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.