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[rr]

All opamps have an input bias current. The question has been
"is the O2 sensor input biased to 450mV, on purpose?" In
other words does the sensor have a 450mV bias output from
the ECM to the O2 sensor?

I have not found any evidence that it does. I'm thinking that
what folks are seeing is the 'home' position being read by the
ECMs ADC & reported as 450mV. This is with the sensor
disconnected, hence a bias must be being applied to the sensor.

BobR.


Ludis Langens wrote:

> rr wrote:
> >
> > The spec sheet for the LM9044
> > makes no mention of a bias voltage output to the O2 sensor.
>
> The data sheet I have does mention a bias.  Check the spec called
> "Non-Inverting Input Bias Current".  The typical value is +/- 380
> nanoAmps.  (In other units, 0.00000038 amps.)
>
> > With a Fluke 83 measuring this input to ground the ECM then reports
> > a 409mV O2 sensor voltage. The Fluke reports a 397 mV level
> > on the O2 + input (open). This is quite a change for a high input
> > impedence DVM.
>
> Measure with the meter connected between the + input and the ECMs 5 volt
> supply.  Or measure between the + input and the + end of a D cell (or C,
> or AA, or ...) with the negative end of the cell jumpered to ECM ground.
>
> --
> Ludis Langens                               ludis (at) cruzers (dot) com
> Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
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