Digession on O2 Sensors

[ptimmerm at mashtun.JPL.NASA.GOV]

>Everybody should keep in mind that the (so called) lambda sensor is not
>measuring O2 or A/F at all.  What it is is a galvanic cell which (at
>temperature) will generate a voltage from EACH and EVERY component of the
>exhaust gases.  The voltage contribution of each of these is proportional to
>their partial pressures, as well as some constants relating to their size
>(permittivity of the sensor), and their electronegative potential. 

All though not an electrochemist (no pHd) I do play one on TV.
Most of what you say above is correct, but you may be headed the
wrong way with it.  The ceramic used is a solid oxide that conducts
oxygen at high temperatures.  I doubt anything else is is transported
across the oxide.  This would effectively remove all other gases
from the couple.  I could be wrong, but I don't think so.

paul timmerman
electrochemcial system group
jet propulstion labs
pasadena ca