DIY-WB... It's alive...

[Bernd Felsche]

Bob Wooten tapped away at the keyboard with:

> If I am not mistaken an O2 sensor is a voltage generating device.
> this is why you can "test" them with a meter & not have an ECM
> connected to them (the standard zirconium switch types, I am still
> out in the weeds on the ION pump, WB type).  My understanding is
> also that this is part of the reason why they fail.

The O2 sensor (Nernst cell) is a voltage generating device. A
wide-band ion-pump cell consists of two main parts; the ion pump
cell and a (measurement (Nernst) cell; the latter operating on the
same principle as a narrow-band cell, but exposed to ions
delivered/removed by the pump cell, instead of the exhaust gas
itself.

If the pump cell is not operating, (nett pump current zero) then the
measurement will be very similar to a narrow-band cell, but probably
slower.

The whole point of a WB controller is to maintain that magic voltage
level at the measurement cell by varying the pump cell to either
draw O2 ions into the measurement cell, or to draw them out. The
current required to maintain that balance is then an indication of
the O2 concentration and hence lambda.

-- 
 /"\  Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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