Monitoring O2 sensor/voltage

[garfield at pilgrimhouse.com]

On Mon, 23 Feb 1998 17:28:06 -0900, R & C Webb <cwebb at polarnet.com>
wrote:

>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.

>Zack wrote:
>> 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.

Nope, NO confusion. This is one of those rare occasions where you're
both in "violent agreement". He was just saying a high Z bias voltage is
applied to this battery-come-lately, so when it's warm and functioning
correctly, the bias is outta the picture and the O2-sensor battery, now
a low Z source, is running the show. No conflict.

Garfield