No.  The airliner had wires passing through the fuel tank inside a metal
conduit.  The wires shorted and generated enough heat to ignite vapors in a
nearly-empty tank.

UL has rules for "explosion-proof" circuitry, which basically intends to
ensure that it can produce no sparks and can't carry enough current to
generate enough heat to ignite anything.

It's not all that hard to meet the requirements.  As I understand it, just
about anything powered by a couple of AA batteries will pass the tests.
Basically you're limited to about 3 volts, any current source must have at
least enough internal resistance to limit current to a few milliamps, and
there's a minimum spacing between exposed conductors such as PC board
traces.  I wish I could quote you exactly, but I don't have a written copy
of the spec in my possession.

> -----Original Message-----
> From: Olin Lathrop [mailto:olin_piclist@EMBEDINC.COM]
> Sent: Friday, September 21, 2001 11:34 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: Conductive Liquid Sensor
>
>
> > As long as the connections are tight and there are no
> sparks, it doesn't
> > matter if you run electricity in a fuel tank.
>
> Yes, that's what's *supposed* to happen.  Unfortunately this
> kind of setup
> leaves a lot less margin when something goes wrong.  Isn't
> this exactly what
> brought down that airliner near Long Island a few years ago?
>
>
> ********************************************************************
> Olin Lathrop, embedded systems consultant in Littleton Massachusetts
> (978) 742-9014, olin@embedinc.com, http://www.embedinc.com
>
> --
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>

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