Eloy, Neither shrink wrap or standard cat 5 jackets or insulators are impervious in general. This is generally measured with water at pressure. Impervious jacket cables are available, and many of them also have goo inside to prevent lateral moisture travel in the cable.
IMO, the easiest thing to do is put the whole cable in a PE (polyethylene) or PEX tube and stick the senor out the end. There are lots of options for sealing, but I put my vote with alcohol cure RTV (silicone.) As said before, I stay away from the acetic acid curing RTV that you get in the hardware store. If you want, I can find you a Dow part number for an example. For protecting the sensors, I really like the stainless steel tubes with one end rolled closed. You cut them to length, stick the sensor inside with some thermal paste and back fill with RTV the best you can (if you can get a very large gauge syringe and needle, it works great.) The thermal conductance of stainless is not that great, but the walls are so thin it doesn't matter. If it's an air measurement, clip a heat sink on the outside of the stainless tube. If you are going to use conformal coating, you need to clean ALL the flux and dirt off first. The stuff comes in cans and sticks to everything, so gloves and lots of old newspaper are recommended. I have used this to go through environmental testing where water was running off the boards (the dummies did the cold test first and then the humidity test...) just my $.02. jerry On 03/02/2011 06:49 PM, Eloy Paris wrote: > Hi Paul, > > On 03/02/2011 05:49 PM, Paul Alfille wrote: > > [...] > >> 3. The wine cellar uses a DS18S20 in a plastic drinking straw with >> some GE RTV silicone sealant (from the hardware store) sealing the >> end. It's been immersed and functioning for 6 years now. > > Wow, that's great! I wasn't too lucky with my first attempt (it got wet > inside). I'll keep trying, though. > > By the way, related question: is heat shrink supposed to be waterproof? > I mean, if I heat-shrink a tube, can I leave it submerged? > >> Maybe some static charge in the Vcc lead confused the sensor in the >> lightning storm? > > You know what, I want to get to the bottom of this so I have decided to > do nothing now to try to fix the problem I experienced a couple of > nights ago when we had lots of rain and thunderstorms. Allow me to explain: > > Whatever happened a couple of nights ago surely will happen again. When > that happens I'll go outside and start with the simple stuff, i.e. > grounding Vcc. I am hoping that the problem was caused by either high > humidity, or by some weird electric problem caused by not having Vcc > grounded. If it is the later I will be able to confirm it by grounding > Vcc when the problem is happening. As I said, I have not had a single 85 > degree reading since that night, so I have no need to try to fix things > right. > > I'll report back as soon as I know more. > > By the way, thanks to everybody that have provided useful links and > shared their war stories; it's been a very enlightening discussion. > > Cheers, > > Eloy Paris.- > > ------------------------------------------------------------------------------ > Free Software Download: Index, Search& Analyze Logs and other IT data in > Real-Time with Splunk. Collect, index and harness all the fast moving IT data > generated by your applications, servers and devices whether physical, virtual > or in the cloud. Deliver compliance at lower cost and gain new business > insights. http://p.sf.net/sfu/splunk-dev2dev > _______________________________________________ > Owfs-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/owfs-developers ------------------------------------------------------------------------------ Free Software Download: Index, Search & Analyze Logs and other IT data in Real-Time with Splunk. Collect, index and harness all the fast moving IT data generated by your applications, servers and devices whether physical, virtual or in the cloud. Deliver compliance at lower cost and gain new business insights. http://p.sf.net/sfu/splunk-dev2dev _______________________________________________ Owfs-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/owfs-developers
