resulting from alternating input waveforms for example by using an asymmetric sawtooth input waveform and alternating the direction of the asymmetry the dominant gas species effect can be measured separately with each alternating waveform in some embodiments the use of asymmetric alternating input waveforms may yield more accurate measurements for certain gas species measurements for temperature and other characteristics of the exhaust stream may also be taken by alternating input waveforms specific to measurement of that species or characteristic fig3 f depicts an embodiment of response signals corresponding to varied gas species concentrations while fig3 a e depict results gathered from steady state experiments fig3 f demonstrates results gathered with variations in gas species concentrations fig3 f illustrates the effect of no and o 2 on the sensor output in particular no appears to constantly move the signal downward while o 2 has tendencies to reverse the polarity of the signal in certain regions fig4 depicts one embodiment of a flow chart diagram of a method 70 for measuring gas species using voltage current differential in the time domain the method includes identifying 72 an affected region of an affected waveform signal corresponding to at least one characteristic of the gas stream the method 70 also includes calculating 74 a difference between the affected region of the affected waveform signal and a corresponding region of an original waveform signal wherein the affected region and the corresponding region of the waveform signals have a sensitivity specific to the at least one characteristic of the gas stream the method 70 also includes generating 76 a value for the at least one characteristic of the gas stream based on the calculated difference fig5 depicts one embodiment of a flow chart diagram of a method 80 for.