Abstract: A sensor includes an oxygen pump cell; an oxygen pump chamber; an emf cell; a reference chamber providing a fluid connection to the reference gas; gas channels in fluid communication with the pump and emf electrodes, the reference gas comprising reformate produced by a fuel reformer fueled by an air-fuel gas mixture having an air-fuel ratio; a reformer electronic control module; a sensor electronic control module; a heater; a temperature sensor disposed in communication with the heater and the sensor control module for maintaining the sensor at a desired operating temperature; a closed loop controlled operation amplifier in electrical communication with the sensor, whereby the oxygen pump cell provides sufficient oxygen ions to oxidize an incoming diffusion-limiting fuel flux to the emf cell and maintain a constant emf at the emf cell, and wherein a current value represents an equivalent to the air-fuel ratio of the air-fuel gas mixture.

Abstract: A technique for reducing a parasitic DC bias voltage on a sensor monitors the parasitic DC bias voltage on a first element of the sensor. A controlled bias voltage that is applied between the first element of the sensor and a second element of the sensor is then modified to substantially maintain the parasitic DC bias voltage at a desired potential.

Abstract: A technique for measuring an impedance of a sensor that is subject to ion migration includes a number of steps. Initially, a first electrical pulse is applied to an input of the sensor, whose impedance varies according to a first gas concentration in a gas stream. Next, a second electrical pulse is applied to the input of the sensor. The energy of the first and second electrical pulses is approximately the same and the first and second electrical pulses have opposite polarity. Next, a sensor load current is determined during at least one of the first and second electrical pulses to provide a first sensor current. Then, the sensor load current during the same one of the first and second electrical pulses is determined to provide a second sensor current. Finally, at least one component of the impedance of the sensor is determined based upon the first and second sensor currents.