Capacitance plates touching proseal

[Vansrv7arob]

Just installed my capacitance plates and the in board right is just touching (1/32 inch) the proseal, yep, there's allot of proseal over those heads.

Is this going to significantly affect the function or accuracy good clearance on the rest of them.

Anyone else had this issue what was the outcome?

 

[Brantel]

You can trim the plates to clear anything they may touch. Due to the difficulty in fixing this if it does not work, I would make sure they don't touch anything.....

 

[Vansrv7arob]

Care to explain how this may effect capacitance readings?

Just stuck the multimeter on the proseal, same capacitance as air?? And open circuit on all checks of plate isolation, what gives?

I know you have great electronics knowledge Brantel, can you explain why this may be a problem?

Cheers,

 

[BobTurner]

You have a fancy multimeter if it measures capacitance.
I don't think this is an issue now, but I would worry about vibration allowing the plate to work its way thru the proseal to the metal rivet.

 

[Brantel]

I have never tested Pro-Seal to see what its dielectric constant is nor do I have a spec sheet that details it. The capacitance levels that these senders work at is very small and it is difficult to accurately measure with a typical handheld multimeter (even one that measures capacitance). I can't tell you what the effects will be if any at all since when you start working in capacitance values this small, it is just as much art as it is science with a little black magic thrown in for good measure.

I would lean to the more conservative and cautious side in this matter just to ensure that there are no issues. Once you seal that tank up, it is hard to fix issues with the capacitive senders.

 

[Vansrv7arob]

You have a fancy multimeter if it measures capacitance.
I don't think this is an issue now, but I would worry about vibration allowing the plate to work its way thru the proseal to the metal rivet.

I don't know, it say capacitance, I stuck it on delta mode, and proseal same capacitance as air, I would presume fuel wet proseal would be different.

But come to think of it, I prosealed the back of my connectors which are obviously connected to the plates, the proseal tails are long as suggested to prevent seepage to bnc center pin, these tails extend through the vent grommet so I guess the plates are effectively touching at these point as well.

The plates are also connected although isolated through the plastic washers and tubing over the screws?

Maybe I'm screwed.

 

[Brantel]

Rob,

If you have already mounted your plates and have gone so far as it would not be easy to trim the plates, I would just make sure there is not any conductivity between the plates and the tank and hope for the best. I am pretty sure cured pro-seal is not conductive so you should be ok in that regard.

If the plates are ever shorted to the tank whatsoever, they will not work.

 

[Vansrv7arob]

I'll trim the proseal I guess, plan was for a fuel flow meter any how.

Thanks for your input Brantel, love your plane, how's the new panel going?

 

[Brantel]

I'll trim the proseal I guess, plan was for a fuel flow meter any how.

Thanks for your input Brantel, love your plane, how's the new panel going?

Thanks and I am loving the panel more and more each flight! We live in amazing times! It feels good for a retired airline captain to look at your panel and drool!

 

[rzbill]

Hi Brian,

I have a meter specific for capacitance. When I was fooling around with building my own freq to voltage convertors (per Weis, Kitplanes), I measured my tanks empty. 180 picofarad. So you are right, it is pretty meager. I would go to all effort to make them perfect due to the low value.

The tribal knowledge was that it would double when full of avgas. I have never measured them in that state since I bought the Dynon convertors like you did.

They work pretty well actually. I curve fit the EIS for the lower half of the tank to read right. I never have done the work to get the upper half spot on but its closer than any spam can I ever rented.