Plummetting humidity while raining

Paragon · Post by **Paragon** » Wed 03 Jul 2013 8:50 pm

Hello,
My Vantage Vue is telling me that the outside humidity is 32% while it is raining. The humidity began falling when it started raining last night. The upshot is that Cumulus has told me of a new record: lowest dew point, -4.2 deg. C. I don't believe it!

Does anyone have any similar experience? I am about to start troubleshooting by looking at the Davis web site.

Thanks for your thoughts.

Touchtone · Post by **Touchtone** » Wed 03 Jul 2013 10:49 pm

The dew point is always below the actual air temperature, in other words the temp cannot fall below the dew point. So if it was very cold when you saw that reading it may be correct. The humidity can vary even when it is raining & again is dependent on the air temp, but a low humidity reading while it's raining does seem unusual.

beteljuice · Post by **beteljuice** » Wed 03 Jul 2013 11:38 pm

The humidity began falling when it started raining last night.

You mean your sensors / circuitry got wet

Paragon · Post by **Paragon** » Thu 04 Jul 2013 1:14 am

beteljuice wrote:
You mean your sensors / circuitry got wet

Hmm. I wonder how. It was calm and the rain rate was low. I have not seen it do this before and we have had big downpours as well as downpours in strong winds since the station went up. Condensation maybe?

Where is the sensor in the unit?

Paragon · Post by **Paragon** » Sun 07 Jul 2013 4:14 am

I have just taken the outdoor station to pieces. There may be moisture inside the circuitry although I didn't look in there. There were spiders and their webs everywhere plus a lot of dust and spider droppings. It is clean now and back in service with a spray of surface insect killer. The readings now look better. If it does it again, I'll have to look inside the circuitry. In the meantime, I'll buy a tube of insulating and water excluding grease for the circuit boards, just in case.

Thanks for looking and thanks beteljuice for your response.

Graham

Paragon · Post by **Paragon** » Mon 08 Jul 2013 9:52 pm

Final observation: humidity has been drifting down since early May => sensor drift or failure.

Edit:
By the way, when I attempt to "Select a Graph" outside pressure from 1 May to today, the graph hesitates then disappears. When I click "Select a Graph" again, it comes back, complete. It doesn't do this for shorter time periods of graph.

Paragon · Post by **Paragon** » Thu 01 Aug 2013 3:49 am

Problem caused by sensor failure. New sensor -> more sensible humidity reading. Xclnt.

beteljuice · Post by **beteljuice** » Thu 01 Aug 2013 3:58 am

Sorry about being right, or were you covered by warranty ?

Paragon · Post by **Paragon** » Thu 01 Aug 2013 4:59 am

The NZ agent for Davis sent me the sensor and I installed it. The circuitry is encased in a rubbery substance. The "rubber" on the new one is see-through while the original was black.

Actually he sent it to me for nothing because I have been trying to get some action for a month and they were on leave.

My unit is 3.3 years old so probably out of warranty?

beteljuice · Post by **beteljuice** » Thu 01 Aug 2013 5:05 am

Paragon wrote:My unit is 3.3 years old so probably out of warranty?

Lucky result then

Paragon · Post by **Paragon** » Thu 01 Aug 2013 5:26 am

beteljuice wrote:Lucky result then

I hope so. It is taking a while to come up to what I expect it to say. Currently humidity is 94% and it has just rained - everything is wet. While raining the humidity was 92%, rising from about 87% after installation and refitting station on pole. So hopefully in the next hour or so it will come to equilibrium.

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