O2 voltz

[Shannen Durphey]

David A. Cooley wrote:
> 
> At 04:02 PM 5/15/99 -0400, you wrote:
> >For the lack of anything else to do, I hooked the heated O2 up, and was
> >looking at the voltage drop across a sensor resistor, I been thinking of
> >using.
> >  As the heater warmed up, the voltage drop across the resistor changed,
> >just meaning the heater was drawing less current.
> >  I had hooked the scope probe across the O2, and cold there was no output,
> >to be expected, but as it warmed up the output swung toward, .2v.  Just in
> >atmospheric conditions.  Ok, so then it should go way high in pure O2 right,
> >nope went a little over .3, and stopped there.
> >  Did I need to load the sensor?.
> >  The heater doesn't go to a high enough temperature for the O2 to fully
> >swing high?.
> >  Does the engine side need to see a slight amount of pressure to reference
> >to?.
> 
> Bad thing about O2 sensors is they aren't truly O2 sensors... they are HC
> sensors.
> In pure O2, the sensor should keep a low voltage.  In an environment rich
> with HC (IE propane, unburnt fuel etc) they should go .9-1 Volt.

Ok, please splain this statement.  O2 sensor voltage drops when spark
plugs fail to fire, and there's more HC present than when everything's
sparking normally.  Why the contradiction?
Shannen