal and the first output characteristic error, determining a difference between the value of he second sensor signal sampled upon calculation of the actual concentration of the gas component and a corresponding value of a stated reference output characteristic of the second signal output circuit as a second output characteristic error of the second signal output circuit.