AFS3400/Dynon Capacative senders/Fuel Readings

[Steve Sampson]

Brian, thanks for that clarification. I did not see the converters mentioned, but I will look again.

Randle, your comments are practical and helpful. I am flying home on Friday but think the idea of tapping on the converters with the system powered up is a good one. With no bad joints in the wiring system I struggle to believe I made two in the fuel system, so do keep returning to the converters as the probable cause. However no one else is saying they have had them as a problem. Being in the UK a chat with Dynon is expensive also, but perhaps I can Skype them. In the end cheapest might be a new converter to see what introducing that does. The problem that is really hard to prove is a loose connection inside the tank. Perhaps next time I fly I should do lots of uncoordinated flying and see if that has an effect.
Thanks for the interest....its helpful. Steve.

[rzbill]

Go to the Appendix 7.1 of the EMS-D120 Installation guide and you will see that the Dynon Freq to Voltage convertor needs to be supplied with 12 volts. You said 5v in an earlier post. Make sure it is 12.

(10 to 15v per document) Over 15 causes damage. Standard aircraft bus 12v is probably not good enough to keep these things stable.

I have mine powered by instrument quality regulated 12v out of my GRT EIS 4000. No Problems.

It outputs 0 to 5 volts back to the EIS input for gage reading.

[Randle]

Originally Posted by rzbill

the Dynon Freq to Voltage convertor needs to be supplied with 12 volts. You said 5v in an earlier post.

This is the best thing I think you have to go off of so far, have you checked into it or talked with Dynon?

[Steve Sampson]

Originally Posted by Randle

This is the best thing I think you have to go off of so far, have you checked into it or talked with Dynon?

Randle, it will be getting the correct voltage, just my memory faulty there. I had a PM from another to say he had the same problem.

[dynonsupport]

They really do need to have 12V, not 5V. I just looked at the schematic and they are regulated to 5V inside, so if you feed them 5V they will misbehave. Regulators need more input voltage than their output to regulate properly.

They can take "noisy" aircraft "12V" just fine. They are fully regulated inside as long as you give them at least 7V and less than 15 they should work. Like all Dynon equipment, they are designed to handle the >15V spikes that an aircraft bus sometimes has.

Otherwise I'm a bit stumped as well as how something could affect both units at once.

--Ian Jordan
Dynon Avionics

[Steve Sampson]

Originally Posted by dynonsupport

They really do need to have 12V, not 5V. I just looked at the schematic and they are regulated to 5V inside, so if you feed them 5V they will misbehave. Regulators need more input voltage than their output to regulate properly.

They can take "noisy" aircraft "12V" just fine. They are fully regulated inside as long as you give them at least 7V and less than 15 they should work. Like all Dynon equipment, they are designed to handle the >15V spikes that an aircraft bus sometimes has.

Otherwise I'm a bit stumped as well as how something could affect both units at once.

--Ian Jordan
Dynon Avionics

Ian, they are certainly getting the supply from the aircraft bus, a very steady 14.6V. I just remembered they operated at 5V and could not remember where the voltage was dropped. So the supply voltage is a red herring.

So, have you not had other instances of symptoms as I described earlier. It happens on both tanks randomly. For a while it was only one tank, now both. No cross correlation. As I said before, another member here pm'd mme to say he had the same problem. Any simple tests I can do? Thanks.

[Dayton Murdock]

Hi All
In 2008, after I came back from Oshkosh I had the same issue with my capacitive sender?s .The repair was to cut large access holes in the rear baffles of both fuel tanks. Rewire the capacitive plates and replace the BNC connector, be sure to seal the wire ends with proseal and the BNC connector at the tank bulkhead. This procedure was omitted in the builder manual. The culprit for the inconsistent readings was fuel wicking up the wire and changing the capacitance. After enduring this repair procedure, I had 5 years of trouble free fuel readings, until now. My new system is exhibiting the same faults.

[Steve Sampson]

Dayton, I am pleased to hear I am not alone.

I just flew two legs, about 800 miles in total. The first leg both tanks behaved pretty well flawlessly. The second leg suddenly one tank dropped to about 27 litres, and then just before landing came back up to a correct reading of about 40. The other tank switched occasionally between zero and a correct reading.

I really would be pleased to hear something from Dynon.

Anyone else had the same problem?

[TIPSYNIPPER]

Hi All,

I am the new owner of G-IKON, and still have this problem......did anyone get to the bottom of it please?

Neil