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From: n295vv@aol.com

Thirty years ago, or so, I invented an auto refill container system for use in
the semiconductor industry.  The system involved two optical sensors-one for high level and one for low
level--that would be wetted by any liquid, including gasoline.  They looked
like pencils.  When the tip of the point was wetted by the liquid, an infrared beam pointing
down the axis of the rod would be reflected back up the axis, and was detected
by an infrared collector.  When the rod wasnt wetted, the emitted beam would
not reflect back to the collector sensor.  The rod sensors were sealed into
the unit with a stainless fitting and were sealed with tefzel compression
fittings.

The pointed rods could be made of any optically clear material that would
allow IR beams to pass through but would be inert to av gas.  A simple logic
system was used to autorefill the container that was being sensed.  They were
very safe--nothing electrical was in the inside of the container, and the
external sensors were extremely low voltage diodes.

Perhaps this system or its components are currently on the market, and can be
modified--look around.

David Jones
Pecatonica, Illinois