o2 meter

[Tom Cloud]

>Andris Skulte wrote:
>> 
>> I just built the 10 LED O2 meter today (
>> http://www.students.tut.fi/~eppu/dev/EGO-bar.html ), and it worked great
>> on the testbench. There was a note in the instructions that I should
>> ground it only at the o2 sensor. What is the best way to ground it
>> there? 
>
>No what they mean I think is that it needs a VERY good earth. A direct
>connection to the Neg terminal of your battery works - at least it works
>well how I have done it. The sensor will ground out through the engine -
>it has a very good connection to the battery ground, via the engine
>earth strap.

no, the "earth" / "ground" connection is for the power source.  In
any circuit you need a minimum of two wires for power and two more
for signal.  Many times the signal return and the PS common are
combined (single-ended input).  In this case, it's obvious that
there must be a floating input whose porpoise is to eliminate
false readings due to circulating "earth" currents.  Connecting
his signal return to the battery would probably make this situation
worse, not better.

Tom Cloud

     A truly wise man never plays leapfrog with a unicorn.