Originally Posted by
dr.mike
A lot like you described. 0.0% would be everything richer than 14.7afr ( lambda 1.0 , or, zero free oxygen )
0.05 to 2.5% would be on the lean side, usually with 2.5% ish only happening on decel.
With the sensor in in open air you get 20.9%, corrected for altitude, barometer reading, and air temp. That's usually in the 19% to 21% range. But doing a free-air-cal will force the reading to 20.8 or so. Hence, using rCal mode.
If the gauge is in AFR or lambda mode, it will display "- - - -" with the sensor in fresh air, instead of 19% - 21%
The analog output never changes functions and is always outputting based on Lambda values.