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Dynon Fuel Calibration

carl nank

Well Known Member
I tried twice to calibrate the fuel level and it continues to show about 3 gallons short in each tank. NOTE: I have the capacitance tanks.

I discussed this with a Dynon rep. at OSH and he claimed to work the system to get the gauge pretty accurate. As you know, the method to calibrate the tanks is to pour 2 gallons in at a time. After you pour each 2 gallons, you activate the button after each pour until you have 21 gallons poured.

The Dynon rep said he starts off by pouring an amount of fuel more or less then the full 2 gallons. I can't remember just exactly what he said. Can someone help me with this?
 
Which fuel sensor / sender are you using? Some capacitance gauges often need to have the sender calibrated first before calibrating the EFIS (to set "full" and "empty", and perhaps some intermediate positions).
 
Cannot get 21 gals on mine

May not be relevant with the capacitance sender but with the float you cannot get to 21 gals on the dynon as the float hits full at around 16 - 18 gals (i.e no change in value as you add the additional 2 gallon increments)
My left tops out at 16 and the right at 18 on the Dynon guages. The Dynon does however register the full 42 when set to full so that the fuel remaining, fuel burned etc from the fuel flow sensor gives an accurate reading (after calibration for position errors etc) of fuel remaining.
Once the fuel level drops below the 16 or 18 gal mark the reading are pretty close to actuals.
Hope this helps
 
Not all capacitance probes can read full tanks either, so it is very important to know what kind you have.
 
OK

I have the Dynon converters (the thingies that are wired to each fuel tank to send the fuel level capacitance amounts to the Dynon) with the capacitance plates, not the floats.

As I said, I discussed the calibration problems with a Dynon rep at OSH. He said he got the individual fuel tank gauges (Dynon) pretty close by fudgeing the amount of fuel at certain steps in the 2 gallon per calibration fill. I think he said he used less then the 2 gallons per toward the beginning of the calabration fill. I am having a tough time getting my head around this process.

I would like to get the gauges closer to accurate especially when I get toward the low fuel area on the gauges. I would like the gauges be pretty accurate especially around 8 gallons left.

The total fuel quantity is right on but the gauges are off when I calibrate the fill at 2 gallon intervals.

Has anybody been able to get it close toward the lower part of the gauges? If so, I would like to find out how you did it.

I appreciate your help.
 
OK

I have the Dynon converters (the thingies that are wired to each fuel tank to send the fuel level capacitance amounts to the Dynon) with the capacitance plates, not the floats.

As I said, I discussed the calibration problems with a Dynon rep at OSH. He said he got the individual fuel tank gauges (Dynon) pretty close by fudgeing the amount of fuel at certain steps in the 2 gallon per calibration fill. I think he said he used less then the 2 gallons per toward the beginning of the calabration fill. I am having a tough time getting my head around this process.

I would like to get the gauges closer to accurate especially when I get toward the low fuel area on the gauges. I would like the gauges be pretty accurate especially around 8 gallons left.

The total fuel quantity is right on, but the gauges are off quite a bit when I calibrate the fill at 2 gallon intervals.

Has anybody been able to get it close toward the lower part of the gauges? If so, I would like to find out how you did it.

I appreciate your help.
 
fuel level

Carl,,,
I have the same set up as you and not been able to get a accurate reading with dynon setup,,, With full tanks, I read 21 gals on each side then as I fly and the level drops, the senders lose accurracy. The gallon reading is about 20% high by half tank. I have to take readings from the fuel flow computer to know what total I have and depend on the gauges only to know that the tanks are balanced..The solution! On advice form an engineer retired from Ball aerospace, (RV6 builder) I have ordered a two sending units (the "thingie" that goes on the fuel tank) from the gentleman working at Grand Rapids. At I least I hope he has not forgotten me as I ordered them when at OSH.... This year.

Dave
 
I followed the direction and have good accuracy on the low end and the high end. The middle span is where the accuracy falls off. There is little change in the capacitance for a wide range of level difference in the middle of the tank capacity. This causes the readings around the middle of the capacity to show a value for a long time and then just drop like a rock when the capacitance finally changes enough to be seen by the Dynon.

This is not a Dynon problem but instead it is an issue with the way Van's capacitive senders are made, installed and the theory behind how they work. There are some things Dynon could do to optimize the converters for use with Van's plates but I doubt they ever will since they made converters that fit more needs than just Van's sender design.

Even with these limitations, Van's capacitive senders are way more accurate than any spam can I have ever rented and that is good enough for me. I use my fuel computer for determining how much fuel I have as it is accurate to within .1 gallons. I use the fuel gauges for a quick cross check on the fuel computer. I use my eyeballs on the tank to save my butt before each flight! After a while, you start to figure out how much fuel you have in a tank just by looking at the fuel level position on the rib and the stiffeners at the bottom of the tank below the fill hole.

Here is my settings and the graph showing what I am describing above:

From ~13g to full mine are very accurate.
From ~4g to empty on the right and 6g to empty on the left mine are very accurate
From ~4 to 14 on the right, you get this stair step indication between levels...
Same thing from ~6 to 12 on the left...

3518j2f.jpg


rjgm8i.jpg
 
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Same with EI gauge

My EI fuel gauges do the same thing on my '9. Just typical of the breed I suppose. They also register high in turbulence (instant fuel) :D:D


I followed the direction and have good accuracy on the low end and the high end. The middle span is where the accuracy falls off. There is little change in the capacitance for a wide range of level difference in the middle of the tank capacity. This causes the readings around the middle of the capacity to show a value for a long time and then just drop like a rock when the capacitance finally changes enough to be seen by the Dynon.

This is not a Dynon problem but instead it is an issue with the way Van's capacitive senders are made, installed and the theory behind how they work. There are some things Dynon could do to optimize the converters for use with Dynon's plates but I doubt they ever will since they made converters that fit more needs than just Van's sender design.

Even with these limitations, Van's capacitive senders are way more accurate than any spam can I have ever rented and that is good enough for me. I use my fuel computer for determining how much fuel I have as it is accurate to within .1 gallons. I use the fuel gauges for a quick cross check on the fuel computer. I use my eyeballs on the tank to save my butt before each flight! After a while, you start to figure out how much fuel you have in a tank just by looking at the fuel level position on the rib and the stiffeners at the bottom of the tank below the fill hole.

Here is my settings and the graph showing what I am describing above:

From ~13g to full mine are very accurate.
From ~4g to empty on the right and 6g to empty on the left mine are very accurate
From ~4 to 14 on the right, you get this stair step indication between levels...
Same thing from ~6 to 12 on the left...

3518j2f.jpg


rjgm8i.jpg
 
Dynon fuel calibration for capacitance tanks

Since nobody answered my question, I guess nobody has the answer. My question was:

The Dynon rep said he starts off by pouring an amount of fuel more or less then the full 2 gallons at a time. I can't remember just exactly what he said. Can someone help me with this?

I appreciate Brantel's chart but the only way to change the numbers in the Dynon is to do another calibration starting with an empty tank and doing the 2 gallon at a time process. I suspect I need to fudge the amount of fuel input at the beginning of the process. I was hoping someone did it successfully and could help me out.

If I can figure it out, I will post my results.
 
May not be relevant with the capacitance sender but with the float you cannot get to 21 gals on the dynon as the float hits full at around 16 - 18 gals (i.e no change in value as you add the additional 2 gallon increments)
My left tops out at 16 and the right at 18 on the Dynon guages. The Dynon does however register the full 42 when set to full so that the fuel remaining, fuel burned etc from the fuel flow sensor gives an accurate reading (after calibration for position errors etc) of fuel remaining.
Once the fuel level drops below the 16 or 18 gal mark the reading are pretty close to actuals.
Hope this helps

Dave, in two or three weeks I hope to have the -9a at the hanger for final assembly. Which means I'm not that for away from calibrating my tanks (Dynon D180 and floats). If I have any trouble getting this done, can I contact you for help?

Thanks

Bob
 
I am not a fan of fudging anything. If you do that then they will always be wrong.

Do you have the values you ended up with at each add?
 
Just calibrated our tanks.

We have the standard Vans floats.

We put 2 gallons in each tank and called that zero. The float had not left the bottom of the tank.

We then proceeded as per the instructions and when we had around 14 gallons in, the value did not decrease any more so we then said yes to adding more until we had reached 22 gallons.

We now have calibrated tanks that are good to go from the float leaving the top of the tank until it reaches the bottom of the tank when there will be 2 gallons left.

It is a compromise but it is a very accurate compromise.

We did a positive check by re draining the fuel and adding a gallon at a time to check - all was very accurate up to 14 gallons and then it remains constant.

Once the float hit the top of the tank, you cannot continue with any more calibration because the sensor is static.

We are happy we have accurate fuel level indications for the lower 2/3rds of the tank.

By the way, we scribed a mark on a dipstick with the tail down at 5 gallons and at 14 gallons. We will leave the aeroplane with 14 gallons a side for planning purposes and add extra for long trips.
 
I followed the direction and have good accuracy on the low end and the high end. The middle span is where the accuracy falls off. There is little change in the capacitance for a wide range of level difference in the middle of the tank capacity. This causes the readings around the middle of the capacity to show a value for a long time and then just drop like a rock when the capacitance finally changes enough to be seen by the Dynon.

This is not a Dynon problem but instead it is an issue with the way Van's capacitive senders are made, installed and the theory behind how they work. There are some things Dynon could do to optimize the converters for use with Van's plates but I doubt they ever will since they made converters that fit more needs than just Van's sender design.

Even with these limitations, Van's capacitive senders are way more accurate than any spam can I have ever rented and that is good enough for me. I use my fuel computer for determining how much fuel I have as it is accurate to within .1 gallons. I use the fuel gauges for a quick cross check on the fuel computer. I use my eyeballs on the tank to save my butt before each flight! After a while, you start to figure out how much fuel you have in a tank just by looking at the fuel level position on the rib and the stiffeners at the bottom of the tank below the fill hole.

Here is my settings and the graph showing what I am describing above:

From ~13g to full mine are very accurate.
From ~4g to empty on the right and 6g to empty on the left mine are very accurate
From ~4 to 14 on the right, you get this stair step indication between levels...
Same thing from ~6 to 12 on the left...

3518j2f.jpg


rjgm8i.jpg

I tried calibrating my tanks today, but quit about 2/3 of the way through because the Skyview kept telling me that the values hadn't changed with each addition of 2 gallons and did I want to use the value it had, etc.?

I was concerned because I was seeing voltage levels (I have Van's capacitive system with the Dynon converters) that started out at empty around .88 or so, but then barely increased, maybe .01-.05 volts, until by the time I got to 16 gallons in a tank, it was somewhere around 1.08 or maybe a little more (don't recall exactly).

What I'm seeing here tells me that this is *okay*, and that I should have just kept going?

I was expecting that the converter would send something relatively low for an empty tank (0.9ish seemed okay) and somewhere near 5.0V for a full tank...is this not correct, and the total voltage range is only in the tenths of a volt?

If that's true, I'll go out tomorrow morning and try again...and be very relieved that I don't have a wiring problem somewhere that I have to track down...

Help?
 
Steve,

Just keep going.

In the end it will work, just not very good.

The design of the Dynon converters is flawed because they over estimated the amount that the capacitance will change empty vs full and they did not give the user the ability to customize the end points of the span.

The results are that they just don't use much of the 0-5v range available resulting in what you are seeing.

I am replacing mine with the Princeton converters that allow the user to calibrate the end points for full use if the range....
 
I am replacing mine with the Princeton converters that allow the user to calibrate the end points for full use if the range....

Hi Brian, would you give me a little more info on these Princeton converts please?? Would really appreciate it.
Thank you,
 
Hi Brian, would you give me a little more info on these Princeton converts please?? Would really appreciate it.
Thank you,

You buy em thru GRT Avionics. They have a few models but for use with an EFIS, I suggest the one with 2 calibration points, empty and full.

You do the calibration on the Princeton unit first. This sets the span to use the full 0-5v range. Then you do a calibration on the EMS per the EMS makers directions and this will make the readings look more linear on the fuel level indicator.

The advantage to using more of the 0-5v range is that the voltage will change more per unit of fuel level change making it easier for the Analog to Digital converter inside the EMS unit to do its thing with the readings.

They are around $95 each and you need 2 of em. They are well made and the electronics box goes inside the cockpit. They come with all you need to install em. The fact that they install inside is another advantage over the Dynon ones. The Dynon ones are prone to getting wet in the wing root and going crazy when they do.

Not sure what else you might want to know. Just let me know...
 
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That's Great!!

That will do nicely Brian. Thank you mucho!!! :D

By way of explanation, and thread related, I have a Dynon FltDk-180 & having the same problems discussed. I have to remove my tanks to improve air vent holes as it takes me forever to fill my tanks presently. Air is not escaping properly. So I'll change out and fix two issues at the same time.

Really appreciate the thread & info.

Cheers,
 
Last edited:
Todd Stehouwer [email protected]

PRINCETON CAPACITIVE FUEL LEVEL PROBES
3133 Madison Ave, Wyoming, MI 49548 (616) 243-8800

148mdz5.png


2w2ncip.png


15arna.png


Keep in mind that the last page of the directions apparently have been copied from the directions that are used with the actual Princeton fuel level probes not Van's senders. Occasionally there are references to the probes that may not make sense with the Vans plates, just use your imagination....
 
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This will not help the OP but may be useful for a subset of the people reading this thread.

I have the Dynon convertors hooked to an EIS 4000. I am happy with them although I have not done the very last step of calibration within the GRT systems.

I used Brantels data to calculate the Y=MX+B values that I needed to go into the EIS. Since you can see Brians data has an inflection point due to the teardrop shape of the leading edge, I chose to curve fit the lower part of the graph so it is accurate at low fuel levels.

The GRT EFIS has a second curve fitting table that will make corrections to EIS data. I plan to use that to make the upper part of the graph fit correctly. The gages read pretty well as they are, so I have not been in a hurry to to this second calibration.
 
Steve and Brantel
Now it is 2018 and I'm trying to calibrate capacitance plates with SkyView HDX and I'm getting that same error you two mention about "voltage didn't change, select YES to continue anyway." So after 10 gallons I quit. But I could see on the screen that voltage was changing about 3/10ths Volt with every 2 gallons.

Should I go back and do it anyway? Or get new capacitance to voltage converters? I'm using the Dynon converters from Aircraft Spruce.

I've since drained the tanks. Had to do fuel flow test anyway.
 
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