[Diy_efi] WB O2 system

[Bernd Felsche]

</lurk>
Garfield Willis tapped away at the keyboard with:

> On Mon, 10 Jun 2002 12:52:29 -0700, Dennis Gearon <gearond at cvc.net>
> wrote:
> 
> >What does 'wide band' mean anyway?
> 
> A "marketing term", not originally used by the developers of these
> sensors able to measure AFR/mixture, but introduced later as an
> aid to distinguishing between the 'switching' type sensors that
> can only be used to detect either lean-of or rich-of
> stoichiometric. Over time the O2 sensors that could measure wide
> ranges of AFR well-lean and well-rich of stoich, came to be called
> 'WB' and the standard emissions O2 sensors that could only detect
> stoich crossings came to be called 'narrow band' or NB sensors.

Nit-pick: The sensors' output voltage is a measure of the ratio of
partial pressures of oxygen. AFR can then be approximated if you
know the fuel type and the relative pressures of exhaust and
reference gases.  The sensors don't measure AFR. If you're unsure of
the fuel type (usually the case at the consumer end), then it's more
sensible to use the normalised ratio of AFR to stoichiometric,
denoted in the technical literature with the Greek letter "lambda".

> Originally, the term used by mfgs of these sensors was "UEGO", or
> 'universal exhaust gas oxygen sensors', and were originally
> focused on lean-side measurement for lean-burn vehicles, but
> probly because the term wasn't very descriptive and also was
> harder to communicate, 'wideband' or WB has caught on now in the
> trade. Somewhere in this timeframe, IIRC Bosch also introduced the
> term 'lambda sensor' to ID the WB sensors it was developing.
> Besides, most Euro's talk in lambda's rather than AFRs.

Bosch used the terms "lambda sensor", "Lambda probe" and "Lamda
Sonde" for a long time before WB. AFAICT, they've always referred to
it as such.

<lurk>

-- 
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