[PSUBS-MAILIST] Sonar thru hull wiring

Mon Jun 24 15:45:00 EDT 2019

 I think they can't hurt.  The idea is to supply a less resistive path to ground for any inductive noise that might be picked up either through motors or other cables.  Shields have more surface area and less resistance than the signal wire so the inducted noise will take that path rather than the signal wire.  The proper method is to connect the shield separately to a dedicated pin that ultimately ends up on ground of the power supply.  So, as has been suggested by others...if the transducer has three wires, get a four pin connector and apply shield to the fourth pin and then terminate to your battery ground somewhere inside the hull.
Jon

    On Monday, June 24, 2019, 03:32:39 PM EDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Brian,I did a quick Google on shielded cables & I can't see that they are ofany advantage in our situation. Unless you are running them next toanother cable. Perhaps more of an advantage inside the hull.Maybe with saltwater being a conductive medium there is more chance ofElectrical interference, but I don't know.Anyone got any thoughts on this?Alan

On 23/06/2019, at 1:05 AM, Brian Hughes via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Alec, that's how I ran my prior transducers, but ...

As I haven't yet cut through the wiring I don't know for sure, but I suspect it's more than the usual two, hence the question. I'm debating attempting the simplest approach: tie a tight knot in the cable and run it through a 90° elbow, the part facing out being at least 1/2" larger than the thru hull.  I have an extra 1/4" NPT I could use.  Plug the narrow end with epoxy, and top the large end with 2 part hard rubber.  I know Mark does this with his subs, but he dives shallower than I'll be going.

Hmm ... or maybe a gland tightened around the cable, same deal as above, but embedded the gland base in the 2 part hard rubber. Or maybe a stainless cap tapped for the gland base, and fill with hard rubber from the other end. I used to make canister dive light heads that way, using turned down D cell mag light heads with LED replacement bulbs. Hmm ...

I can shorten internally and splice correctly.

Reflections?

Brian

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