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RE: Oxygen Sensors used in EFI systems

> -----Original Message-----
> From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
> Behalf Of Murray Peterson VK2KGM
> Sent: Friday, February 16, 2001 8:09 AM
> Subject: [amsat-bb] Oxygen Sensors used in EFI systems
> I know this is not exactly a satellite related subject but I 
> was wondering whether there is anyone on this list who 
> knows (from an electronic point of view) how an Oxygen 
> Sensor works. Is it a variable resistor of sorts? Do you
> apply a constant current to it and measure the voltage 
> across it?

Good morning Murray,

	It depends on which model you have.  We use
passive devices.

	Although a bit away from automotive use, we use
not only oxygen sensors, but other similar devices in the 
monitoring of pollution.  Here is how it is done.

	The device has two thermisters in it.  One is a bare
thermister.  The other is coated with a chemical that reacts
to the presence of the pollutant we wish to monitor.
(oxygen in your case)

	The bare thermister acts as the reference, telling us
the overall sample temperature.  The coated thermister
shows a higher (or lower) temperature because of the
presence of the pollutant.  By using known test samples,
and developing a calibration curve, you can determine the 
level of pollution for a given output.

	This is but one way, and a simplified way at that.
I do not remember the coating chemicals in my head, nor
the resistances of the thermisters, nor the temperature
coefficients.  Heck, 0600 on a Friday morning, I would
not remember my name, except that it is in the signature
block below.

	Hope it helps.


My E-mail address: mailto:kd9kc@elp.rr.com
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yourself, or dial  9 1 1  and maybe wait the rest of your life.

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