Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!ubc-cs!alberta!calgary!!smit
From: smit@.ucalgary.ca (Theo Smit)
Newsgroups: sci.electronics
Subject: Re: Oxygen Sensor Info Needed
Message-ID: <1772@cs-spool.calgary.UUCP>
Date: 31 Aug 89 19:25:57 GMT
References: <9187@attctc.Dallas.TX.US>
Sender: news@calgary.UUCP
Reply-To: smit@eneli.UUCP (Theo Smit)
Organization: U. of Calgary, Calgary, Alberta, Canada
Lines: 44

In article <9187@attctc.Dallas.TX.US> robp@attctc.Dallas.TX.US (Robert Parnell) writes:
>
>Recently I saw an ad for an oxygen sensor that is used to adjust the air/fuel 
>mixture for an internal combustion engine.  It had a sensor that mounted in
...
>idea behind the device is that with a lean mixture more oxygen will remain in 
>the exhaust gases than with a rich mixture.
>
>The sensor that mounts in the exhaust system is a standard automotive part
>used in electronic fuel injection systems, and it's my guess that the small
>box is nothing more than an ohm or volt meter with bar graph display.
>
>What I need to know is the electrical characteristics of the oxygen sensor.
>What's the resistance or voltage output of the sensor when the fuel/air
>mixture is correct (which I believe is 15 grams of air to 1 gram of fuel)?
>
>Robert Parnell
>robp@attctc

Sounds like you're talking about the MicroDyno (I can't remember the mfg's
name). 
A standard automotive oxygen sensor has an active metal in a shroud which
sits in the exhaust stream. Free oxygen causes the sensor to produce a
potential difference between the case and the center lead; basically
it works like a battery. The active range for the sensor is from about 13 to
1, to 15.5 to 1. (I'm doing this from memory; a friend uses one of these
to set up the mixture on his turbo Corolla), with the output voltage range
from 0 (rich) to 1.0 V (lean). I think that at stoichiometric (14 to 1) the
output is about 0.6 V; the curve is not linear. The transient response of
the oxygen sensor is pretty good (in the tens of ms, I believe). 

The major problem with the unit is that using leaded gas (such as 100-130
aviation fuel :-) fouls the sensor and makes it unusable after some time.
Also, while 14 to 1 gives maximum efficiency and minimum emissions, this
is too lean for maximum power output. The air/fuel ratio for maximum power
from gasolines is around 12 to 1, which is outside the sensing range for
the device.

Still, the MicroDyno has proved a valuable analysis tool for carb jetting,
especially for getting rid of those part-throttle bogs.
Disclaimer: I'm not affiliated with the manufacturer of this thing, I've
only seen it used. Your mileage may vary.

Theo Smit