Andrew Sarangan wrote in
:

The reason for the weight sensor was because he did not want to
penetrate the fuel tank to add his sensors. Once inside the fuel tank,
I do not see the benefit of an optical sensor vs a float sensor. In
fact, I don't quite understand why float sensors are so inaccurate in
the first place. It is just a variable resistor. The shape of the fuel
tank can be easily calibrated out. Averaging the sloshing is equally
easy to do. Anyone know what makes them so notoriously inaccurate?


The mechanical ones, like the wire in a cub or T-craft, was very reliable.
The mechanicla dial gauges you see in the Luscombe, Citabria and some older
Cessnas are also pretty good, though you have to undertand what the
airplane's attitude can do to some indications. It's when there is an
electrical connection that it seems to go wrong.

There is one system I have seen in an old car that was extremely accurate
and reliable. It had a tube that ran from the panel to the fuel tank and
inside th etank it branched out to a a number of tubes, about eight, I
think. Each tube had a little pan shaped dish on it. In the panel there was
a small liquid barometer type device theat sensd the pressure from the
tank. The liquid in the gauge was a red substance, supposedly metal, that
showed the level in eights of a tank. I can't remember what the stuff was
but it was extremely dangerous to handle and you had to send the gauge to a
specialist to have it filled.
It worked really well, bu tI doubt it would be much use in an airplane.


Bertie