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US 6,645,367 B1Granted
Method for determining a nitrogen oxide concentration
AssigneeSiemens Aktiengesellschaft
InventorsHong Zhang, Jürgen Rössler
Life of this patent
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Abstract
The NOx concentration in a gas is determined with a thick-film measuring sensor which has two measuring cells. The raw measured value of the measuring sensor is corrected by a multiplicative correction value and an additive correction value, which are both taken from a characteristic map. The characteristic map depends on the oxygen-ion pumping current in the second measuring cell, the measured gas temperature, and the measuring sensor temperature.
Claims7
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=f·NOx′+a
- wherein NOx′ 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.
7 more elements
Dependencies are inferred from the claim text.