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czechsix(at)juno.com
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 Posted: Mon Jun 05, 2006 7:00 pm Post subject: princeton capactive fuel probe |
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Hi Tom,
I bought the capacitive Princeton probes through Grand Rapids to use with
my EIS-4000 and the probes came already bent and ready to install in the
RV
tanks. I have an -8A but as far as I know the same bend profile will
work
in the -6 series too. Might not hurt to double-check before ordering.
As far as using them "successfully" goes, I've had decent results with
mine. You go through a calibration setup procedure where you turn power
on, push a button on the probe with the tank empty for the empty set
point,
then fill the tank and push the button again for the full set point. The
first time I did this it worked fine on one tank but the other tank was
reading 0.0 and the LED on the probe was flashing an error code.
Instructions said to try the calibration procedure again before calling
Princeton. This is a bit of a pain because you have to empty the tank
completely....it worked out ok for me because I was flight testing and
figured what the heck, I should run the tank dry in the air anyway just
to
make sure I can really use all the fuel in flight. After resetting it
the
probe has worked fine.
My only complaint--and it's a minor one--is that with the tanks full, the
reading from the senders varies by about a gallon. You can program the
EIS
to show whatever quantity you want when the sender is at the full
level...I
measured about 11 gals in my tank when the fuel is at the top of the
sender
so that's what I programmed into the EIS. But the actual reading after
refueling is anywhere from 10.0 to 10.9, and it varies from day to day.
I
didn't expect capacitive probes to wander in their readings like this.
Anyway, the important part is that they do seem to read accurately when
near empty. I have an alarm on my EIS set up to warn me when fuel level
is
reading 1.0 gals in either tank. It will start to flash at me a few
minutes before the engine quits. So I'm satisfied with that aspect of
it.
One other note of interest, I originally installed Vans float sensors in
my
tanks but decided to change to capacitive in hopes that I'd never have to
yank them out and change them (time will tell...). I made the swap
before
mounting my wings so it was easy. The curious thing is that in order to
install the Princeton probes, I had to install both the probe and the
tank
access plate at the same time, with a series of twists and turns. If you
install the probe in the access plate first, or install the plate and
then
try to put in the probe, it won't work. I just mention this because it
may
be a lot harder to retrofit a flying airplane than it was with the wings
off....
Hope this helps,
--Mark Navratil
Cedar Rapids, Iowa
RV-8A N2D getting ready for 50 hr oil change..
------------------------------------------------------------
From: sarg314 <sarg314(at)comcast.net>
Subject: princeton capactive fuel probe
I'm looking for a capacitive fuel probe/gauge to use in my old (circa
1999) RV-6A kit (tanks already built). The princeton probes look
interesting because they could probably be used in this tank. You can
specify a bendable section which I think would make it useable with the
standard RV-6A tank configuration.
Has any one used these probes successfully?
--
Tom Sargent, RV-6A
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Tdawson(at)avidyne.com
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| Posted: Mon Jun 05, 2006 8:35 pm Post subject: princeton capactive fuel probe |
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Skysports will create custome-length bendable capacitive probes for about $75-80 each, too. They'll even tweak the electrical output characteristics (within reason) to match whatever gauge/engine system you're using . ..
TDT
RV-10 40025
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Tue Jun 06, 2006 4:11 am Post subject: princeton capactive fuel probe |
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Responding to an AeroElectric-List message previously posted by: Mark E
Navratil <czechsix(at)juno.com>
6/6/2006
Hello Mark, You wrote:
<<...... skip...... My only complaint--and it's a minor one--is that with
the tanks full, the
reading from the senders varies by about a gallon. You can program the
EIS to show whatever quantity you want when the sender is at the full
level...I measured about 11 gals in my tank when the fuel is at the top of
the
sender so that's what I programmed into the EIS. But the actual reading
after
refueling is anywhere from 10.0 to 10.9, and it varies from day to day.
I didn't expect capacitive probes to wander in their readings like this.
Anyway, the important part is that they do seem to read accurately when
near empty.......skip....... --Mark Navratil>>
I am reluctant to dip my toe into any electrical waters, but my
understanding is that the capacitance probes measure the changing
capacitance between the center rod and the outer tube of the probe as the
level of fuel changes inside the tube. Fuel and air have different
capacitive characteristics. Through electrical magic the system displays
this capacitance as fuel quantity.
But also the density of fuel can change with changing temperature and this
changing density can change the capacitance characteristics of the fuel. So
with exactly the same amount of fuel in your tank on two different occasion
you could read different fuel quantity depending upon the temperature
difference between those two occasions.
This could explain the variations in your fuel quantity readings.
OC
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europa(at)triton.net
Guest
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| Posted: Wed Jun 07, 2006 3:52 am Post subject: princeton capactive fuel probe |
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We fitted a Princeton capactive probe in our Europa. We are using premiun
auto gas. What we have learned is that
ethanol changes the dielectric value a lot which results in gross errors
(inaccurate readings). The amount of ethanol added by the gasoline
distributors seems to vary depending on season of the year (we are in
Michigan).
Other Europa owners have noted that aviation gas (100 LL) and auto fuel have
different dielectric values which results in about a 5% error in reading.
What some have done instead of using a capactive probe, is to fit a gage
pressure sensor at the bottom of the tank (or in a line coming from the
bottom) and measure the weight of fuel which is more constant and isn't
affected by the addition of ethanol. See Level Master at www.msiusa.com or
http://catalog.sensing.honeywell.com and look for 26PCAFB6G for examples of
sensors.
Jim & Heather Butcher
Europa XS N241BW
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retasker(at)optonline.net
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| Posted: Wed Jun 07, 2006 6:59 pm Post subject: princeton capactive fuel probe |
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I would highly NOT recommend the MSI part. The pressure fitting is made
of PVC! Not a good thing to expose to gasoline unless you want a large
hole in the bottom of your gas tank (where the sensor was)!
The Honeywell part might work, but the gasoline would definitely affect
some of the internal materials - causing inaccuracies if you are lucky
or failure if you are not.
While the idea is a good one, I would not install either of these parts
on my airplane!
Dick Tasker
Jim Butcher wrote:
<snip>
| Quote: | Other Europa owners have noted that aviation gas (100 LL) and auto fuel have
different dielectric values which results in about a 5% error in reading.
What some have done instead of using a capactive probe, is to fit a gage
pressure sensor at the bottom of the tank (or in a line coming from the
bottom) and measure the weight of fuel which is more constant and isn't
affected by the addition of ethanol. See Level Master at www.msiusa.com or
http://catalog.sensing.honeywell.com and look for 26PCAFB6G for examples of
sensors.
Jim & Heather Butcher
Europa XS N241BW
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noelloveys(at)yahoo.ca
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| Posted: Wed Jun 07, 2006 7:16 pm Post subject: princeton capactive fuel probe |
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Capacitive fuel gauges also require a "wet probe" This is a small probe
that is at the bottom of your tank and is always covered with fuel. It
actually does tow jobs ... First it allows the fuel gauge to be accurate
when the tanks are close to empty and it will do a good job as a water
detector. A little water on the wet probe will lower the capacitance to a
point where a logic circuit can turn on a "Water in the gas" light.
Most tanks will have more than one probe in them. Most transport cat planes
will have several in each tank so the fuel quantity will be pretty accurate
even when the plane is in a turn, climbing or descending. The probes
themselves are not usually uniform in shape or diameter. These odd shapes
are another way of correcting the gauges for the shape of the fuel tanks.
Sound confusing??? It is a bit.
Noel
[quote] --
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noelloveys(at)yahoo.ca
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| Posted: Thu Jun 08, 2006 3:57 am Post subject: princeton capactive fuel probe |
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Just another reason to fight the booze!
Noel
[quote] --
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europa(at)triton.net
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| Posted: Thu Jun 08, 2006 6:48 am Post subject: princeton capactive fuel probe |
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Dick,
Thanks for your comments. I agree the MSI PVC housing is a problem. I was
thinking about disassembling the sensor and machining a brass housing. The
nice thing about the MSI is that it already has an amplifier so the output
voltage can go directly into my BMA EFIS.
I think the materials in the Honeywell are OK for gasoline. I know several
Europa drivers who have had this installed for over two years with no
problems.
I'm still trying to decide which way to go.
Jim Butcher
Europa XS N241BW
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