Abstract: An on-board catalytic monitoring system uses an intrusive technique to cause the vehicle's engine to cycle between first and second operating conditions. The first and second operating conditions are chosen such that different concentrations of emissions with different chemistries are present at the first and second operating conditions. A calorimetric sensor with a selective catalyst senses exothermic oxidation reactions produced by the emissions in the exhaust gas passing over the sensor. By matching the catalyst activity with the emission concentrations occurring at the operating conditions, the difference between the heat release sensor signals detected between the first and second operating conditions is indicative of the actual concentration of specific emissions in the exhaust gas stream. The difference or delta signal, obtained without reference to a zero point, provides an excellent correlation to the efficiency of the vehicle's catalytic converter for converting the sensed emission, i.e.

Abstract: A calorimetric sensor system requires a vehicle's internal combustion engine to cyclically operate between first and second conditions to repeatedly produce a varying exhaust gas composition which is consistent from cycle to cycle. The rate of change of the calorimetric sensor's signal as the engine cycles from one to the other condition is mathematically factored, after signal filtering at frequencies of the induced perturbation, to provide signals indicative of the emissions concentration in the exhaust gases, the air/fuel ratio of the engine and whether the engine is operating lean or rich. The signals can be used as fuel control engine signals as well as OBD signals. Additionally, the system can control industrial processes through small process perturbations affecting the compositions of process gases.