Patent ID: 7217355

Claim:
An apparatus for determining NO x concentration of an exhaust gas, the apparatus comprising; an input assembly capable of receiving the exhaust gas and producing a conditioned output gas, the input assembly including at least three of the following four stages: a first stage including a first catalyst structure for converting NH 3 in the exhaust gas to N 2 and H 2 O, the first catalyst structure comprising a catalyst material from the group consisting of Cu, Ag, NiAl 2 O 4 , MnO 2 , V 2 O 5 , and any mixture thereof; a second stage including a second catalyst structure having an absorbent material for absorbing SO 2 or H 2 S from the exhaust gas; a third stage including a third catalyst structure for oxidizing unburned hydrocarbons and gases to higher oxidation states; and, a fourth stage including a fourth catalyst structure for establishing a steady state equilibrium concentration ratio between NO and NO 2 ; and, a NO x sensor operably connected to the input assembly and receiving the conditioned output gas of the input assembly wherein the concentration of the total NO x present can be determined.