O2 Volts

[rr]

soren wrote:
> 
>  Varying the amounts of HC, CO,
> >CO2, and NOx don't affect the sensor. Only O2 quantity in relation to
> >the sensor's reference changes voltage.  TPS senses TP whether output
> >voltage increases or decreases with increased throttle angle.  Why do
> >you think an "inverted" output from the O2 sensor makes it a Not O2
> >sensor?
> 
>     A TPS has a supply voltage that can be modulated in either increasing or
> decreasing fashion with increasing throttle angle, but the O2 sensor has to
> make its own voltage.  My simple logic led me to the conclusion that the
> compound that is being actually being sensed must be the one that provides
> this positive voltage.
> Then I remembered that the O2 sensor is actually a differential sensor, like
> you said: it provides voltage based on the differential between the outside
> reference air and the gases in the exhaust.  So my new hypothesis is that
> the sensor is sensing O2, but it actually produces voltage from the
> reference oxygen; when it is compared to an oxygen-poor environment in an
> exhaust stream, there is a voltage differential across the ion-sensing
> electrodes, and the voltage produced at the reference side goes up the
> signal wire.  When the O2 is even on both sides, no voltage is produced.
>     Of course, this would only apply to the zirconium type O2 sensors, the
> titanium dioxide ones do actually use a reference voltage and act as a
> variable resistor.
>     So now what I want to see is someone test a sensor using sealed chambers
> for both reference and exhaust sides, using O2, HCs, an inert gas such as
> argon, and another gas containing negative ions (maybe one of the halogens)
> as a control. :-p
> 
> Soren

Check out the SAE articles that were pointed too, this is the kind of
thing that the epa was doing:

http://vehicle.me.berkeley.edu/~markw/efi/SAE920289/
http://vehicle.me.berkeley.edu/~markw/efi/SAE930352/ 

They are interesting reading.

BobR.

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