O2 sensor question

[Garfield Willis]

On Thu, 23 Mar 2000 17:14:03 -0700, "Chad" <chad at dynojet.com> wrote:

>You're right about the reference voltage.  A precision reference voltage is
>applied, the correct temperature is set up, then the resulting current is
>measured.  The control loop is set up to measure the voltage drop across the
>heater to check it's temperature (adjusting if necessary), then measuring the
>resulting current for O2 content.  Technically, I do think I misused the term
>'bias conditions', what I mean to imply are the operating conditions that the
>Bosch graphs are based upon.

Sounds close enough to me, technobabble isn't as precise a vocabulary as
we're led to believe, anyway :); the drift I got is what you've detailed
above, and based on that, it does seem that this sensor, while perhaps
operating on similar principles, has some distinct differences from the
NTKs. Interesting.

>Admittedly, I don't understand what the reference voltage does, I just know
>that it needs to be there.  In the interest of learning, I'm going to try to
>find some more info about the physical construction of this sensor.  It is my
>first guess that the reference voltage is used to extract a given number of
>oxygen atoms from the chamber, and the polarity and magnitude of the current
>needed to pump oxygen back into equilibrium indicates the O2 concentration in
>the chamber.  This is probably a hasty conclusion, but I would really like to
>learn *exactly* what is going on.  Any insight from how NTKs work?

The most detailed info on the NTK sensors is found in their SAE paper
#920234, but I think you're going to find that your Bosch gizmo there
works in a somewhat different manner. Doesn't Bosch ever publish about
devices like this? I don't recall anyone ever mentioning a paper on the
LSMs either.

Gar


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