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Bob Turner
Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA
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 Posted: Sun Dec 19, 2010 9:49 pm Post subject: fuel sender info into GRT EIS |
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I am starting a new post because I think this topic deserves one on its own. It was started at the end of the "infinity grips" post. The question was how to interface (I presume standard fuel float gauges) fuel levels into the GRT EIS?
I haven't done it yet, but my plan is to bias the senders with 12 volts thru a 1,000 ohm resistor.This should give about 0.4 volts when full, and about 2.4 volts when empty. The EIS then needs to be programmed with a "-" to invert the sensing (low is full, high voltage is empty), and the appropriate offsets and scale factors have to be entered. With this simple system the readout will not be linear. If you want that you'll have to feed the probes with a constant current source.
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Bob Turner
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carl.froehlich(at)verizon
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| Posted: Mon Dec 20, 2010 5:41 pm Post subject: fuel sender info into GRT EIS |
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Bob,
Recommend you follow the GRT EIS installation instructions and use the 4.8V excitation (pin #1) from the EIS. I used a 330 ohm resistor between pin #1 and the sender, the other side of the sender connected to ground via a ground wire under a screw head on the sender case. The EIS manual has a diagram of this wiring.
Here is a cut and paste from a post I did on the RV-8 list on how to calibrate the EIS so that the fuel level reads out in gallons.
I used the standard float senders in my 8A, reading out the tank level on a Grand Rapids EIS. The EIS reads out in gallons. I calibrated the EIS readout by adding one gallon at a time to the tanks, taking data at each point on what the EIS was seeing. Using the old high school algebra equation Y = mx +b, you set the slope of the curve (m) and the offset (b) into the EIS so that the sender input to the EIS (x) reads out in gallons left in the tank (Y). Using the EIS nomenclature, m is 1SF and b is 1OFF (for the AUX 1 input as example). So the equation is Gallons = (1SF)(x) + 1OFF
If you start with some round numbers (say 1SF = 1 and 1OFF = 0), make a graph where y is the number of gallons you have put into the tank, and X is the EIS reading (since 1SF=1 and 1OFF = 0, then the readout is x. Construct a straight line through the points, determine the slope,1SF and 1OFF such that the readout, Y, equals actual gallons in the tank. Note the instructions from the EIS manual on setting forward/reversing sensing (+/-) and 1OFF “Negative values are entered into the corresponding 1Off, 2 Off, 3OFF or 4OFF entry at twice their magnitude -1. Positive entries are entered as twice their value. Thus if the desired offset is -5, a value of 9 is entered. Similarly, if the desired offset is +8, 16 is entered”.
The senders in my 8A do not indicate more than 16 gallons as that is the full “up” range of the float. From 0 – 16 gallons however the reading is within a gallon or so. I find the comparison between the fuel level readings and the fuel flow meter to be more than adequate as indication of a problem. On one flight I was reading 5 gallons less on the tank levels than the fuel flow meter said I had. I elected to do a fuel stop just to make sure. The tanks were 5 gallons down from the fuel flow indication. The cause of the problem was a line guy not filling the tanks up all the way. This was the first, and last time I let someone else fill up the tanks.
No fuel tank indication will ever be as accurate as a properly working fuel flow meter - but no fuel flow meter knows what is really in the tank, only what you took out of it. Both are needed.
I have the left tank on the AUX 1 input, the right tank on AUX 2. Typical Vsf is 25 and Voff is 59. Your values will of course be different.
Carl
RV-10 (cowl and plenum finishing)
RV-8A (600 hrs)
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bruce1hwjohnson(at)yahoo.
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| Posted: Mon Dec 20, 2010 6:22 pm Post subject: fuel sender info into GRT EIS |
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Thanks allot Carl, I read your email and went out and re-read the instructions and figured it out. I got 24 and 25 gallons on the read out. Thanks again and I will call in the Am to thank you personally.
From: Carl Froehlich <carl.froehlich(at)verizon.net>
To: rv10-list(at)matronics.com
Sent: Mon, December 20, 2010 5:27:32 PM
Subject: RE: fuel sender info into GRT EIS
Bob,
Recommend you follow the GRT EIS installation instructions and use the 4.8V excitation (pin #1) from the EIS. I used a 330 ohm resistor between pin #1 and the sender, the other side of the sender connected to ground via a ground wire under a screw head on the sender case. The EIS manual has a diagram of this wiring.
Here is a cut and paste from a post I did on the RV-8 list on how to calibrate the EIS so that the fuel level reads out in gallons.
I used the standard float senders in my 8A, reading out the tank level on a Grand Rapids EIS. The EIS reads out in gallons. I calibrated the EIS readout by adding one gallon at a time to the tanks, taking data at each point on what the EIS was seeing. Using the old high school algebra equation Y = mx +b, you set the slope of the curve (m) and the offset (b) into the EIS so that the sender input to the EIS (x) reads out in gallons left in the tank (Y). Using the EIS nomenclature, m is 1SF and b is 1OFF (for the AUX 1 input as example). So the equation is Gallons = (1SF)(x) + 1OFF
If you start with some round numbers (say 1SF = 1 and 1OFF = 0), make a graph where y is the number of gallons you have put into the tank, and X is the EIS reading (since 1SF=1 and 1OFF = 0, then the readout is x. Construct a straight line through the points, determine the slope,1SF and 1OFF such that the readout, Y, equals actual gallons in the tank. Note the instructions from the EIS manual on setting forward/reversing sensing (+/-) and 1OFF “Negative values are entered into the corresponding 1Off, 2 Off, 3OFF or 4OFF entry at twice their magnitude -1. Positive entries are entered as twice their value. Thus if the desired offset is -5, a value of 9 is entered. Similarly, if the desired offset is +8, 16 is entered”.
The senders in my 8A do not indicate more than 16 gallons as that is the full “up” range of the float. From 0 – 16 gallons however the reading is within a gallon or so. I find the comparison between the fuel level readings and the fuel flow meter to be more than adequate as indication of a problem. On one flight I was reading 5 gallons less on the tank levels than the fuel flow meter said I had. I elected to do a fuel stop just to make sure. The tanks were 5 gallons down from the fuel flow indication. The cause of the problem was a line guy not filling the tanks up all the way. This was the first, and last time I let someone else fill up the tanks.
No fuel tank indication will ever be as accurate as a properly working fuel flow meter - but no fuel flow meter knows what is really in the tank, only what you took out of it. Both are needed.
I have the left tank on the AUX 1 input, the right tank on AUX 2. Typical Vsf is 25 and Voff is 59. Your values will of course be different.
Carl
RV-10 (cowl and plenum finishing)
RV-8A (600 hrs)
--
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Bob Turner
Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA
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| Posted: Mon Dec 20, 2010 6:59 pm Post subject: Re: fuel sender info into GRT EIS |
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Carl, Thanks for the info. I will go look again, but I couldn't find any info on interfacing fuel float senders to the GRT EIS. The "manual" is just a bunch of papers stapled together, but as I said I couldn't find any reference to fuel float gauges. That's why I just guessed at using buss voltage (13.6) and a 1K resistor. I'm aware that if the alternator goes off line, the readings will then be off.
Bob
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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Bob Turner
RV-10 QB |
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jesse(at)saintaviation.co
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| Posted: Tue Dec 21, 2010 7:14 am Post subject: fuel sender info into GRT EIS |
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The plane I have to calibrate was originally installed with a Capacitance fuel level sender and has been retrofitted to the resistive float system. The plane has the EIS 4000 engine monitor. Does anybody know the difference in how they wire up? The owner says the tanks only read accurately from 5-6 gallons left in each. Any ideas? Just need to recalibrate with the normal procedure?
Thanks
do not archive
Jesse Saint
Saint Aviation, Inc.
jesse(at)saintaviation.com
C: 352-427-0285
F: 815-377-3694
On Dec 20, 2010, at 9:59 PM, Bob Turner wrote:
| Quote: |
Carl, Thanks for the info. I will go look again, but I couldn't find any info on interfacing fuel float senders to the GRT EIS. The "manual" is just a bunch of papers stapled together, but as I said I couldn't find any reference to fuel float gauges. That's why I just guessed at using buss voltage (13.6) and a 1K resistor. I'm aware that if the alternator goes off line, the readings will then be off.
Bob
--------
Bob Turner
RV-10 QB
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=323979#323979
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Tim Olson
Joined: 25 Jan 2007
Posts: 2879
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| Posted: Tue Dec 21, 2010 7:30 am Post subject: fuel sender info into GRT EIS |
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I have the chelton, and the GRT EIS. I hooked mine up using
the 4.8v excite power exactly as the GRT info showed. It works
fine, and actually is reasonably accurate if you calibrate it,
until you get fuller than something in the low-mid 20's of
gallons...when the floats hit the top.
You can also correct for the non-linearity on the Chelton side
a bit.
Tim Olson - RV-10 N104CD
do not archive
On 12/19/2010 11:49 PM, Bob Turner wrote:
| Quote: |
Turner"<bobturner(at)alum.rpi.edu>
I am starting a new post because I think this topic deserves one on
its own. It was started at the end of the "infinity grips" post. The
question was how to interface (I presume standard fuel float gauges)
fuel levels into the GRT EIS?
I haven't done it yet, but my plan is to bias the senders with 12
volts thru a 1,000 ohm resistor.This should give about 0.4 volts when
full, and about 2.4 volts when empty. The EIS then needs to be
programmed with a "-" to invert the sensing (low is full, high
voltage is empty), and the appropriate offsets and scale factors have
to be entered. With this simple system the readout will not be
linear. If you want that you'll have to feed the probes with a
constant current source.
-------- Bob Turner RV-10 QB
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=323880#323880
|
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
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Lenny Iszak
Joined: 23 Mar 2008
Posts: 270
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| Posted: Tue Dec 21, 2010 8:15 am Post subject: Re: fuel sender info into GRT EIS |
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Jesse,
You can quickly get the scale factor and offset if you plug in your number pairs on http://www.wolframalpha.com
Here's an example:
http://www.wolframalpha.com/input/?i=linear+fit+%7B1.3%2C+2.2%7D%2C%7B2.1%2C+5.8%7D%2C%7B3.7%2C+10.2%7D%2C%7B4.2%2C+11.8%7D
or use this type of query:
linear fit {1.3, 2.2},{2.1, 5.8},{3.7, 10.2},{4.2, 11.8}
It will show you the best transfer function and also show you the error at each point. A lot easier and more accurate then doing it by hand.
Lenny
| jesse(at)saintaviation.co wrote: | The plane I have to calibrate was originally installed with a Capacitance fuel level sender and has been retrofitted to the resistive float system. The plane has the EIS 4000 engine monitor. Does anybody know the difference in how they wire up? The owner says the tanks only read accurately from 5-6 gallons left in each. Any ideas? Just need to recalibrate with the normal procedure?
Thanks
do not archive
Jesse Saint
Saint Aviation, Inc.
jesse(at)saintaviation.com
C: 352-427-0285
F: 815-377-3694
On Dec 20, 2010, at 9:59 PM, Bob Turner wrote:
| Quote: |
Carl, Thanks for the info. I will go look again, but I couldn't find any info on interfacing fuel float senders to the GRT EIS. The "manual" is just a bunch of papers stapled together, but as I said I couldn't find any reference to fuel float gauges. That's why I just guessed at using buss voltage (13.6) and a 1K resistor. I'm aware that if the alternator goes off line, the readings will then be off.
Bob
--------
Bob Turner
RV-10 QB
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=323979#323979
|
|
| | - The Matronics RV10-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV10-List |
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