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I have the Princeton (Now R.E.D.) capacitive probe and a red cube fuel flow sender in my A series with a CAMit 3300 and a GRT Sport SX. . Both the actual and calculated fuel levels are very close together at all the way to the end. The capacitive probe is not accurate if you use multiple grades of avgas/mogas. But have no info on how the capacitive sensors may work in metal tanks.

David A.

If the calibration process was done exactly per instructions, the levels were very accurate and I never had cause to second guess them. Of course, I always cross-checked them with the calibrated fuel flow readings at every fill-up.

bvolcko38 wrote:I have an MGL efis with sonex supplied probe. I calibrated with 100ll. Using 90 or 91 non ethanol, my fuel gauge reads about 2 gallons low.

Better low (pessimistic) than high (optimistic) but 2 Gall ( 7.6L) seems a tad inaccurate for our small aircraft/fuel tanks.

I am sure you would have done a recalibration with no improvement - could this be a MGL issue rather than a sensor problem?

I think its an electro-chemical issue. 100ll has different properties from 90 non ethanol. I could re calibrate with non ethanol.

Skip. Australian fuels may have more similar dielectric properties. I have been using both Avgas and 98 octane (90% 98 octane) with this probe for 13 years now. Have never seen difference in level readings when alternating or mixing fuels. I use a calibrated dipstck to confirm fuel level preflight.

bvolcko38 wrote:I think its an electro-chemical issue. 100ll has different properties from 90 non ethanol. I could re calibrate with non ethanol.

Now I understand - the small inaccuracy may be due to differing fuels. - Thanks.

sonex892. wrote:Skip. Australian fuels may have more similar dielectric properties. I have been using both Avgas and 98 octane (90% 98 octane) with this probe for 13 years now. Have never seen difference in level readings when alternating or mixing fuels. I use a calibrated dipstck to confirm fuel level preflight.

Thanks for that - Sounds to me that the RED/Princeton probe is a reliable & consistent fuel sensor -just what I need to help with in flight fuel management.

Like you, I would never take flight without a physical (calibrated dipstick) check on fuel quantity.