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I've seen this question. But that's aimed at connections that see rain/spray.

I've got a 4-20mA sensor which I want to submerge in up to 35m of water. The sensor, unfortunately, comes with a 5m cable. So I'll need to make a waterproof connection that can survive submersion up to 30m and is insulated well enough that leakage current is insignificant compared to 4mA. I have the added requirement that the water is potable and so any solution should not pollute the water - must be food safe.

Suggestions on the other question are:

  • Grease-filled wire nuts - these seem to me to fail the food-safe requirement.
  • Grease-filled IDC - likewise.
  • Adhesive-lined heatshrink - not sure on the food safety or the waterproofing at that depth.
  • Adhesive-lined crimp/solder splices - likewise.
  • Packing the connection in silicone - this looks the most likely to me, so long as a food-grade silicone is used.

Another possibility that occurred to me is to pack a solder join in epoxy.

Any other options?

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  • \$\begingroup\$ How do they do it for under-sea power and comms cables? There must be some data somewhere. I would personally go for the adhesive lined heatshrink, 35 m of water will do a lot of diluting of anything leaching from the glue. As your leakage is only with respect to 4 mA, that's a very low bar to meet. I've just redone my flat roof with a polyurethane resin - now that stuff sticks to almost anything. \$\endgroup\$
    – Neil_UK
    Aug 12, 2022 at 13:26
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    \$\begingroup\$ If the sensor only comes with 5m cable, are you sure it is waterproof to 35m? \$\endgroup\$
    – bobflux
    Aug 12, 2022 at 13:30
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    \$\begingroup\$ I can't comment on food safety, but I've successfully used adhesive-lined heatshrink for sensors at 100m depth in seawater with no trouble. \$\endgroup\$
    – brhans
    Aug 12, 2022 at 13:31
  • \$\begingroup\$ Presumably the sensor is suitable for a potable water application and carries a rating from NSF, AWWA, or the equivalent organizations in your country or area. What does the sensor manufacturer say? What is the sensor measuring? Is this 35m below ground, or is it a tall vessel where the sensor could be installed in a port with wiring on the outside? \$\endgroup\$
    – Theodore
    Aug 12, 2022 at 13:45
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    \$\begingroup\$ @bobflux that could be done, but I think the pipe would gradually fill up with water. Not so much from leaks as from condensation. \$\endgroup\$
    – Tom
    Aug 12, 2022 at 16:04

1 Answer 1

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Terminate that cable with an Immersion, Dry mate connector and make an extension cable terminated with the mate to that connector.

These are connectors with a rubber housing. They are mated on dry land, which seals them, and then immersed.

TE Seacon connectors {TE Connectivity}

List of dry-mate connectors (my site):

  • MANUF. - SERIES
  • Amphenol Industrial - Submariner 5500 - 15
  • Amphenol Industrial - Submariner 5500 -20
  • Cooper - Eaton - Burton Dry-Mate 15
  • Cooper - Eaton - Burton Dry-Mate 16
  • Cooper - Eaton - Burton Dry-Mate 20
  • Cooper - Eaton - Burton Dry-Mate 24
  • Cooper - Eaton - Burton Dry-Mate 32
  • Cooper - Eaton - Burton Micro-Dry-Mate 12
  • Cooper - Eaton - Burton Micro-Dry-Mate 9
  • Lemo - 03
  • Lemo - 0V
  • Lemo - 0V uni
  • Lemo - 0W
  • Lemo - 1V
  • Lemo - 1W
  • Lemo - 2V
  • Lemo - 2W
  • Lemo - 3V
  • Lemo - 3W
  • Lemo - 4V
  • Lemo - 4W
  • Lemo - 5V
  • Lemo - 5W
  • Souriau - M-10
  • Souriau - M-14
  • Souriau - M-20
  • Souriau - M-24
  • Souriau - M-9
  • Souriau - MU-10
  • Souriau - MU-14
  • Souriau - MU-20
  • Souriau - MU-8
  • Souriau - SWIM-14
  • Souriau - TP-10
  • Souriau - TP-14
  • Souriau - TP-20
  • Souriau - TP-8
  • TE Connectivity - GLOBE-CON - G
  • TE Connectivity - GLOBE-CON - K
  • TE Nanonics - QCM FCM
  • TE Nanonics - TCM
  • TE Seacon - HUM - G
  • TE Seacon - HUM - K
  • TE Seacon - HUM - L
  • TE Seacon - Seacon 55 - 15
  • TE Seacon - Seacon 55 - 16
  • TE Seacon - Seacon 55 - 20
  • TE Seacon - Seacon 55 - 24
  • TE Seacon - Seacon 55 - 32
  • TE Seacon - Seacon CS-MS - J
  • TE Seacon - Seacon CS-MS - K
  • TE Seacon - Seacon LMG LSG
  • TE Seacon - Seacon MINI-CON D
  • TE Seacon - Seacon MINI-CON G
  • TE Seacon - Seacon MINI-CON K
  • TE Seacon - Seacon MINI-CON M
  • TE Seacon - Seacon RMA XSA XSB XSC
  • TE Seacon - Seacon RMF XSF
  • TE Seacon - Seacon VMA VSA VSB
  • TE Seacon - Seacon VMF VSF
  • TE Seacon - XSEE MSXEE
  • TE Seacon - XSJJ MSXJJ (hybrid)
  • TE Seacon - XSL MXSL
  • TE Seacon - XSM MSXM
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