Tank calibration

Can somebody mail me their calibration readings of the tank.
One can scroll throug all the steps in edit.
I found unusual non liniarities and end up with Skyview telling me the max is 16 gallons whilst i poor 20 in.
The readings are liniair up to 13 gallons and triple in voltage steps for the last few gallons.
I checked the sensor over its full range before closing the tank and it was fine and liniair.

Very annoying is that during calibration the window does not scoll after line 8 so you cannot see whats being stored..in edit you can scoll but not during the calibration process.

Thanks

See this thread for some posts and my numbers are below:
http://www.vansairforce.com/community/showthread.php?p=643487
Fuel calibration went very well. Now, the Skyview "wakes up" thinking that there are two tanks installed, both uncalibrated. So - which do you calibrate? The manual doesn't say. And you can only look at one tank sensor at a time during the calibration - you don't want to pick the wrong one, put in a couple of gallons, and then have to empty it and start over! (Remember, the mains have to be on 2 inch blocks to do the calibration per the PAP.)

Well, it is the LEFT tank to use. I thought they might have chosen the right tank since it is on the right side of the plane. But I went to the calibration page for the right tank and saw that the EMPTY tank reading was at 5 Volts - a nice round and suspect number! So I cancelled out of that and looked at the LEFT tank. It said 2.73 V. Aha!

So I began calibrating the LEFT tank and sure enough as I added the required 2 gallons at a time, the voltage went down. When I was all done I edited off the right tank from the engine display pages. For reference here are my numbers:
Gallons Volts
0 2.73
2 2.46
4 2.26
6 2.06
8 1.83
10 1.58
12 1.31
14 0.74
16 0.66
After adding the 16th gallon, the Skyview said "Last point did not change." I accepted that and completed the calibration. The float pegs out even though the tank and filler neck is not totally full at that point.

More tank

Thanks Bill, thats very helpful.
Funny I found the very same starting voltage of 2.73 and also 0.66 as the full voltage.

So the gauge on the screen says 16+ gal after calibration, but i poured 20 in.
You cannot see the last four gallons. How does that work for you.?
Before closing the tank i checked the resistance and its not pegged anywhere.
It appeared quite liniair with displacements.

between steps i see a variation of about 200 - 270 mV with exception of 12 gal which is about triple that amount.
this is exactly what i found and is way too much variation for non liniarity.

I concluded that the system for some reason skips two steps but Dynon keeps telling me the float pegs which cannot be.
Something strange is going on but i cannot quite work it out.
I would say its a software issue.
Pretty annoying is that the calibration window only shows the first 7 lines and does not scoll down during the procedure.
You can scroll after calibration but then its too late.
I hate draining 20 gallons of fuel.

Hotscam said:

I concluded that the system for some reason skips two steps but Dynon keeps telling me the float pegs which cannot be.
Something strange is going on but i cannot quite work it out.
I would say its a software issue.

Click to expand...

Jack,
Look closely at your fuel tank from the side and visualize where the float is when it is "floated" to the top of the tank.
Now look at the tank behind that point. It slopes upward to a higher elevation than the point where the float is located. Because of this, the sensor does not detect any added fuel that is located in any of the area above the highest level of the float. This is not an issue since it only effects the first 4 gallons that you will burn during a flight (as long as the indicated fuel level begins to drop after 45-60 minutes of flight, you know everything is normal. If it changes to indicate 15 gallons in a shorter time than that, you know that something is wrong (maybe a leak).

As Pilots, we usually care the most about fuel gauges being accurate when we start getting near the lower fuel quantities. On an RV-12, the fuel level indication is actually very accurate from about 15 gallons on down to zero (but normal cross check procedures using time should still always be done to verify).

Jack, after you are satisfied with the calibration I suggest you form a habit of looking at the sight glas before and after each flight, and compare to the dynon level reading as it will build your confidence in the readouts. More importantly it will let you see what is actually in the tank. This tends to make you more aware of fuel burn as well as knowing what is in tank vs. the electronics indication. Most likely do this, but for those who don't it's a good idea.
Dick Seiders

Of course I will keep an eye on actual level, but I keep having the feeling the electronic sensor can do a lot better. So why not try to tackle the problem.
4 gallons is a lot of misreading.
The fuel gauge in car works the same way and is pretty accurate.

Jack,
Car makers have the luxury of making the fuel tanks symmetrically shaped and with a flat bottom. With airplanes it is not always possible.
It is the shape of the tank that causes the top 4 gallons to not be readable. It is not something you can fix unless you want to abandon the float style fuel level sensor and switch to a capacitive sensor system (would require rebuilding the entire fuel tank).

The first 4 gallons on my 6A does not show on the gauge..... not a problem. I always stick my tanks. I will go with a visual for local flights. For X-country, it's always full tanks and fuel stops are by the clock with a lot of reserve.

As far as car gauges, I have had cars that would drop a 1/4 tank in 50 miles, and others that would go over 100 miles on the first 1/4.