Modifying O2 output

[CICIORA STEVEN JOSEP]

On Wed, 27 Sep 1995, Zublin, Bryan (SD-MS) wrote:

> 
> It depends on the output impedance of the O2 sensor.  Try a 100K ohm load.
> If the voltage drops significantly, then I would go with an op amp with a
> high impedance input.  Personally, I would use the op amp always; this also
> allows you to easily add some lowpass filtering.
> 
> Bryan Zublin
> bzublin at gi.com
>  ----------
  I think I remember reading somewhere (this list?  the hotrod list?) 
that one way to get a little bit more liniarity out of an 02 sensor is to 
apply (something like) 0.6 v to it and measure the current into or out of 
it.  I also seem to remember seeing a circuit that will switch a load 
resistor (or two) accross the output of the o2 sensor.  Since the output 
impediance of the O2 sensor is dependent on temperature, mabe this was a 
way to see if it was warmed up, or to measure exhaust temperature.  I 
always thought that a ballpark way to measure exhaust temperature might 
be to measure the current going to the heater (on heated O2 sensors, of 
course).  
  Anyway... if the above two situations are the case for you, than a 
voltage divider wont work.  I know you said not to ask, but what are you 
trying to do?  I've thought about what you mention, and I'm not sure you 
can fool the computer into thinking that it is a little bit leaner than 
it really is.  From what little bit of looking I've done at the output of 
O2 sensors, it is usually much above .6 (.7?) volts (like 1 volt) or much 
below (like .2 volts).  Almost like a switch.
  Hope I provided more insight than confusion!
-Steven ciciora