Trevor Boicey wrote:
>
> Barry Schwartz wrote:
> > I?m considering setting up a fuel/air ratio meter using a digital
> > voltmeter (0-1V), and a Bosch oxygen sensor. How does one connect the
> > sensor up. Is one lead just connected to a switched, positive side of
> > the battery, and the reading taken from the center lead and a ground?
>
> If it's a standard "one wire" unheated sensor, just read the voltage
> off the wire, the unit grounds itself in the exhaust manifold.
>
> > Or is some additional wiring required? - I haven?t got the sensor yet,
> > but plan on buying the universal, unheated sensor. I can?t see spending
> > $150 for a 0-1V led readout just to test fuel/air readings, and once set
> > have it sit on the shelf! Any of you wizards out there have any ideas?
>
> It's VERY difficult to read with a digital multimeter. The actual
> range of the unit is very nonlinear, the computer uses the number of
> "lambda crossings" to determine if the unit is roughly centered.
>
> It's confusing, but instead of the unit outputting 0.5V at correct,
> it will oscillate from 0.2V to 0.8V when correct, spending roughly
> half the time at each. Too rich or too lean and it will spend much
> more time at one end and cross the middle less often.
>
> With a fast sampling meter you just get unreadable noise, with
> a slow sampling meter you get somewhat random samplings that are
> hard to correlate.
>
> --
> Trevor Boicey
> Ottawa, Canada
> tboicey@brit.ca
> http://www.brit.ca/~tboicey/
This is where us old timer electronics wizzards still use a analog
voltmeter. It's a lot better for reading varying levels as it tends to
average them out a little. I love my high dollar modern goodies but I
still keep a couple of oldie goldies around for real work.
Joe Worsley
80 TR8
72 TR6
Tupelo, MS
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