Posted for "Mark R Steitle" <mark.steitle@austin.utexas.edu>:

 Gary,
 I'll try this again.  For some reason all but the first sentence was
 deleted.
 
 Mark

[ sorry... editor's mistake -Rob@Logan.com ]

Gary,

The ELS-1100 sensors retail for about $95, but I got in on a one time
ebay buy for considerably less, but didn't get to select the model, and
ended up with the 5v model.  If I were buying retail, I would definitely
get the "wet" 10-32v model.  They have three wires, a pos, a neg, and an
output. The output changes to positive volts (check spec sheet for
actual output voltage/amperage) when above/out of the liquid, and OFF
when submersed. I hooked this lead directly to an LED on the panel.  To
run a high amperage device like a fuel pump, it would require a relay as
the sensors can only handle a minimal amount of current (I think it is
40ma).  One of the solid state Powerlink Jr. relays from Perihellion
Design would probably work nicely.  The instruction sheet gives some
examples of how these are hooked up for different applications.  Neat
little device.

Mark Steitle