| 摘要 |
PROBLEM TO BE SOLVED: To provide a nitrogen oxides measuring method of extremely high accuracy hardly influenced by the concentration of oxygen and water vapor in measured gas and hardly fluctuated by temperature change. SOLUTION: Using a main pumping means 60 with an electrochemical pump cell 6, and a sensor provided with an electric signal converting means 70, measured gas is led from external space into a first internal void 2 communicated with the external space, under first diffusion resistance, and oxygen partial pressure in the atmosphere of the first internal void 2 is controlled to the specified low value so that NO is not substantially decomposed. The controlled atmosphere in the first internal void 2 is led to a second internal void 9, under second diffusion resistance, and converted into an electric signal, corresponding to the quantity of oxygen generated by decomposing or reducing NOx in the atmosphere, by an electric signal converting means 70 so as to measure nitrogen oxides in the measured gas. In such a method, an electrochemical cell 12 is provided to detect oxygen concentration in the second internal void 9, and control voltage applied to the main pumping means 60 is corrected on the basis of the output of the electrochemical cell 12. |
