Sonex Fuel Tank Calibration

[bakfly]

Hi All, I wonder if anybody can help? I tried to calibrate the Fuel Tank level sensor this afternoon without success. The probe I am using is a Sonex bought Princeton Capacitive Fuel Level Probe. The Probe is connected to a black box, written on the box is do not calibrate, calibrate on the Stratomaster. I tried to calibrate it in the MGL Enigma but it does not work. After selecting Fuel Tank setup menu and then Fuel Tank Calibration RDCA 1 Tank 1, I expect the Current tank raw level reading to change after putting fuel in the tank but the reading stay put on 27. I also tried to open up the Fuel level probe black box to have a look inside but I can’t open it. The instructions what came with the probe shows lights and a button inside but because it is already calibrated maybe I don’t need to open it. Does anybody know what to do about it? Thank you, Peter Sonex 1430 :roll:

[gammaxy]

I'm also trying to troubleshoot a problem. I get raw readings of about 1000 that seem to change when I add fuel (I've only added 2 gallons so far). But they slowly drift so after a while my reading at 2 gallons might be the same as 0 gallons. Princeton recommended I double check my grounds, but I haven't yet.

I hadn't put too much effort in since I wasn't sure if should even work as low as 2 gallons.

Have you checked the pull-up resistor settings on the RDAC?

EDIT:

I've now been flying with mine for about 7 months and it works pretty well. The readings that are saved seem to be accurate to within about 0.5 gallons. Mine is calibrated pretty well in the tail-down position and seems to read about 2 gallons lower in flight. I cross-check it against the marks on my fuel tank before each flight and it is always correct now (at first I didn't calibrate it very well in the mid ranges, so I spent a few minutes after a few flights changing the calibration at progressively-lower fuel levels).

I haven't noticed the drifting problem I mentioned before, but I never have less than 2 gallons in the tank now that I'm flying.

[bakfly]

Hi Chris, yes I checked the pull-up resistor setting on the RDAC, it was on but even after turning it off nothing changed. Next time I am going to the hanger I will checked the wiring first.

[Rick524]

I have the Sonex/Princeton probe. Didn't have any luck calibrating it.
I had a Centroid probe that came with the Enigma, that is meant to
replace Cessna style senders. I cut the black box off the Princeton
probe and separated the Centroid module from its probe then joined
the Centroid module to the Sonex probe. Calibrated fine. Very stable
with repeatable readings.

Rick
Sonex 524

[Gripdana]

I am having the same problem with mine. I tried to calibrate exactly per the MGL/Sonex instructions. I get nothing. I have the MGL Extreme and MGL RDAC. When the pull up resistor is on I get a 2671 reading that never changes and with it off I get 0. All connections are good. I have not tried to change the filter setting in the fuel setup menu yet. I tried to call and e mail princeton to get help but they never answer the phone during the time they say you can call and "talk" to someone. I tried to email them and no reply at all. I bought this probe new from another builder that went with another probe for his set up. I am ready to just buy another probe from Sonex and see if that works and put in a sight tube. Any help would be appreciated.

[kmacht]

It has been the same problem with mine. It reads 1227 no matter what the fuel level is. I thought it was because I was using auto fuel but maybe not since others are also having the same issue.

Keith
#554

[sonex892]

Confirm the probe and is grounded properly back to the instrument ground. Not just the airframe.

[Gripdana]

I confirmed all power and ground connections and all are good. My black box has 2 outputs one is for resistive which is green and one for capacitive which is yellow. The old Sonex instructions from 2008 sez to use the green one for the stratomaster but I have an Extreme EFIS and I think it requires capacitive information. The Princeton instructions said to only use one either green or yellow. Does anyone know for sure?

[Gripdana]

Well I talked to MGL and he said to go ahead and try the capacitive lead and turn off the Fuel Level PU on the RDAC. So I tried that and had no luck. I have sent emails to Princeton and MGL with details of what I have done so far. I hope to get this to work. I do know this thing ties the cowl and canopy for the most frustrating thing so far. Maybe I will just use it to plug the hole and install a sight tube.

[Gripdana]

I finally got the probe calibrated. I had purchased another probe from Sonex and it would not work. Then Princeton sent me a warranty replacement on the first probe. I had installed the probe from Sonex. It was a little long so I trimmed about 3/8" and hooked up the box. I tried and tried to get it to work. Finally I got the second new probe from Princeton and was able to talk to Todd from Princeton while troubleshooting. The new version of the probe had a plug on the shielded wire to the probe so I used a molex connector for the other leads on the box. This made for a quick and easy troubleshooting. The results were a bad black box. The probe was good so I used the probe that came from Sonex and switched out the box then was able to set all the points for the MGL Extreme to read the fuel level. Todd told me he would refund me for the probe I bought from Sonex. Thanks to Todd from Princeton for the great customer service.