Making electrical connections to a carbon fiber tube?

[e100]

I have some 22mm and 10mm carbon fiber tube left over from another project and because of its corrosion resistance I was wondering about using it to make a capacitive liquid level sensor for use in salt water. I'll insulate the inner tube and leave the outer tube in electrical contact with the water. The salt makes the water behave like a dead short so the dielectric will be the insulation layer covering the inner tube.

I searched on Google but couldn't find any fittings designed for making electrical connections to carbon fiber. It's brittle so conventional fasteners aren't going to work. The current is only going to be milliamps, but the connection resistance needs to be consistent over time.

I had a look at silver loaded epoxy but that is super expensive at $150 for 15g and I'll probably only use 10% with the rest going to waste.
Would brass wire wool or EMI conductive rubber under a hose clamp work?
Would double sided conductive copper tape give a consistent connection over time?
 

[David Hess]

I have had good results with a mechanical connection using a machine screw and star solder lug but I am not sure how to apply that to such a small diameter tube.

[T3sl4co1l]

Sand the surface to expose fibers, then wrap with a hose clamp?

Tim

[duak]

I'm not sure where you are but perhaps a trip to a local plumbing store to look for Compression Fittings.  These are fittings for tubing where a metal or plastic sleeve or ferrule slips over the tubing and is then locked in place by a nut with a tapered center hole.  These compress the tubing radially and I think if not overdone will not damage the tubing.  Here in Canada, they are available in brass, chromed brass and stainless steel.  Since you are working with salt water, there might be some electrochemical effects from the metals of the fittings.  I believe stainless or chrome will be the most salt water resistant, or will at least balance out any effect if the same metal is used at both ends.  It might make sense to find a polymer fitting and find a metal sleeve or ferrule that you can connect an insulated wire to to keep the connection away from the salt water.

Cheers,