Wide Ratio O2

garfield at pilgrimhouse.com garfield at pilgrimhouse.com
Thu Mar 26 02:04:25 GMT 1998


On Sat, 21 Mar 1998 15:33:24 -0800, garfield at pilgrimhouse.com wrote:

>Bottom line practically speaking is that the ... [thread] ... was
>assuming using the stock Honda sensors available for $120-130US at any
>Honda dealer.

Hey maties.

Got time for another DIY_EGOMETER update? B)  Well, here it is!

Frank "mad scientist" Parker (say, Frank I was just wondering, are you
at all related to Bonnie Parker, by any chance?) has been conducting
eXperiments on Egor (er, I mean UEGO) in his lab, and has made some
interesting discoveries.

First the good/grand news: we think we've just about completely figured
out how the circuit in the NTK box behaves, and why. The earlier mystery
of the un-spec'd current forced into the measurement cell appears
solved. Frank even discovered this cute lil procedure it does when
warming up to prevent bogus ion pumping (otherwise, whilst warmup'ing,
the sensor thinks it's measuring a way rich mix; my guess is this dance
is to prevent damage to the sensor from excessive ion pumping during
powerup). The box takes the sensor through a 'rite of passage' through
stoich to make sure it's "gone galvanic" before it turns on the pump.
(Not to worry, we *have* the technology).

Now the bad news: well, maybe not reeeal bad. Only that the sensors that
NTK uses with their box don't in fact appear to be the same ones as the
Honda OEM sensors. Almost all the markings and outward appearance are
the same, including the connector, but the CAL resistor values are an
odorOmagnitudi different! So we have that one 'small' mystery to sleuth
out, but other than that, it's lookin real swell, dudes. This weekend
when I get back from corporate charm school, I hope to pump some ions
meself, with a test apparatus, using std Honda OEM sensors, and we'll
have more news after that.

It doth still appear the circuit to pull this off will be eminently
KISS-worthy, cheap, entirely analog, and self-calibrate-able in free air
(just like the big boys Horiba & NTK). But let's wait and see; it's a
tad early to be clinking the glasses together and yelling "cheers", but
we ain't far off now, methinks. Once we have a working lab circuit, I'll
post it to the ftp site, and we can all tear it apart, critique it, and
make it even better groupwise.

Garfield




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