air/fuel ratio meter

what is the difference between a digital air/fuel meter and the analog ones that say lean and rich on them? how does the digi one read....does it actually show u how many points above norm u are or the percentage lean u are or what...and how does the analog one determine the byas for the nuetral between rich and lean.
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I am not sure about the aftermarket meters but I just picked up a single wire oxygen sensor from the parts store and put it into a bung I had welded into my exhaust.Using my digital volt meter set on the 0-2V I make changes and see what happens.The optimum voltage should be about 500 mv, anything higher is rich and lower is lean but you usually want to run on the rich side.The air/fuel ratio vs voltage curve is very steep around the optimum setting so anything from about 700-300 mv seems to be ok.If you were buying an aftermarket one an analog would probably be easier to watch.
I believe the digital ones give you actual numbers to work off of, where as the analog ones only give you a light spectrum too show where you fall. I could be way off on this, but I believe the analog is a constant reading of rich or lean updated every time the computer makes and adjustment to the ratio; a digital gauge tells you numerically what your average ratio is at a given rpm and engine load, much like the A/F meters on a dyno. Analog gives you a much more user friendly idiot proof red light/green light way of knowing if you're running good, while with digital you have to know what your ideal ratio is and tune the car based on the hard numbers. This is much better for tuning a forced induction or N2O car, since usually you already have an ideal ratio number to shoot for based on your application. Don't quote me on any of this! but that's been my understanding of it.
Actually there are three types.

1. Rich, Stoich (14.7:1) or Lean types only tell you if you are rich, lean or running at Stoich.

2. Analog WBo2 meter which gives an analog output of actual AFR.

3. Digital WBo2 meter which gives actual AFR with digital and some also give analog output as well.

Newer meters like the Innovate Motorsports LM-1 is all digital with datalogging and programmable analog outputs. Check it out at

Good Luck, Don