초록

The low voltage preferably applied in the above (3) is about 350-450 mV.

대표청구항 ▼

[ What is claimed is:] [1.]1. A method for determining NOx concentration in a measurement gas comprising NOx, O.sub.2, CO.sub.2 and H.sub.2 O, under a varying condition of the NOx concentration in the measurement gas in the course that the measurement gas is allowed to travel through a flow channel

[ What is claimed is:] [1.]1. A method for determining NOx concentration in a measurement gas comprising NOx, O.sub.2, CO.sub.2 and H.sub.2 O, under a varying condition of the NOx concentration in the measurement gas in the course that the measurement gas is allowed to travel through a flow channel facing a ceramic body having an electrically controllable conducting rate of oxygen ion,wherein the method comprises:(1) introducing the measurement gas into the flow channel;(2) forming an NO-concentrated residual gas in said flow channel under a condition that allows substantial decomposition of NOx, said NO-concentrated residual gas having a NOx concentration different from the measurement gas and extracting said O.sub.2 from the measurement gas introduced into the flow channel;(3) dissociating NO of said NO-concentrated residual gas into nitrogen and oxygen by applying across electrodes formed on the ceramic body a voltage to an extent that does not substantially dissociate said H.sub.2 O or said CO.sub.2 in the NO-concentrated residual gas;(4) measuring an electric current flowing through the ceramic body between the electrodes, said electric current being generated by an electrochemical action of the oxygen dissociated from the NO in step (3); and(5) determining the NOx concentration of the measurement gas based on the electric current measured in step (4).