Nigel Graham wrote:
>
> You could fit LED/photo-detectors across the sight tube to detect the fuel
> level at set points like Full, 1/2 Full and the Reserve threshold.
> Slave these to small bright LEDs on the instrument panel and you'll still be
> able know your fuel contents when your spine becomes non-flexible and you
> become geriatric ......though by that time you probably won't remember why
> they are flashing!
>
> Nigel (the other one)
Not a bad idea, but some electronic circuits unfortunately end up
needing the Rube Goldberg touch. Even infrared detectors are
sensitive a bit to visible light and the sun's heating effect, and
change in detector output, fuel vs. no fuel, will probably be less
than such effects. So the sight tube would be best enclosed so as to
be dark using even infrareds. You still have problems of temp and
voltage stability when measuring tiny voltage changes - plus change in
color of the tubing over time, so a tip from the many books on sensor
circuit theory is to reference each LED/detector pair output to one
located above the full level. And each level-reading LED/detector
pair will require trimmers to adjust voltage, because we're now
sensing hair-trigger differential voltage, but relieved of the many
design problems of sensing absolute voltage. I like the idea, but
unfortunately requires some more circuitry!
Best,
Fred F., N3EU
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