I am looking for a very small liquid level sensor.  It needs to fit in
a very small trough about 2" long, 1/8" wide, and 1/2" deep.  It needs
to be chemically resistant (Teflon or PEEK) and I would prefer TTL. 
Shimadzu has a small leak detector on their HPLC pumps that has about
the right form factor.  It could be conductive, optical, or
machanical, but it has to be small.

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Request for Question Clarification by tutuzdad-ga on 04 Aug 2004 12:40 PDT

CLARK SOLUTIONS has PEEK liquid level sensors in a varieity of shapes
and sizes which measure point level or continuous levels. They have
sensors, transmitters and complete systems. Only you will know best
which will likley work for your project. I recommend you take a look
at their products to try and find one suitable.

ABOUT CLARK SOLUTIONS
http://cmpmedia.globalspec.com/Clark?VID=134989

Navigate down the right side to "Level Sensors - All Types". Click the
link and you'll find a product search engine. My initial search
returned 121 sensors.

I'd be delighted to know if this method works for you and results in
your finding a suitable sensor.

Regards;
tutuzdad-ga

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Clarification of Question by gregori-ga on 04 Aug 2004 21:57 PDT

There are a number of vendors that sell these types of sensors.  They
are primarily for industrial uses.  They mount with 1/4" or larger NPT
fittings.  That means they are close to 1/2" in diameter.  I am
looking for something smaller, ~1/8" in diameter, that will match more
closely with the dimensions of the trough I described in the original
question.  I don't need continuous level detection, just point
detection.

Have you considered making one yourself? The TTL could be external I
presume. Parts can be protected by heat shrink PTFE but does the
egress have to be sealed? This is tricky with PTFE.

Perhaps a thermal bridge. Or conductivity with platinum electrodes if
the liquid is suitable. Capacitive systems are reasonably simple too,
wrapped round a crystal controlled PLL. Lots of other ways to build it
yourself but I don?t have sufficient info to recommend.

Best