On Mon, 09 May 2005 00:50:37 GMT, "Roger Long"
wrote:

Well, I've decided to go even higher tech. For just ten bucks more
than the SansSwithc that West Marine had, I've ordered their See Water
switch. This is a capacitive switch that is height adjustable so you
can fine tune the cut off level. The thing that sold me about it
though is that it doesn't sense oil or fuel. That way, if the fuel
tank springs a leak or a fuel line breaks, the bilge system won't pump
the whole mess overboard. Even if you have a lot of fuel oil floating
on top of the water, it will pump out the water and stop when it hits
the oil. Having seen the havoc of automatic bilge pumps emptying fuel
tanks into the harbor, I think this ten bucks is good insurance.

That's the theory anyway. I'll let you know how it actually works out
///

Capacitive sensors are often used in aircraft fuel tanks as level
sensors. Here, the presence of water is a real nuisance because the
dielectric constant of water is about 80 and that of fuel is in the
low single digits.

So for water sensing, this disadvantage looks like a real advantage.

Brian Whatcott Altus, OK