Op amping the O2 sensor

[Bruce Bowling]

> The question of the post:  Is the frequency of the GM ECU swinging of
> the mixture back and forth through stoichiometric beyond the frequency
> limit of op amps?
> 
> Joe Boucher
> 

What I have heard is that this "switching" frequency is something
below 10 Hz - an op-amp could easily do this.

I guess the op-amp circuit would be configured as to add an adjustable
DC offset to the O2 sensor output?

Since we are talking O2 sensors, I have a fundamental question about
the operation of an O2 sensor around stoichiometric. Some people have
stated that the O2 sensor puts out a roughly linear voltage as one
mucks with the A/F ratio. Others have stated that the O2 sensor
acts like a hard "switch" at stoichiometric, producing voltage
at one side of stoch and not producing on the other.

Which is it? OEM boxes appear to treat the signal as a switch, but I see
all these gizmos that display the voltage as a variable quantity?
Does the thing possess some sort of "duality"?

- Bruce

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                 Bruce A. Bowling
                 Staff Scientist
   Thomas Jefferson National Accelerator Facility
    12000 Jefferson Ave - Newport News, VA 23606
                 (804) 249-7240
bowling at cebaf.gov  http://devserve.cebaf.gov/~bowling
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