nuckolls.bob(at)cox.net Guest
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Posted: Thu Jul 17, 2008 8:38 am Post subject: Fuel level sensors |
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At 10:46 AM 7/17/2008 -0400, you wrote:
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Larry,
Visit Aircraft Spruce and check out product number 10-00399, which is
the AE Fuel Guardian. It consists of two optical fuel level sensors
that work by detecting the change in reflectance of the lens. I
bought some for my aircraft and was concerned that a drop of fuel
still on the lens might produce an incorrect reading. Nope, I played
around dipping them in and out of some water. They respond rapidly
and immediately, no matter how I tried to fool them. Not a cheap
product, but it seems a high quality one. Drill as small hole in your
tank. A threaded nut goes on the inside, trapping rubber washers.
(Note - this is an uncommon metric thread).
Jeff Page
Dream Aircraft Tundra #10
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Optical liquid level sensing is almost an ancient technology.
I first recall encountering this idea in the "Delco Eye" battery
caps of the 1960's that extended a plastic rod from the top of
a battery cap to the cell-filled point on the water-acid
mixture below. A explanation of how this works is offered
in the following patent:
http://www.aeroelectric.com/Reference_Docs/Patents/Optical_Liquid_Level_4670660.pdf
In bright sun, an uncovered tip reflected a high percentage
of ambient light back up to the top causing the center of
the cap to glow green . . . indicating a need for water to
be added.
http://aeroelectric.com/Pictures/Batteries/Delco_Eye_R69_69.jpg
Years later, I crafted an array of 12 lamps and photocells into
a stack of 1/2" thick liquid level sensors that we installed
at the fuel strainer location on a Baron to explore the dynamics
of fuel slosh and outlet un-porting. A column of 12 lamps
on the panel gave instantaneous measurement of fuel level
at the outlet in 1/2" increments. Had the privilege and
pleasure of meeting and flying with Al White on that program!
http://en.wikipedia.org/wiki/Alvin_S._White
Some years later, I participated in a program that developed
a wide range of optical sensors for the local aircraft
industry. See:
http://www.electromech.com/liquidlevel3RED.html#
In years since, this technology has exploded into a
constellation of products. Generally speaking, the
technology has worked well on airplanes in jet A,
100LL, mogas, hydraulic oil, de-ice fluid, water
tanks, etc.
I can think of only one more user friendly way
to do this . . . and it may become a product. But
in the mean time choices for suitable products
are plentiful.
Bob . . .
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