WPSLPGExhaust Gas Oxygen (EGO) sensor Information

[Chris Conlon]

At 11:59 PM 8/2/00 -0500, Tom Meagher wrote:

>Oscillation duty cycle, averaged with a low pass filter to produce a DC
>voltage is evidently the operative parameter.  Perhaps you could sample the
>signal with the PIC and do FFT's on it to produce additional information to
>better characterize AFR.

If all you wanted was an average AFR over a few seconds, go ahead.
It's a waste of time imho. It still won't be any more *accurate*
than an instantaneous reading due to the sensor's output being so
nonlinear, and varying with EGT, backpressure, etc, none of which
are compensated for by any amount of averaging over time. You'd be
averaging over many many cycles, slowing response time greatly,
and gaining nothing in the bargain. 


>Does anyone know the physics behind the oscillating output?

There's no physics of it, that's the ECU adjusting AFR to try and
maintain stoich, aka closed loop operation. Look at the timebase
on the scope traces. The sensors can show some interesting things
at much higher bandwidths, but those traces are not showing any
of them.

Really this has all been beat to death in the archives. People
are almost lucky Gar is away for the moment. I can easily see
him dispensing a brace of new bodily orifices when he returns.
(And if you think I'm exaggerating, you haven't been reading
the archives enough.)

   Chris C.

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