| 摘要 |
PROBLEM TO BE SOLVED: To obtain a sensor which can obtain a large signal change and by which a measurement can be 'performed continuously, with good responsivity and precisely for many hours. SOLUTION: An atmosphere in a first internal space 6 whose oxygen partial pressure is controlled to a low value by an electrochemical pump cell is guided to a second internal space 8 which communicates with the first internal space 6, NOx are reduced or decomposed by an NOx reduction catalyst, an oxygen partial pressure inside the second internal pressure is increased by generated oxygen, and the pressure grade of the oxygen partial pressure between the second internal space 8 and the first internal space 6 is generated. An oxygen flow keeps the pressure grade by a prescribed diffusion resistance provided by a second diffusion velocity control means, and the oxygen flow is balanced by a value which is higher than the oxygen partial pressure in the first internal space so as to correspond to an NOx concentration in a gas to be measured. Then, an electromotive force which corresponds to the oxygen partial pressure in an atmosphere inside the second internal space is detected by an output from an electrochemical sensor cell. |
