Q for Jim Weir or others: solid state fuel level probes?

Jim or anyone else who has 'been there',

Are circuit boards available for the capacitive fuel guages featured in
the year2000 Kitplanes articles?

Or (more desirable to me) is there an easily fabricated optical sensor
available for fuel level measurement?

Other options???

Thanks,

Charlie

Charlie England
shared these priceless pearls of wisdom:

-Jim or anyone else who has 'been there',
-
-Are circuit boards available for the capacitive fuel guages featured in
-the year2000 Kitplanes articles?

Unfortunately, no. For a couple of good reasons. One that I know you
understand is liability. While I have no good reason to believe that the design
is anything but triple-redundant safe, the Denver case outlines that anybody
whose name is anywhere on the airplane will get to explain to a particularly
picky black robe why their part of the airplane could not have possibly been
involved in the accident.

Two is that I get about one request every six months for a circuit board. That
makes it economically unfeasable to even do the layout, much less make a hundred
boards and have a 50 year supply sitting on the shelf.


-
-Or (more desirable to me) is there an easily fabricated optical sensor
-available for fuel level measurement?

Optical? Hmmm...with green fuel, blue fuel, red fuel, and clear fuel around
(and we all know there's no fuel like an old fuel) I'm not sure what sort of
optical system would be stable and sensitive enough to cover this range of
optical barriers.


-
-Other options???


I've been particularly intrigued with the possiblity of using the Polaroid
autofocus sonar setup but have never investigated it. THAT is damn near totally
failsafe.

Jim

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Jim Weir wrote:
Charlie England
shared these priceless pearls of wisdom:

-Jim or anyone else who has 'been there',
-
-Are circuit boards available for the capacitive fuel guages featured in
-the year2000 Kitplanes articles?

Unfortunately, no. For a couple of good reasons. One that I know you
understand is liability. While I have no good reason to believe that the design
is anything but triple-redundant safe, the Denver case outlines that anybody
whose name is anywhere on the airplane will get to explain to a particularly
picky black robe why their part of the airplane could not have possibly been
involved in the accident.

Two is that I get about one request every six months for a circuit board. That
makes it economically unfeasable to even do the layout, much less make a hundred
boards and have a 50 year supply sitting on the shelf.


-
-Or (more desirable to me) is there an easily fabricated optical sensor
-available for fuel level measurement?

Optical? Hmmm...with green fuel, blue fuel, red fuel, and clear fuel around
(and we all know there's no fuel like an old fuel) I'm not sure what sort of
optical system would be stable and sensitive enough to cover this range of
optical barriers.


-
-Other options???


I've been particularly intrigued with the possiblity of using the Polaroid
autofocus sonar setup but have never investigated it. THAT is damn near totally
failsafe.

Jim

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com
There are currently available liquid level sensors that use a light
source feeding a plexiglas rod with the sensor (IIRC) adjacent to the
light source. Change in refraction between covered/uncovered end of the
rod causes a 0/1 change in output state of the sensor. These are
typically promoted as low-level sensors. I am hoping for a variation on
this sensing technique. I've seen proposals for multiple rods/sensors,
but no 'cookbook' & parts source to build one 'cheap'.

Charlie

"Jim Weir" wrote in message
...

Optical? Hmmm...with green fuel, blue fuel, red fuel, and clear fuel
around
(and we all know there's no fuel like an old fuel) I'm not sure what sort
of
optical system would be stable and sensitive enough to cover this range of
optical barriers.


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Well, there's brute force. Just install a closed circuit TV camera that
looks in through a window in the tank. Nothing like directly eyeballing how
much fuel there is in the tank. Make sure there is a "dipstick" in the
camera view. Hey, everybody's going "glass cockpit" anyway.

The fiber optic trick.... Just use a bundle of plastic fibers, each cut to
a different length on the tank end. In the cockpit, just break out the
bundle into a vertical array of fiber ends. Illuminate the interior of the
tank with "ultrabright" LED's. A fiber end in the cockpit will either
illuminate if the other end is submerged in fuel or go dark if it isn't.
Want a brighter display? Just install more LED's.

Bill Daniels

I believe I saw a posting a year or more ago that that will work with out
the light. If I remember correctly the light from the cockpit will be
reflected when there is no fuel and will be dark when there is..I thought
about using this on an ultralight gas tank. Buy a standard 5 gallon gas can.
install a fuel pick up in the lid and the fuel gauge sensor in the vent.
When I need gas I can unsnap the the bungee cords, pull the cap and vent and
take the whole thing down to the gas station and fill it up, and the FAA
want be able to claim my tank is too big.

Cheers
Jeff
"Bill Daniels" wrote in message
...

"Jim Weir" wrote in message
...

Optical? Hmmm...with green fuel, blue fuel, red fuel, and clear fuel
around
(and we all know there's no fuel like an old fuel) I'm not sure what
sort
of
optical system would be stable and sensitive enough to cover this range
of
optical barriers.


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Well, there's brute force. Just install a closed circuit TV camera that
looks in through a window in the tank. Nothing like directly eyeballing
how
much fuel there is in the tank. Make sure there is a "dipstick" in the
camera view. Hey, everybody's going "glass cockpit" anyway.

The fiber optic trick.... Just use a bundle of plastic fibers, each cut
to
a different length on the tank end. In the cockpit, just break out the
bundle into a vertical array of fiber ends. Illuminate the interior of
the
tank with "ultrabright" LED's. A fiber end in the cockpit will either
illuminate if the other end is submerged in fuel or go dark if it isn't.
Want a brighter display? Just install more LED's.

Bill Daniels

"Jim Weir" wrote in message
...
Charlie England
shared these priceless pearls of wisdom:

-
-Or (more desirable to me) is there an easily fabricated optical sensor
-available for fuel level measurement?

Optical? Hmmm...with green fuel, blue fuel, red fuel, and clear fuel
around
(and we all know there's no fuel like an old fuel) I'm not sure what sort
of
optical system would be stable and sensitive enough to cover this range of
optical barriers.


-
-Other options???


I've been particularly intrigued with the possiblity of using the Polaroid
autofocus sonar setup but have never investigated it. THAT is damn near
totally
failsafe.

Jim

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

If you want to do some tinkering of your own (legal disclaimer here..) you
may want to look at sensor chips from QProx (www.qprox.com). They have a
couple of capacitive level monitor chips like the QT300/301 or QT117L that
may provide real-time non-contact level information. If you have a non-metal
tank you may be able to just attach two strips on the side of the tank and
be done.

Jim, what do you think?

Rob

I think the chips themselves are worth investigating. I do have a prejudice
against UK semiconductor manufacturers, having had a major one and a minor one
simply stop producing parts that rendered several tens of thousands of dollars
of hardware and engineering time down the drain.

I realize that they are not ALL like that, but the only two that have screwed me
thus far in 40 years have been UK based.

Jim


-If you want to do some tinkering of your own (legal disclaimer here..) you
-may want to look at sensor chips from QProx (www.qprox.com). They have a
-couple of capacitive level monitor chips like the QT300/301 or QT117L that
-may provide real-time non-contact level information. If you have a non-metal
-tank you may be able to just attach two strips on the side of the tank and
-be done.
-
-Jim, what do you think?
-
-Rob
-

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

Jim Weir wrote:

I think the chips themselves are worth investigating. I do have a prejudice
against UK semiconductor manufacturers, having had a major one and a minor one
simply stop producing parts that rendered several tens of thousands of dollars
of hardware and engineering time down the drain.

I realize that they are not ALL like that, but the only two that have screwed me
thus far in 40 years have been UK based.

Jim

-If you want to do some tinkering of your own (legal disclaimer here..) you
-may want to look at sensor chips from QProx (www.qprox.com). They have a
-couple of capacitive level monitor chips like the QT300/301 or QT117L that
-may provide real-time non-contact level information. If you have a non-metal
-tank you may be able to just attach two strips on the side of the tank and
-be done.
-
-Jim, what do you think?
-
-Rob
-

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

I've used the QT114 for a single point fluid (alcohol) level control in
a one liter plactic cylinder. Precise within fractions of a mm. I also
used the QT110 for an isolated (behind a glass display window) proximity
switch for one of our students' Physics class projects. The QT117 or
QT300 might work for a tank level gauge. They even have "slosh" filter
software built in,

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Isn't this just a capacitance meter on a chip?

Evan
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"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