Doug/Barry,
Why not use some of these GEMS electronic fluid level sensors.  They

are

totally solid state.  They use an infra-red beam reflecting off a

prism

type lense.  When submerged, the light beam is disbursed, when above

the

liquid, the beam is reflected back to the IR receiver and a signal
is generated.  I put one in each of my wing tanks at the 6 gallon
level

as

a low fuel warning.  They are connected to two "Low Fuel" LED's on
the panel.

Mark S.

Mark and Doug,

Your suggestions make sense, however, in the attached picture, you
will see my wing with the leading edge fuel tank.  Of course the view
is not that good as it is from the aft, you can see the ribs
separating the main tank. I believe these are for stability and to
keep the fuel from sloshing too much in the tank. How would you apply
your suggestions to this scenario? I like both suggestions, the laser
sensor and the magnetic tube, but I am not sure that it will work in
my situation.

Thanks,


Barry,
Short of drilling through the spar, I don't see how you could use the
GEM sensors in your application.  And yes, they run about $100/ea
retail, but I got mine off ebay for much less.  There are some
microchips for sale on ebay now that are meant for monitoring liquid
levels.  You could use these in a similar manner as the GEM sensors
by running wires to various spots in the fuel tank(s).  The item no.
is 7539003779.  At $0.19/ea, these could be just the ticket.

Mark S.

Mark

Thanks... sounds like  an affordable price:).

One forseeable problem is the IC chips need power right? Probably
about 3 vdc. and 10  miliamps?  Could this cause a spark within the
tank on crash landing or during operation?


Doug in Japan

Doug,
You're concerns are probably well founded, but there are lots of other
 things that could also spark.   I don't see why you couldn't take
some  extra precautions here to make it as safe as can be, like
potting the  whole assembly.  Not sure how long a sense lead it can
handle. I  ordered 10/ea (yeah, I'm a big spender) and will experiment
with them  when they arrive.  Seller claims they will work in
gasoline. We'll see.

Mark
(where did I put my nomex suit)

I doubt if a spark in a closed gasoline fuel tank would cause a problem.
The saturated vapor pressure of gas, at realistic temperatures (outside
of  North and South poles), seems to be too much to make a flammable
mixture. But I would not recommend to install sparkers in fuel tanks.
Jerzy

There is a open cell foam like material used in race car fuel cells that
suppresses fires and explosions.

Paul Lamar

Who drives a car that doesn't have an in-tank electric fuel pump - uses at
least 12V/2A.  Jerzy is correct.


Matt-