Calibration fuel - Dynon converters

[smaragd]

I calibrated de fuel system but I think that does not work right.-

The plane is a RV-7 with a D-120 Dynon ( besides a 100, HS-34, the two SERVOS and AP-74)
The tanks are build as VANS indications.-

There are put two Dynon converters.-
Measure the BNC conector, there is not continuity between the center and the ground, as correspond in both tanks
I also checked the conections and the converters come to the 12V

The point is that when I star the test, the system ask the tank capacity (21g o 79.5 lits)

Then ask to fill the tanks with 10 lt steps, I mean in eight phase.-

So the voltage variation and also the units that shows the D-120 is very small.-

It’s supose that the converter must gives a referecte tension of 0 to 5V (From empy to full), but only change just a little mV in each charge, I mean, in each step of 1/8 charge.-

The own system says that the variation is very small and ask for a confirmation that the fuel is really add.-

Finally, says that the operation was a success, but the voltage difference that gives the converter from empy to full is al least of 0.5V, that means 10 times smaller that really has to do

What I have to do with this?

My regards and, advenced, thank you very much

Roberto Buonocore - Argentina

 

[dynonsupport]

The converter doesn't necessarily convert to a full spread of 0-5V. In fact, it's usually quite a bit less. If you're seeing the warning messages, you might be on the threshold of detectability with your setup. The real test is whether or not the fuel gauge works reliably. A .5 spread is on the small size, but may well work just fine. You might try draining a tank to see if it works alright.

 

[Edwardoc]

In doing the calibration on my capacitance fuel system, the wizard would direct to enter the tank capacity and select next.  It then directed to add 2 gal of fuel and press ADD.  On the next 2 gal fuel added, I pressed ADD and it would state " There was no change in the voltage reading and did I want to accept the reading anyway.  In looking at the voltage readings, there was an increase from 1.01 to 1.05.  The first one was from 1.01 to 1.05 and the next 2 gal read 1.07.  At 20 gal it was reading 1.38.  But it always stated there was no increase and did I want to accept the reading.  Is this normal for the wizard.  Very misleading if you don't know it is going to do that.

 

[dynonsupport]

When the change is very small, like it is in your case, it throw that warning. Basically, though, as long as you're actually seeing a change with each step - and it sounds like you are - you should be OK. It's essentially noting that the change is very small.

 

[salterjw]

You might try draining a tank to see if it works alright.

As a newcomer to this forum I am trying not to ask questions that have already been asked. Regarding the quote above.. Does it matter at what rate the tank is drained? Does it have to reflect the rate that the engine would normally consume the fuel? I hope that my first question is not a dumb one.

 

[mmarien]

I think he means draining a measured amount of fuel and see if the gauge reflects what you have drained. If you had 10 gals in the tank, does the gauge show two if you drain eight. How you drain it doesn't matter. You just want to make sure the gauge accurately shows what is in the tank.

 

[salterjw]

Thanks Murray, I am finding that my fuel gauges (using Dynon "Cap/voltage " converters) become increasingly inaccurate as the tanks drain towards empty. There are prolonged periods when the gauges do not register any change despite 10 litres or more leaving the tank. Then suddenly they catch up -(but not completely) Thereafter they over-read until empty. (Not good for my peace of mind!!)
I was wondering if the rate of draining (one litre at a time through the fuel drain) was too fast for the Dynon EFIS. It is approx. 30litres per hour.

 

[Dynon]

So the fuel level gauges do have some filtering to even out sloshing. Now, assuming you have SkyView - we've improved them over time, as you can see in the update notes for both the sensor definitions themselves and SkyView software. So first, make sure you have the latest software, and the latest sensor definition file. Then, note that there are two characterizations for capacitive sensors: normal CAPACITIVE, and CAPACITIVE SLOWER RESPONSE. In your case, make sure you're using the regular "CAPACITIVE" definition (selected in your pin mapping page), which is faster than older versions of the definition.

 

[salterjw]

Thanks for the clarification. I have a Dynon Flight Deck D180. Does that make any difference?

 

[dynonsupport]

Yes, unfortunately. The changes mentioned in the previous post have not been implemented in the FlightDEK-D180. But, I believe (I'd need to do more research to be sure) that the response rate to changes in the D180 is faster than either profile available in SkyView.

In Tech Support, we've (anecdotally) observed that fuel level sensors can seem (note - CAN... SEEM TO... not necessarily EVERY FUEL LEVEL SENSOR DOES...) change their output over time ("drift"). We don't know why, for sure, but some guesses:
* The resistance of the float changes slightly
* The actual float isn't quite so buoyant as it was when there was no fuel in the tank (leakage into the float?)
* The float arm gets bent, changing the resistance per fuel level
* Some mechanical resistance develops in the float arm so it sticks a bit in certain positions and then "frees up" when enough movement / buoyancy / time is applied
* Capacitance fuel level sensors DO sense fuel level differently if a different fuel is used than what they were calibrated with
* Perhaps a film develops on capacitance fuel level sensors that changes the base capacitance
(Again - these are guesses.)

Some customers I've talked to have adapted to this by draining the fuel tank at their annual, and re-doing the fuel level calibrations as part of their annual, and note more accurate fuel level display.

Thanks for the clarification.  I have a  Dynon Flight Deck D180. Does that make any difference?

 

[salterjw]

Thanks for the reply. I do not have float equipped tanks. The tanks contain "capacitance plates". They have only ever been calibrated against Avgas and as the aircraft has not yet flown the chances of film developing on the plates is low. Could you confirm that these voltage converters are actually manufactured by Electronics International. I ask because Vans told me to contact them as Vans do not support Capacitance Fuel Senders any more. I have done so and I want to be sure that I am not confusing the issue by talking to the wrong people. Many thanks Jeff

 

[salterjw]

I should have given the part numbers.

Dynon part No 100654-000
Vans part No EI P-300C

Are these one and the same unit or different units?

 

[dynonsupport]

The capacitance-to-voltage converters sold by Dynon Avionics are manufactured by Dynon Avionics specifically for the Van's Capacitance Plates. They're not supported for use with any other cap

As we state frequently here on the Forum, if you have a specific issue, with a specific aircraft, you'll get better support by working directly with our Technical Support group - 425-402-0433, or support AT dynonavionics DOT com.

Thanks for the reply. I do not have float equipped tanks.  The tanks contain "capacitance plates". They have only ever been calibrated against Avgas and as the aircraft has not yet flown the chances of film developing on the plates is low.  Could you confirm that these voltage converters are actually manufactured by Electronics International. I ask because Vans told me to contact them as Vans do not support Capacitance Fuel Senders any more. I have done so and I want to be sure that I am not confusing the issue by talking to the wrong people.  Many thanks  Jeff      

 

[dynonsupport]

I can confirm that 100654-000 is the Dynon Avionics P/N for a Capacitance to Voltage Converter for Vans Capacitive Plates. I cannot confirm the Van's P/N is a part supplied by Dynon Avionics... though I'll hazard a guess that the "EI" prefix indicates that the Van's part is NOT the Dynon Avionics part.

I should have given the part numbers.

Dynon part No 100654-000
Vans part No  EI P-300C

Are these one and the same unit or different units?

 

[Dynon]

And just to follow up, that EI part has a frequency (square wave) output. SkyView can only read a 0-5V variable voltage output, where the voltage itself is the signal. SkyView is not compatible with that EI converter.

 

[salterjw]

That is what I thought. Thank you very much. I have opened dialogue with Dynon Support.