Wide Ratio O2

[garfield at pilgrimhouse.com]

On Thu, 26 Mar 1998 21:37:57 -0600, Steven Gorkowski <kb4mxo at mwt.net>
wrote:

>I do not get it, if I do 12 bit A/d conversion dividing the it into
>4000+ pieces from 0 to 1v  and make a table so the table relates to A/f
>ratio and compensate for temp. buy reading with therm. probe . Tell me
>how the reading can't be accurate.

Begs the question, dude. Most/all of them "el cheapo" meters are neither
calibrated nor temp compensated. Thas THE problemo. I want you to take a
look at a perfect example of an "el cheapo" sensor/box at:
	http://www.splitsec.com/ego1/ego1ds.htm
Scroll down far enough and you'll see their so-called "calibration"
curves for their sensor/box. There are three curves show there, for
750degF, 1200degF, 1500degF, all very likely EGT temps observed in use.
OK, now let's pick an example; we'll use yours of wanting to obtain max
HP, which would be on the rich side of stoich, so look at the graph, and
see what you read as far as AFR, if the sensor is outputting say 0.9V.
Well, the AFR is either 12+, or 13+, or 14, depending on the temp!
Somehow I don't think this is quite what you were hoping for, in terms
of accuracy!? They don't have and so can't offer ANY data on
determining/calibrating what the temp of the probe might be, nor are
they implying that they even assume you'd be monitoring the ex-gas temps
with a t-couple. I know this firsthand, because I talked to the designer
for over a half-hour about his 'box', playing ignorant, and asking how I
could use his device to actually MEASURE AFR. His final comment was,
don't get too hung up on the AFR numbers; they're only "representative".
Heh. Yeah.

So yes, IF you use a fine grain transfer function, AND you map sensor
output Vs to AFR, AND you map them along with measured probe (not even
just EGT) temperatures, then YES you'll have a *measurement* instrument.
But I dare say you won't find any of them el cheapo $100-$250 boxes that
begin to meet ANY of them "IFs". And remember, my comments and your
reply were in response to someone asking about using such an el cheapo
to measure AFR, so I don't think I'm addressing a straw man. N'est ce
pas?

Garfield