Method and system for impedance measurement of a zeolite-based ammonia sensor

A method for measuring an impedance of a sensor (S1) that is subject to ion migration includes a number of steps. Initially, a first electrical pulse (VCELL) is applied to an input of the sensor (S1), whose impedance varies according to a first gas concentration in a gas stream. Next, a second electrical pulse (VCELL) is applied to the input of the sensor (S1). The energy of the first and second electrical pulses (VCELL) is approximately the same and the first and second electrical pulses (VCELL) have opposite polarity. A sensor load current (ICELL) is determined during at least one of the first and second electrical pulses (VCELL) to provide a first sensor current (ICELL). Then, the sensor load current (ICELL) during the same one of the first and second electrical pulses (VCELL) is determined to provide a second sensor current (ICELL). Finally, at least one component of the impedance of the sensor (S1) is determined based upon the first and second sensor currents (ICELL).