fuel level cal?

[13brv3]

Greetings,

I'm going to have to do the cal on the fuel levels for my RV-8, and have a couple questions.

1- What amount (or amounts) of fuel will it ask me to pour for each step? If this is dependent on the size of the tank, they are 21 gallons each. I just want to make sure I have a proper size container to pour in the required amount.

2- Is there any way to copy the results from one tank to the other? The tanks, senders, floats were set up as close to the same as I can get them, so any error would be pretty small, and it would save the hassle of doing this twice.

3- On an RV fuel tank, there will be a little space for fuel below the lowest point of the level sender float, and a decent amount of fuel lever above the float level. For the sake of discussion, we'll say the float will start to move up when you hit 1 gallon, and stop moving up when you reach 16 gallons. What will the Dynon show for level from 0-1 gallons, and from 16-21 gallons?

Thanks,
Rusty

PS- sorry for all the questions, but the time to fly is near

 

[dynonsupport]

1) For this size tank, it will be 2 gallon increments.

2) Unfortunately not. Each tank will still need to be calibrated individually. Even given this theoretical symmetry, the resistance values can vary a bit from sender to sender and tank to tank.

3) The low side generally isn't a factor since most people position their senders to bottom out at the lowest portion of their tanks. However, if there was some space under the sender, the EMS would simply read 0 until the sender starts to move. So as the tank empties, then, at some point, the fuel quantity would drop off off to 0 once the sender bottoms out. There may actually be a gallon of fuel left in the tank beyond that, but there is no way for us to measure it if the sender can't measure it. Similarly (and more commonly), if your sender tops out before you are done filling, say at 16 gallons as you propose, the EMS would read 16+ for that tank when it is fuller than 16 gallons. Again, we can't measure what we can't sense, but we can let you know that there are at least 16 gallons in the tank.

 

[dynonsupport]

Just to enhance the above description, the EMS always shows you that you have "at least" X amount of gallons in the tank, so it transitions to 15 gallons the instant it sees less than 16.0 gallons on board. Because of this, if your sender bottomed out at 3 gallons, the unit would read 5, 4, 3, 0 and would read 0 from 2.9 gallons all the way until truly empty.

 

[13brv3]

Thanks for the great answer! Bummer about having to do this twice, but in the long run, it will make for a better calibration.

I only put about 4 gallons in each side for the initial engine runs, and didn't see any reading at all for fuel. I'm pretty sure that would be enough to move the floats, even in the taildragger stance. Will the fuel just read zero until you do a cal?

Thanks,
Rusty

 

[dynonsupport]

The EMS will not show any fuel until it's calibrated. It should say "CAL" instead of a fuel level.

 

[13brv3]

Thanks for the confirmation. It's pretty hard to screw up the wiring for a fuel level sender, but I was starting to wonder :

Cheers,
Rusty

 

[13brv3]

Greetings,

After huffing more than my annual requirement of Avgas fumes, I now have calibrated fuel level gauges

One tip for anyone who hasn't done this yet- don't try to do it on the internal battery unless you're quicker than I am. I was at about 16 gallons when my battery died, and I had to drain all the fuel back out, and start over

Now that I wrote down the numbers that are read from the sensors during the cal, I could easily re-create these values with a variable resistor if I ever needed to go through this again. With proper backups of the settings, that shouldn't be necessary though.

Unfortunately, due to several factors, one tank shows a max of 16 gallons, and the other shows a max of 14. This is annoying, but I can live with it for now. I may eventually "tweak" the numbers to make them both show the same amount. I'll try to resist though

Cheers,
Rusty