Re: OXY sensor readings??

[Brad Sheridan <brads@mindspring.com>]

> 
> At 11:29 8/11/97 -0600, Chuck wrote:

> The oxy sensor is actually a small fuel cell - it has a very high
> resistance, and will probably read open if you use an ohmmeter. Full rich
> output is about 1.5 volts, if I remember properly - there's something in the
> manual about using a flashlight battery to test the circuit. You need to use
> a high impedance voltmeter to avoid loading down the circuit - analog
> multimeres will not read what the computer is really seeing, and will cause
> the computer to try to 'fix' the reading by changing the mixture - probably
> much richer...
 
  It reads from 0-1.1V, give or take a little. Yuo don't want to measure
resistance across it, you can potentially fry them doing this, or so I've
been told. The output is very nonlinear, and varies with temperature, and
also age. The main thing its useful for is telling when your crossing from
lean to rich, or rich to lean, as going from one to the other produces a
rather large voltage swing, while trying to use it to determine exact AFR is
difficult due to the variance with temp and age. Here's a link to someones
page who has apparently tested his sensor. Notice that he is doing this at a
constant temperature, and also that the "power" range is still only 50 or so
millivolts.

http://www.students.tut.fi/~k124476/dataBySubject/Oxy.html
 
Brad
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