"Evan Carew" wrote in message
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Isn't this just a capacitance meter on a chip?

Evan

Yes and no. It's not meant to measure absolute capacitor values. It compares
a relatively large fixed capacitance (reference capacitor) to a much smaller
external capacitance. The external capacitance can be two metal strips
attached to the tank, right next to eachother. The air around the strips,
the plastic of the tank and the fuel inside the tank form the dielectricum
for the small capacitor. When flying, the fuel slowly gets replaced by air,
so the capacitor changes value. The chip translates this into digital
information or a PWM signal, depending on which chip you select. PWM is easy
to convert to a voltage, and can drive standard fuel gauges.

The full inner working is a bit more complex and includes

I have used some of their other chips (QT60040) for solid state keypads and
they work quite well. I have ordered a couple QT300's to play with, if it
works out I'll post results here. Possible issues are stability over
temperature, and maybe radio interference. These chips use some kind of
pulse burst system which may introduce noise.

Rob