Fuel Edit Not Working Correctly

[Dynon101]

My fuel tanks were previously calibrated however I wanted to make sure that they were accurate so I did a edit of the fuel system calibration results. I had to do this because the total capacity was unknown prior to filling it up and therefore I had no way of doing the 10 equal pours.

When I entered the EMS Hardware calibration and selected the specific tank, I know that I physically poured in 25 gallons and I can see that the sensor voltage is steady at 2.37 volts. I then push the adjust button and enter line item 5 and adjust the value to 2.37 and that line item already had a value of 25.0 gallons when.

When I hit save and then exit all the way out I look at my screen and it shows 27 gallons. I go back in again and the sensor voltage is still 2.37 volts and the gallon value is still 25.0 gallons however it changes to 27 on the screen when I exit.

How can this happen?

Any suggestions or advice would be greatly appreciated

 

[Dynon]

The calibration system is actually designed to deal with you not knowing your exact capacity up front. Because of individual tank sensor geometry, unmeasurable quantities at the bottom or the top of the tank, virtually no one knows what their measurable fuel quantity is.

When you give the system your quantity at the beginning, you're giving it a ballpark number that it uses to ask you for appropriate pours. The actual quantity measurements then set the actual numerical values. It also lets SkyView cleverly compute when you're topped out, and won't lie to you to show you fuel that it doesn't know is there. For example, if your sensors only move from 0-14 gallons, but you have a 16 gallon tank (this is VERY common), when you're above 14 gallons, you'll only see "14+" on the display.

Anyway, even though you poured in 25 gallons, SkyView may not be able to see all of it. Because of the math that SkyView does to not over-read fuel quantities, playing with some values, particularly ones at the end, can have some undesired effects.

Our advice is to generally not edit the calibration tables manually because it can be confusing to tune them to be truly correct.

For what it's worth, the ideal calibration looks like this: When it asks up front, input what you think your tanks hold. It doesn't need to be perfect: being off a few gallons in either direction doesn't matter. Then, simply follow the on-screen instructions. As you get close to full, you might be asked whether you really added fuel if the sensors stop moving as you get close to physically full. At this point, keep answering yes and keep on going. When you're full, press full. Note that it's not important that you have X identical pours. It's important that you add what it asks you to add. For many small aircraft, it will ask for 1 or gallon pours. Make sure you add that amount in each pour, not some other number that divides out into some round number of even pours.

 

[Dynon101]

>Our advice is to generally not edit the calibration tables manually because it can be confusing to tune them to be truly correct.

Confusing for me or the SV system?

The process seemed really straight forward...pour in 5 gallons a side...wait a few minutes for values to stabilize (because I do not have a way to isolate each tank it takes a few seconds for the fuel levels to balance out)...then enter the the left side sensor, note the voltage value presented at the top of the screen is showing steady (like 1.37 volts) and enter 1.37 volts and 5 gallons and then repeat this step for the right side tank and each additional pour.

What was confusing (and irritating) is that at 15 gallons I entered 15 gallons and then exited out and the screen showed 17 gallons. I went back in and confirmed that the same voltage value was displayed at the top of the screen and that same voltage value and 15 gallons was still entered however when exiting out the tank still showed 17 gallons...

What would cause this?