O2 sensor question

[Chad]

>
>So, do you remember Chad how many wires the sensor you mention above
>had, or if it had an O2 pump? If just the 4, that could explain why the
>careful control of the heater, because ...
>



This is one of the full blown five wire O2 sensors.  If you can get ahold of
the technical information on it from Bosch (Dave: this is where to get the info
you want if they will send it to you), they have some response graphs that
characterize the O2 content based on the current coming from the sensor.  The
bias conditions for these graphs include temperature and reference voltage.
This is why we needed to control the heater so closely (even though it does
have a positive temperature coefficient).  Sure, the heater is self regulating
in that it won't get into a thermal runaway situation, but the drifts in
temperature mess up the accuracy of the measurement relative to the graphs.

Maybe you can teach me a little bit about the terminology.  This sensor either
draws or sources current if the mixture is above or below stoichiometric, is
this what a 'current-pump' type sensor is?

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