I posted a message about creating a tube and closing the end off with silicone. That would be okay as the part that is sensitive is the jacket for the wire and not the metal tip. Likewise the wire is not exposed to the silicone plug while the silicone is wet. In fact, I waited a week or more to be sure the silicone was fully cured. AND, if still concerned a small wad of paper or cotton ball can be pushed down the tubing ahead of the metal sensor and keep the entire works away from the silicone. I didn't do that because silicone isn't reactive with aluminum... if it were, I'd have drowned in my sailboat a long time ago as many of the fittings were waterproofed with silicone LOL. But, protecting the plastic sheath of the probe from silicone is important as that is reactive. But, all it takes is letting the stuff in the end of my homemade tube completely cure and then placing a small wad of paper or cotton in it as a spacer.