Patent ID: 6645367
Filing Date: 2003-11-11
Classification: G01N

Abstract:
A method of determining a NOx concentration in a gas, which comprises:providing a measuring sensor with a first measuring cell and a second measuring cell connected to the first measuring cell; introducing a portion of a gas into the first measuring cell and adjusting a first oxygen concentration with a first oxygen-ion pumping current; inroducing gas at the first oxygen concentration from the first measuring cell into the second measuring cell and adjusting a second oxygen concentration in the second measuring cell with a second oxygen-ion pumping current; decomposing NOx present in the gas at the second oxygen concentration within the second measuring cell; pumping oxygen present in the gas after decomposition of NOx form the second measuring cell with a third oxygen-ion pumping current; measuring a NOx concentration with a measuring electrode in the second measuring cell by measuring the third oxygen-ion pumping current to obtain a measured value of the NOx concentration; and correcting the measured value of the NOx concentration by the following equation: NOx=fÂ·NOxâ€²+a â€ƒwherein NOxâ€² is the measured value of the NOx concentration and f and a are correction values taken from a characteristic map in dependence on at least the second oxygen-ion pumping current.