Capacitive fuel senders, and problems with them

[DrillBit]

in the meantime, manually noting Zulu time for each tank switch and processing logged tank readings and fuel flows offline could eliminate the two gallons at a time fandango....

[Alan Carroll]

Originally Posted by airguy

And then there's that pesky 14 CFR part 25.1337 to consider...

Or not. I believe Part 25 only applies to transport category airplanes. There's also 91.205, but this applies only to aircraft with a standard category airworthiness certificate. As near I can tell there's actually no regulation that requires EAB aircraft to have fuel gauges? Not saying its a good idea, but I'd rather than a good totalizer than a bad fuel gauge.

[jimgreen]

I'm having trouble finding the Princeton capacitance to volts convertors.
Spruce sells the Princeton kits but they don't have the convertors as a separate item. Any ideas?

[longline]

Are the converters you are looking for similar to, or the same as, the Dynon converters? I have a set of Dynon converters that I will not be using.

[RV7A Flyer]

Originally Posted by longline

Are the converters you are looking for similar to, or the same as, the Dynon converters? I have a set of Dynon converters that I will not be using.

No. The Dynon converters have no capability of setting the voltages at the endpoints (empty/full), which the Princeton ones do (to ensure using the full 0-5V range, rather than the tiny portion of it that the Dynon ones use in this installation).

[wirejock]

Originally Posted by RV7A Flyer

No. The Dynon converters have no capability of setting the voltages at the endpoints (empty/full), which the Princeton ones do (to ensure using the full 0-5V range, rather than the tiny portion of it that the Dynon ones use in this installation).

Found them. I plan to use them as well. Stein does not sell them. GRT neither.
http://www.princeton-electronics.com...Converter.html

[rapid_ascent]

So I was thinking about the mix of fuels issue and the resultant inaccuracy of the sensor.

If the range is adjustable to allow for the variance in capacitance then as long as two fuels are calibrated separately then operating with either fuel should provide accurate results. When fuels are mixed this approach doesn't work. Depending on the majority of a particular fuel and the basis for the calibration then the errors will be smaller or larger. This error may be unacceptable in many cases.

Now what about if you had the ability to reset the full level either in your sensor converter or your measurement device. At full fuel level you have the maximum capacitance for the given fuel mix that is actually in the tank. This measurement could then be used as a scaling parameter for the actual calibration that was created when the tank was initially calibrated. The pilot could reset the full capacitance at any time to reapply scaling to the calibration.

No one that I know of allows this type of operation but it seems like it would resolve the fuel mix inaccuracy problem. I'd have to go through real calculations to confirm it, but it seems like it would work. Maybe a new software feature.

[N941WR]

Ray, check with your EFIS manufacture for the answer to your question.

With the Dynon (and others) you have to tell it you filled the tanks, although the gauges read a new level.

If they allowed you to enter the number of gallons in each tank, it would be easy for them to calculate a scaling number.

[rapid_ascent]

Bill, yeah exactly I think they could take care of this problem with a minor feature addition. I'm not super familiar yet with all the supported operations since my efis is a big open space at the moment.

[jimgreen]

Originally Posted by wirejock

Found them. I plan to use them as well. Stein does not sell them. GRT neither.
http://www.princeton-electronics.com...Converter.html

Thanks Larry, just what I need. Mind you, the price makes my eyes water, especially converted to Canadian mini bucks.