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Weather Station Hardware => Davis Instruments Weather Stations => Topic started by: KC2TOH on September 28, 2009, 11:13:40 PM
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My Anenometer speed stopped working a few days ago, but the direction works fine.
I have the anenometer connected to the ISS with an extra 100' extension. This is all routed underground in electrical PVC. I took the junction box cover off and noticed that the box was filled with water. The connection between the two calble was totally submerged in water.
I shop vac'ed all the water out and dried off the connectors and I am waiting for the wind to blow to see if it works again..
Would the water intrusion cause the wind speed not to work?
I am hoping that this problem is caused by a wet connector and not something more complex.
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Definitely just a drop of water between the two speed conductors will disrupt the signal. The RJ-11 connector isn't waterproof, so some water may be inside the plug.
The direction may seem to work but may be wrong due to water affecting the resistance that the ISS sees. See diagram below.
If you leave the connectors open to dry air, in time they'll dry out.
Force air for a long time through the conduit to completely dry out all the moisture.
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Well I thought I sucked all the water out with the shop vac and dried the connectors off. Went all night and still 0 MPH wind speed. Either it isn't dry enough or the moisture caused something else to go bad. Could the mositure cause the reed switch or something in the ISS to go bad?
Definitely just a drop of water between the two speed conductors will disrupt the signal. The RJ-11 connector isn't waterproof, so some water may be inside the plug.
The direction may seem to work but may be wrong due to water affecting the resistance that the ISS sees. See diagram below.
If you leave the connectors open to dry air, in time they'll dry out.
Force air for a long time through the conduit to completely dry out all the moisture.
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If you have a multi-meter you could measure the cable to the anemometer using wxtech's schematic. This would give you an idea where to look depending on the readings you get. Other electronics could have been effected but I would imagine the problem is still in that water submerged junction area. Connectors, cable, etc.
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Check for corrosion on the connector pins or in the coupling. Maybe unplug and plug it back together several time to wipe the contacts.
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Well I took the junction box cover off tonight and it was filled with water again. I made a better suction and ended up shop vac'ing about 2 gallons of water out of the entire length of PVC. I would have never thought that water would ever get into the PVC and I have no idea how it is getting through.
I examined the 2 connectors and the coupler more closely and did notice a little corrosion. I used alcohol and scraped the corrosion off with a knife. Still no luck.
I looked through my Davis supplies I noticed that I never used the special waterproof kit with the waterproof crimp-style splice connectors that I received with the Davis extension cable. I was just using the cheap 6-Pin cable coupler.
Once I cut the old connectors off, removed the coupler and installed the waterproof kit everything is working fine now!
I just wonder how long this will work. The PVC is bound to fill up with water again. The waterproof crimp-style splice connectors do seem like they would work really well though.
Thanks for all the help.
Check for corrosion on the connector pins or in the coupling. Maybe unplug and plug it back together several time to wipe the contacts.
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Well I took the junction box cover off tonight and it was filled with water again. I made a better suction and ended up shop vac'ing about 2 gallons of water out of the entire length of PVC. I would have never thought that water would ever get into the PVC and I have no idea how it is getting through.
Water will get into any buried conduit, especially if the ends surface in different areas (indoors/outdoors, 2 different buildings, 2 different floors of the same building, etc.)
Air flow through the conduit will carry atmospheric moisture into it. When the temperature underground is less than above, that can cause the moisture to condense. The same thing can happen with buried cable that has voids inside the jacket. This is why direct-bury CAT5 and phone cable is flooded with a gel, and why DB romex has a solid jacket, while regular romex has air space in it.
Sealing the conduit at each end will minimize water accumulation, the tighter the better.
I fought water accumulation in conduits and cables for a long time years ago before I understood the principles involved. I first learned of this with submersible pressure transmitters in water tanks. The rise and fall of the water and resulting pressure on the cable jacket would pump air in and out of the exposed cable end. Over a period of months or a couple of years, the jacket would get enough water condensed in it to wick down to the electronics in the transmitter and destroy it.
Manufacturers now vent the transmitter cable jacket through a capillary tube connected to a desiccant tube or bellows to keep water vapor out.
Even for non-buried cables, junction boxes and hollow fiberglass antennas, diurnal pumping (the slight change in barometric pressure over 24 hours) plus weather related changes in BP, can pump humid air in and then a drop in temperature allow it to condense. Again, it can take a long time, but I've had sealed J boxes get wet inside. Now I drill a small vent hole to keep that from happening, and most antennas come from the mfr vented.
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excellent advice for all of us, thanks SLOWeather!