Wide Ratio O2 meter (my mistake)

[garfield at pilgrimhouse.com]

On 12 Mar 1998 04:36:50 GMT, charlesg at cco.caltech.edu (Charles Grosjean)
wrote:

>Now that I've dug my head out of my rear and found my data sheets, a nice
>engineer at Denso sent me a paper (SAE 970843) a while back describing the
>Denso wide-range sensor used by Toyota. It is used on LEV vehicles starting
>in 1997. It comes in a standard 4-wire package and is the same cost as a
>regular Toyota part (sorry, don't have any #'s). To operate it, a fixed bias
>voltage is applied, and the bipolar output current is measured (+ve lean, -ve
>rich). To light it off, full power is applied, and then the power is reduced
>once the substrate is up to operating temperature.

I really wish you'd make more mistakes like that, Charles, if it means
we get another good reference whenever you bethink yerself. Thanks! Heh.
Actually, I too thot it was the heater impedance at first.

SpeakinOheaters, I fired up my NTK heater (yes, I had a goodly airflow
around it just in case it was gonna fry itself). It measures 3.4ohms
cold, but the current rapidly comes down to around 1.4A as it heats up
on 12V applied, which is where the current settled for over a minute,
after which, not being one to be in a hurry to overcook a $130 burger, I
shut it off.

I was extremely PLEASED with the result; in fact I grinned from ear to
ear. Wanna know why? Cuz that fathead that told me it would take 5 years
to figure out, the one building combustion controllers, I happened to
ask him what kinda power his Lambda meter required, and he said "less
than an amp". Soooooo, that tells me that the heater supply ISN'T part
of the control loop. Oooops, guess he gave away part of the secret. Hee.
Nice not to have to modulate several amps.

More eXperiments to come.

Garfield