Exhaust system having cross-sensitive sensor

A power system, comprising:

• an internal combustion engine configured to combust fuel and generate a flow of exhaust;
• an exhaust passage leading from the internal combustion engine to the atmosphere;
• an SCR catalyst disposed within the exhaust passage;
• an injector configured to inject a urea solution into the exhaust passage upstream of the SCR catalyst, the urea solution selected to facilitate within the SCR catalyst a reduction of NOx;
• a sensor disposed within the exhaust passage downstream of the SCR catalyst and configured to generate a signal indicative of a concentration of NOx and NH3 within the exhaust passage;
• and
• a controller in communication with the sensor and the injector, the controller being configured to:
• calculate a value indicative of a rate of change of the signal for a period of time as a cumulative sum of time weighted based on an absolute value of the rate of change of the signal and a flow rate of exhaust through the SCR catalyst;
• determine that the sensor is sensing a concentration of NOx when the value indicative of the rate of change of the signal for the period of time is less than a threshold amount;
• determine that the sensor is sensing a concentration of NH3 when the value of the rate of change of the signal is greater than the threshold amount;
• and
• adjust operation of the injector differently depending on whether the sensor is sensing a concentration of NOx or NH3.

A method of operating an exhaust system, comprising:

• directing a flow of exhaust from a combustion engine through a reduction catalyst;
• injecting reductant into the flow of exhaust to reduce a constituent of the exhaust;
• sensing a concentration of the constituent and the reductant and generating a corresponding signal;
• calculating a value indicative of a rate of change of the signal for a period of time as a cumulative sum of time weighted based on an absolute value of the rate of change of the signal and a flow rate of exhaust through the reduction catalyst;
• making a comparison of the value indicative of the rate of change of the signal for the period of time with a threshold amount;
• making a determination of whether the concentration of the constituent or the reductant is currently being sensed based on the comparison;
• and
• adjusting the injecting based on the determination.