Wide Ratio O2 meter (my mistake)

[Charles Grosjean]

Frank F Parker <fparker at umich.edu> writes:

>The heater circuit/resistance does not matter. It is the other 2 wires,
>the sensor, that we have to measure the internal resistance of without
>upsetting signal output.

Oops, I fired off a response based on memory to find myself wrong. From the
data sheet "The latter {ceramic temp} is determined by the output impedance
of the sensor."  My bad. Depending on the impedance, I suppose you could also
measure the impedance by superimposing a small AC signal which could be easily
filtered out downstream.

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.

All the engineers I spoke to were Japanese, and I suspect some knowledge of
the language would have helped get some more technical info across.
NGK is at 810/926-6900 and ND is at 810/350-7500. NGK was not very helpful,
especially after I mentioned the word "car" and suggested I talk to Horiba.

Charles