fuel level calibration w/ EIS4000

What I did...

I started by draining the tanks completely, then having the fuel truck add a gallon at a time, with me recording the values off the EIS at each point. I then dove into the calibration sheet from GRT, and came up with the appropriate numbers. After doing the required math, I entered the appropriate scale factors and bias...and the resulting fuel quantities made no sense whatsoever...

I then posted here on the Forum, asking if anyone had some good numbers to start with. Since the SW fuel senders are pretty much repeatable, I used the numbers someone else had worked out, and have never bothered to go back and do any refinement.

The bottom line for me is that my fuel flow is right on accurate, and therefore my totalizer is dead on, and the fuel gages only give me a general idea if there is something in the tank or not. (And sorry, I don't have the numbers handy...)

So for me, the best way to do it was steal someone else's work....mayb that's considered cheating...

Paul

I did less, but similar to Paul

I had one empty tank and one with max (max gauge) fuel. I used the empty tank's reading for both and the full for both. I discovered on my -7A that it will only read up to 16 gallons. The last 5 are not directly readable. This is with float senders. I don't know if the capacitance ones can do any better. The issue is dihedral, of course. Once you have a "full" tank and an empty one, you have all the data you need to work your way through the IRS-like form GRT gives you. It resulted in my case in accuracy to the nearest gallon. I also did some measured drains and calibrated a clear dip tube. Blue permanent marker seems to stay in the plastic when dunked in gasoline. I discovered that the position of the dip tube needs to be consistent so I settled on the aftmost point on the arc of the fuel filler hole.
I hope this is helpful. The hardest part was the GRT form!

Today I began experimenting with the totalizer to see if it will agree with the levels reported. So far, yes it does. Fine adjustment may be necessary, but I try not to fly in situations where a gallon difference is important.

I have the sw senders from vans. the EIS settings I use (After much draining and refilling) are:

AuxSF = 358
AuxOff = 1117

Hope this gets you in the ball park

Doug'

Ours are setup to read zero (and the engine quits) AND 7 gallons ... above seven gallons they just read 7 ... this was the best we could get ... the sender just ended up under fuel when filled above 7 gallons.

See Post Fuel Level Float Type Senders Question

Scott,
Once you understand what you need to do it is quite straight forward.

The system initially indicates the float level in some arbitrary digits; probably millivolts I suppose.
Whatever they are, you need to ADJUST the indications such that the FULL reading indicates 16 Gal more than the EMPTY reading. (The float will hit the top of the tank at around 16 gals.)
This Adjustment is called the AUX SF (Scale Factor).
You then need to subtract the empty reading from BOTH readings so that they read 0 and 16 gallons respectively. This is called the AUX OFF (Offset).
So what you need is the raw readings for tank at empty and at full.

You start the procedure by setting the AUX SF Scale Factor to 100 (effectively100%) and the AUX OFF to zero and recording the raw readings from the tank at EMPTY and at FULL.
You will get numbers displayed like 199 empty and 256 full respectively.

The difference here (256-199) is 57 units, between the empty reading and the full reading, but you want the indicated difference between empty and full to read around 16 gal.
So you need to factor the raw readings of 199 and 256 by 16/57.
Now the readings will be 199 x 16/57= 55 and 256 by 16/57 =71
So now you have readings that are correctly scaled as 71-55=16gals from full to empty and the AUX SF (Scale Factor) has thus been calculated as 16/57 =0.28. Which is then multiplied by 100= 28 (converts it to a %)

Now we have Empty and Full readings of 55 and 71 respectively, so if with subtract 55 from both we have readings of 0 and 16 respectively. So the AUX OFF (Offset) is effectively 55, BUT it needs to be fiddled a bit with the Scale Factor and some other clever stuff that I don?t understand, as it must be an Odd number. But in essence, there you have it.
Scale it and then apply an Offset.

The exact GRT procedure is copied on my previous post titled:
"Fuel Level Float Type Senders Question".
At http://www.vansairforce.com/community/showthread.php?t=10065

Pete.

To drain a tank..

I recommend unscrewing the fuel drain with a funnel underneath, using 5-gallon or whatever gas tanks. Siphon won't work; it will leave at least 5 gallons at the inbd. end. I would not try to pump it out.

Calibration Logic Diagram

Maybe these will help.
Pete.
[/IMG]http://img99.imageshack.us/img99/7307/grtfuelcalibrationlogicoa7.jpg http://img167.imageshack.us/img167/9508/grtfuellevelsenderinfoch2.jpg

Try again