WB free air calibration

[bcroe at juno.com]

If you really want to be sure, get the calibration gas.  But 
the WB circuit utilizes the calibration resistor built into 
the sensor to get pretty close.  You should be right on
at stoich, increasing error as you get away from that 
point.

If you want to use air calibration, the Ip currrent (or Vout
deviation from stoich) in air should be about 3 times the
current at an A/F of 21.5:1 or 22:1.  I actually reduce the 
Ip sense resistor (and Vout deviation from stoich) by a 
factor of three, so that the air test will fall onto the lean 
end of my LED display.  You might note that on the pictures
from a while back.  Just use a pushbutton to parallel
the 100 ohm R28 with a 50 ohm (or a couple more 
100 ohms).  Tested this on 3 sensors so far.

Bruce Roe

On Wed, 31 Oct 2001 01:55:05 -0800 "Lowell Foo" <lowell at smartt.com>
writes:
> How do most of you guys do sensor calibrations?  What do you
> use for an assumed oxygen % in the atmosphere?  (or should I
> be buying calibration gas?)
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