Patent ID: 6344134
Filing Date: 2002-02-05
Classification: G01N

Abstract:
A method for measuring NOx concentration of a measurement gas containing NOx and oxygen using a two-serial-space NOx concentration sensor comprising a first internal space, a second internal space having a gas inlet, a first pumping cell comprising a solid electrolyte for effecting oxygen pumping with respect to said first space whereby a first pumping current flows through said first pumping cell, a second pumping cell comprising a solid electrolyte for effecting oxygen pumping with respect to said second space whereby a second pumping current flows through said second pumping cell, and a measurement gas space in series communication with said first space and said second space, said method comprising the steps of:introducing said measurement gas into said first space from said measurement gas space; pumping out oxygen from said first space or pumping oxygen into said first space so that the oxygen concentration in the vicinity of the gas inlet to said second space becomes such that a portion of NO in said first space dissociates; dissociating residual NO and oxygen in gas introduced into said second space from said first space; pumping out oxygen ions from said second space which have been generated by the dissociation of said residual NO and oxygen; and determining the concentration of NOx in the measurement gas based on current signals issuing from said first and second pumping cells, wherein the NO dissociation percentage in said first space is not lower than 0.5%.