Patent ID: 8103458

Claim:
An exhaust gas sensing system, comprising: a NH 3 sensing cell configured to generate a first voltage indicative of a combination of a NH 3 concentration and a NO 2 concentration in exhaust gases communicating with the NH 3 sensing cell; a NO 2 sensing cell configured to generate a second voltage indicative of a NO 2 concentration in exhaust gases communicating with the NO 2 sensing cell; a NO x pumping cell electrically coupled to a voltage source that is configured to generate an electrical current through the NO x pumping cell, the magnitude of said electrical current indicative of combination of a NO concentration, a NO 2 concentration, and a NH 3 concentration in exhaust gases communicating with the NO x pumping cell; a current sensor configured to measure the electrical current flowing through the NO x pumping cell and to output a current measurement signal indicative of a magnitude of the electrical current; a computer configured to receive the first voltage, the second voltage, and the current measurement signal, the computer further configured to determine a NO 2 concentration value indicative of the NO 2 concentration in the exhaust gases communicating with the NO 2 sensing cell based on the second voltage; the computer further configured to determine a NH 3 concentration value indicative of the NH 3 concentration in the exhaust gases communicating with the NH 3 sensing cell based on the first voltage and the NO 2 concentration value; the computer further configured to determine a NO concentration value indicative of a NO concentration in the exhaust gases communicating with the NO x pumping cell based on the current measurement signal, the NO 2 concentration value, and the NH 3 concentration value; the computer further configured to determine a NO x concentration value based on the NO concentration value and the NO 2 concentration value; and the computer further configured to store the NO 2 concentration value, the NH 3 concentration value, the NO concentration value, and the NO x concentration value in a memory device.