| 摘要 |
PURPOSE: To precisely detect nitrogen oxide concentration with comparatively simple constitution, by supplying oxygen to measurement gas which contains reducing gas, from an electrochemical cell, and detecting nitrogen oxide after passing oxidation catalyst by using a semiconductor sensor. CONSTITUTION: A negative voltage is applied to an electrode 12, and a positive voltage is applied to an electrode 13, thereby applying a voltage V to an electrochemical cell 10. Generated oxygen is sent into a volume chamber 15 by using circulating air 4 and mixed with measurement gas 2 which flows in via a passage 16. When the mixed gas is made to pass oxidation catalyst, CO and hydrocarbon are oxidized, turned into CO2 and H2 O, and NO2 is left as it is. NO is turned into NO2 , or left as it is. As a result, it is possible that the gas which passes the catalyst 17 and permeates a quantitative chamber 18 contains NO2 and NO as the active component. These NO2 and NO are detected by using a nonselective nitrogen oxide sensor 19. Accordingly, the concentration of nitrogen oxide can be directly measured from the signal output of the sensor 19, when reducing gas exists in the measurement gas 2 before passing oxide catalyst 17. |
