Oxygen sensors

[John S Gwynne]

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   In message <9411031452.AA24175 at coulomb.eng.ohio-state.edu> , you write:
 
| How I saw it done in the controller in the 1991 GMC pickup truck
| is the O2 chip has an internal voltage divider that places the output
| of the O2 sensor at 0.450 volts until it warms up. Once its internal
| resistance drops below a certain point, the size of the O2 amplitude
| indicates primarily temperature.

ok, so if its cold the output voltage stays between, say, .3V and .6V
for an extended period of time. Once it exceeds these thresholds, we
declare it's hot enough to use.

If we aren't trying to meat emission standards, I suppose a simple
warmup period is enough. (?)

| The O2 amplitude is used in several tables to operate a PID controller.
| Airflow is also used in a few tables. I was surprised, but the D term
| appears to be used... and I've never seen it referenced in any papers
| I've read.

If the amplitude primarily indicates temperature, wouldn't a
correction based on expected temperature have to be applied *before*
a PID controller? I imagine that is, in part, what the tables
do. Can you give us a better description of the tables?

What do you think of the approach of just hard-limiting the sensor
output once it warms-up and integrating?

Do the PID coefficients look like it's dominated by I?


                                       John S Gwynne
                                          Gwynne.1 at osu.edu
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