I'm looking at cable for some underwater sensors. Nothing fancy or mission critical, low current for low voltage pressure and temperature sensors, that sort of thing.
General specs are:
1) 4 conductors of say 0.25mm^2 to 0.5mm^2 + an overall shield.3) Withstand a few years exposed to UV in hot sunny conditions.
4) Withstand submersion in fresh or marine waters at up to 10m depth. 5) Grey or black sheath. 6) cost
I can comment on above-ground outdoor use of T&E & UHF co-ax. PVC, unless b lack, deteriorates from uv exposure. However a few decades in full sun only produces slight surface damage on grey T&E cable. White & brown co-ax seem to be less durable. IOW for best results you'll want black, but grey shoul d do IRL - other colours than black just can't be counted on to last decade s reliably.
NT
The biggest problem is going to be the seal between the sensor and the cabl e. I have seen silicone rubber used for hydrophones, with a gasket cavity about 50mm long. Avoid the type of silicone rubber which evolves acetic ac id when it cures, as this will corrode copper.
Don't rely on pressure to seal the wire, as the wire's insulation will cree p, reducing the compression pressure. You need to get a chemical bond or w eld.
So solvent welding a PVC chamber to PVC sheathed wire should work. Similar ly, silicone rubber is likely to bond well to silicone rubber sheathed cabl e and also to a glass or Perspex housing.
John
The biggest problem is going to be the seal between the sensor and the cable. I have seen silicone rubber used for hydrophones, with a gasket cavity about 50mm long. Avoid the type of silicone rubber which evolves acetic acid when it cures, as this will corrode copper. Don't rely on pressure to seal the wire, as the wire's insulation will creep, reducing the compression pressure. You need to get a chemical bond or weld. So solvent welding a PVC chamber to PVC sheathed wire should work. Similarly, silicone rubber is likely to bond well to silicone rubber sheathed cable and also to a glass or Perspex housing.
John
Take a look at Lexel adhesive caulk, it is clear.
I use it for bonding soles back on to shoes, filling cracks in wet areas and holes and bonding polycarbonate to polycarbonate.
I am just a user and not affiliated with anything related.
Let's see if CMXF, gel filled, shielded, stranded, direct burial, CAT5e will work.
That would #23 awg to #20 awg, which eliminates #24 awg CAT5e based cabling. CAT5 is #23 awg, so that will work. Want to revise your numbers a little?
That means stranded wire, not solid. Typical specs (they vary) for CAT5e is -10C to +75C, so that should work. However, some are +5C to +75C so don't assume all cables are identical.
In a past life, I designed marine radios, some of which ended up in the such places. The problem was not UV or heat. It was all the critters that just love to turn the cabling into their homes, or enjoy PVC for dinner. You'll need something with fungus protection.
14.5 psi. Direct burial cable is made to withstand 3 to 6 psi outside pressure (for laying inside pressurized conduit). I think you'll need gel filled cable, but I'm not sure.Black is best for UV protection.
Any oil or chemicals present? They can rot PVC jackets.
$0.20/ft will meet most of your requirements including gel (slime) filled.
Yep. The next step are the industrial cables, followed by various MIL-STD specifications for waterproofing, etc.
I have some experience, but not much. Better to check the spec sheet.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I founded and ran an oceanographic instrument company for 16 years. We primarily made deep sea and coastal-zone recording instruments.
A popular item consisted of underwater cables with sets of sensors molded in place. I had 30 employees; I'm sorry I've forgotten exactly how those were made, but I can say we quickly learned to use only rolls of a serious cabling meant for the purpose. These didn't have a gel, but featured very thick strong rubber sheaths. The raw cabling was not cheap. Cheap fails.
We used expensive underwater connectors, with molded machined-pin feedthroughs that don't let any water through. In this way we didn't completely rely on a cable's total integrity, it was allowed a little sea-water leakage.
--
Thanks,
- Win
If this is a commercial application get custom cables made and charge your customer accordingly. If there's any subsea engineering businesses near yo u location there will likely be companies offering cable bonding services, for example
Many thanks for all the replies and suggestions. Much to ponder!
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