fuel levels read high

[cjohngraham]

I have a RV-7A and HDX and capacitive fuel senders. After calibration, the fuel gauges gave reasonable readings before and after a flight, within a gallon or two of what was in each tank. Now, the readings will come up to a fairly accurate level after fuel is added, but thereafter only go down a gallon despite several gallons being used from a tank. E.g. after today's flight, gauges said 12 gallons in each tank when only 6 were left in each. We're in Phase 1 with about 21 tach hours. Hopefully there is a way to achieve better accuracy.

 

[Dynon]

It should "just work", but on some installations, the voltage ranges can be tight. Do you know what the differences in voltage are across your data points (you can go back into the fuel calibration menu to see a table readout of the voltages stored for each gallon measurement.)

 

[cjohngraham]

The voltage difference for each 2 gallon increment is very small, .01-.03 V, in a couple of cases zero. Would it do any good to go through the calibration process again? It's puzzling that the gauges respond appropriately when fuel is added but not as it is used.

 

[mmarien]

The capacitive sensor in my Glasair is a single tube. Pitch affects the reading. I ended up calibrating a few times (for different reasons), but on the last calibration I used the Skyview attitude indicator to level the airplane in cruise attitude before I calibrated. That way the gauge was accurate in cruise. It reads different when on the ground. And in climb or decent.

Some of the differences in the calibration are only 0.02 but the numbers are to six places.

 

[Dynon]

Maybe, but not certainly. Do you change the type of fuel that you use (IE 100LL and/or mogas)? Different fuels have different capacitances, and that can affect readings.