Ohm's law, O2 Sensor testing and Air/Fuel Meters - Saab 9000 Bulletin Board - Saabnet.com
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Ohm's law, O2 Sensor testing and Air/Fuel Meters
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Posted by TRJ (more from TRJ) on Sun, 19 Oct 2003 18:41:30 Share Post by Email
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Since I'm now admittedly paranoid about everything, I thought I'd try to better understand the O2 sensor feed and its relationship with multimeter testing and the implementation of an Air/Fuel Guage.

Confusion #1
A 3 wire O2 sensor has a single wire connection to the ECU while the other two are used to heat the unit. Is there a shared ground across the unit somewhere? How does the data get there? It has been a long time since HS Physics and I'd rather ask and seem stupid than spend the time to find out on my own. I'll guess that the bung connection on the pipe is the ground.

Concern #1
Obviously electrons are being excited along the signal wire. Does the attachment of a multimeter with a path to ground effect the voltage being received by the ECU?

Concern #2
If I put a permanent A/F meter in a parallel path to ground, is the ECU reading affected? What good is it if that is the case? Is there a certain threshold of acceptable parallel path?

Last question:
Has anyone tried one of those DIY A/F meters? I've found a few compelling designs using a google search using "building an air-fuel meter"

It's never too late to teach an old dog new tricks.
TIA








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