Monitoring O2 sensor/voltage

[R & C Webb]

Guys -

One of us is TERRIBLY confused!

A normal O2 sensor is a device with an OUTPUT of ~.5v at stoich,
swinging above and below that but with that as an average. No
voltage is applied. The voltage is GENERATED by the sensor from a
chemical reaction with the oxygen in the exhaust.

"Fuel Injection"
Jeff Hartman
Motorbooks int'l
Page 45

gives a good overview.


Zack wrote:

> Bruce,
>
> Actually, the way I understand it from what's been said, ~0.45
> volts is
> applied to the sensor through some large resistance (~1
> megohm).  The
> resistance of the sensor when cold is extremely high, it's
> basically an
> open circuit, so the ECU sees steady ~0.45 volts as long as the
> sensor is
> cold (or if there's an open circuit caused by a faulty
> connection or
> sensor).  Once the sensor heats up, its resistance drops to a
> value much
> lower than that 1 megohm, and it also starts generating a
> voltage
> proportional to the O2 in the exhaust, so the voltage the ECU
> sees at that
> point is basically just the voltage generated by the sensor
> itself.
>
> Zack
> ----------
> > From: bruce plecan <nacelp at bright.net>
> > To: diy_efi at efi332.eng.ohio-state.edu
> > Subject: Re:Monitoring O2 sensor/voltage
> > Date: Monday, February 23, 1998 1:43 AM
> >
> > I'd appreciate a little clarification, on this GM O2 sensor
> monitoring.
> > If all they did was measure the output from the sensor, then
> I could
> > understand that it was just reading the voltage.  But, by
> appling a
> > voltage to it, and it having to develope enough current, and
> voltage
> > to alter that signal doesn't that change what the ecm is
> monitoring
> > from straight voltage, to wattage?..
> > TIA  Bruce    Further documentation of why I own several cone
>
> >                      shaped hats...