O2 Volts

[Orin Eman]

>   The useful facts as I see them are:
>   In cold weather, a none heated O2 sensor can go open loop. due to the O2
> sensor being too cold.  A heated O2 develops enough heat so that it can
> "properly sense" the needed gases to operate.
>   The O2 sensor, as tested responds to HC rather than O2.
>   While you might be able to change things, or define other operating modes,
> I know that if I mount the sensor far enough away from the engine that being
> heated is neseccary, then I know what gases matter, and thus what the sensor
> is seeing.

There are a couple of things I'd like to throw in the mix here.

The heater on the heated sensor is a helper to get the sensor up to
temperature... it's probably still relying on hot exhaust gases to
be at working temperature... it may not be hot enough when testing with
room temperature gases.

There is a catalyst on the electrodes which may well promote the
combustion of gaseous hydrocarbons with the O2 that diffuses thru
the sensor, hence the reaction to gaseous hydrocarbons.

The sensor itself, when hot enough senses the relative concentrations
of O2.  This is not necessarily the O2 concentration in the exhaust
gases as measured by other means due to the catalytic action of the
sensor electrode...

Orin.