Wide Ratio O2

[garfield at pilgrimhouse.com]

On Fri, 27 Mar 1998 22:15:18 -0600, Steven Gorkowski <kb4mxo at mwt.net>
wrote:

>Thanks for this information I needed the graphs to make a standard O2
>sensor work and you and this company gave me this information. I have
>used a standard O2 sensor in the past but without temp regulation and
>temp sensing and agree that it is not as accurate as I need but if the
>uC(pic) can regulate the heater so it is close to a temp curve . I can
>build a meter for under $100 and will output A/f ratio to a standard
>rs232 port.

Hey Steve.

Say, couple things I just thot of. First, them SplitSecond guys claimed
the sensor they sell (graph shown) is a somewhat "wider-range" (for a
cheap heated sensor) than usual, that's made by NTK! You might wanna
sniff around with them about that. If you made it clear that you weren't
interested in their box, but only their sensor, and wanted to know a
second source for it, they just "might" be willing to share that info.
Maybe sell you one sensor (I think their price is $60 or so), with the
understanding that they'd give you the automotive source if you needed
to second-source it. Point is I'm not sure those curves are
representative of any ole heated O2 sensor. Might wanna check on that.

Second, you bring up a good point, in that if you used the "sense the
sensor's resistance" technique like Peter has illustrated, and just held
it fairly constant by controlling the heater current (meaning the
element's temp was fairly constant), then FOR THAT SENSOR, if you could
run it *just once* in league with a previously calibrated O2 Meter and
calibrate your own Vs versus AFR, even if you didn't know the
temperature exactly, nor had the temp. calibration curves, you could
still get the thing calibrated decent and repeatable enough. You don't
necessarily need to know the temp. precisely if you have some other AFR
calibration standard to use, as long as you know you can control/keep
the sensor at that calibration temp. from then on, after the calibration
run is over.

I hate to see you go to all this trouble, though. Maybe if you can wait
a couple more weeks, we'll know if these NTK UEGO sensors are gonna work
out. Yeah, the sensor is more moolah ($120 vrs. $25-60), but if they
work well, the electronics will be not much more than a few bucks on top
of that, and the thing might be self-calibrating (free air std), taking
away the need to borrow some other standard against which to calibrate.
But hey, if you can make the calibration & heater control of a ordinary
heated O2 sensor give 0.5 AFR accuracy, maybe we build one snazzy $200
one that's self-calibrating, and then loan it around to calibrate the
<$100 ones. Hee hee. Kinda a pyramid scheme.

Either way, though, it's looking much more positive that we'll get
something, one way or another, to give us some better O2/mixture/AFR
readings. This has been a nice productive thread so far; lots of good &
diverse ideas, dudes.

Gar