On Sun, 24 Feb 2008 12:50:38 -0800, "RST Engineering"
wrote in
:

I wonder if a pressure sensor placed inside the bottom of the tank could be
made sensitive enough to "weigh" a column of fuel inside the tank above the
sensor.

It should be pretty easy to test by connecting the pressure sensor to
the tank drain. I don't see why such a system would be any worse than
a float-based system.

That would only work for regular sized tanks (no triangles)

I don't know what makes you say that. The pressure sensing system
just needs to be calibrated like one would do with a dip stick, or am
I overlooking something?

but could be integrated over a long enough time to take care of any slosh.

Just a random thought, mindya...and I haven't run the numbers.

Another thought is a string of LEDs separated from photosensors with, say,
10 or 15 of them inside the tank mounted vertically.

Placing electrical conductors within fuel tanks always makes me
nervous. I know Boeing does it, but there have been problems.

Hmmm...any other thoughts for liquid level measurements? Sonar a la
Polaroid?


I'll bet you can get some ideas he
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Breakout board for the Analog Devices 7746 capacitance sensor.

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This is a simple breakout board for the SHT15 humidity sensor from
Sensirion. The SHT15 digital humidity and temperature sensor is
fully calibrated and offers high precision and excellent long-term
stability at low cost.

http://www.sparkfun.com/commerce/pro...oducts_id=8161
The SCP1000 is the very first absolute pressure sensor on the
market to use MEMs technology to grant 17-bit resolution. Under
ideal conditions, this sensor can detect the pressure difference
within a 9cm column of air.

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Ultrasonic Range Finder - Maxbotix LV-EZ0

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An accurate fuel gauge is long overdue in aviation. It doesn't have to
be fancy gadgetry, fuel flow integrators or capacitive sensors. One of
the experimental guys had installed a simple pressure sensor under the
fuel tank which measured the total weight of the fuel tank. While not
perfect, it was far better than anything else I have seen, including
sight gauges.