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

[Ludis Langens]

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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