| 摘要 |
PURPOSE: To realize continuous accurate measurement with high response for a long time regardless of the oxygen concentration by introducing the atmosphere in an inner cavity, controlled not to have any effect on the gas component to be measured, to a next inner cavity under a constant diffusion resistance and then measuring the gas. CONSTITUTION: A gas to be measured is introduced through a diffusion rate- determining path 12 to an inner cavity 6 where the partial pressure of oxygen is controlled to a level low enough not to cause reduction of NOx by an oxygen concentration control means, i.e., an electrochemical pump cell 56. Atmosphere in the inner cavity 6 thus controlled is introduced into an inner cavity 8 communicating the inner cavity 6 through a diffusion rate-determining path 14 and NOx is reduced in the inner cavity 8. Oxygen produced through reduction is pumped up from the inner cavity 8 under reduction rate-determining conditions using an electrochemical pump cell 58 and the quantity of NOx in the gas to be measured is determined based on the value of current flowing through the electrochemical pump cell 58. |
