Question for the electrical cognoscenti

[daveyator]

I’ll ask the question here, as I’m talking about an RV12, but it could also fit into the Comm forum. Anyway, here goes.
I dutifully checked that all my headset jacks were properly isolated from the airframe as described in the KAI.
I’m approaching the final stages of the build, and rechecked them, to find them all earthed to the airframe. Not being an electrical whizz, I did the obvious, and went into a panic. Then I found that even if I removed the jacks and held them away from the airframe, they were still earthed. After disconnecting the wiring, I found them to be properly isolated from the frame. Is this how things are meant to be?
As I said, I’m no electrical genius, so could someone put my fears to rest and give me a brief explanation of what I’m seeing here. Be gentle.
Cheers DaveH
120485

[wirejock]

Originally Posted by daveyator

I’ll ask the question here, as I’m talking about an RV12, but it could also fit into the Comm forum. Anyway, here goes.
I dutifully checked that all my headset jacks were properly isolated from the airframe as described in the KAI.
I’m approaching the final stages of the build, and rechecked them, to find them all earthed to the airframe. Not being an electrical whizz, I did the obvious, and went into a panic. Then I found that even if I removed the jacks and held them away from the airframe, they were still earthed. After disconnecting the wiring, I found them to be properly isolated from the frame. Is this how things are meant to be?
As I said, I’m no electrical genius, so could someone put my fears to rest and give me a brief explanation of what I’m seeing here. Be gentle.
Cheers DaveH
120485

The ring is ground. The reason for isolating is to prevent a ground loop. You want ground to follow the correct path and not take the path of least resistance through the jack to ground. That's my unedumacated opinion.

[BobTurner]

The jack is isolated from ground, but the ‘ground wire’ from the jack is connected to ground at the audio panel. If the jack were not isolated from ground, some of the current would travel thru the airframe, mix with other ground currents (like alternator return), and you might hear ‘alternator whine’ in your audio. Your dc meter doesn’t care about the different paths, so it shows any/all portions from the outer part of the jack to the audio panel connection all connected (eventually) to ground.

[Mich48041]

Is this how things are meant to be?

Yes, not to worry.

[daveyator]

Thanks for the replies. I can sleep tonight
Cheers DaveH