EGO clogging.

[Dale Ulan]

> 
> i/  We all know the 'characteristic curve' of an O2 sensor, but how much
>     effect does the actual exhaust temperature have on it's accuracy,
>     and also does a HEGO have some way of regulating it's temperature?

Most HEGO's I've seen hook up to +12v, and they use the positive temperature
coefficient of the heating element to regulate the temperature.

EGO sensors aren't affected by temperature much for its real 'trip point',
but temperature is the largest contributor to voltage variations in the
sensor. GM tends to use the voltage level out of the sensor for more
than just 'RICH/LEAN', so they use various compensations to predict
the O2 sensor temperature.

> ii/ What about electrical effects changing the sensor's voltage? eg
>     thermocouple effects between the exhaust and the engine. Should
>     the sensor be used in a 'balanced' set-up.

Normally, between the block and manifold there's little difference. GM
attaches one end of the diff amp (- end) to the engine ground. The
other end goes to the O2 sensor. The - end should go to a good engine
block ground.
The LM1964 is an amplifier designed especially for amplifying O2 sensor
signals. It's in National's special purpose devices book (Linear 3).

-Dale