Weather > Weather Hardware/Measurement
Troubleshooting resources for Davis weather stations
bcurry:
Hi all,
Thanks for the help.
I calibrated the sensor for external humidity, against an airport nearby (well, 9 miles away and a bit further inland - I'm right on the coast), and for a day it looked good. Then mine stayed higher than theirs and went to 100% and stayed there on a day it should have read maybe 65%. I took the calibration off - set back to 0 (i.e. as it was) - and have left it for two days and it seems quite OK.
It is supposed to rain this weekend quite hard, so we'll see what happens. It was the initial rain, pouring rain, and a reading of 50% that had me start all this.
If it is still wonky, I may try the cleaning trick.
Bill
bcurry:
Update-
Pouring rain here and my humidity is showing 45%.
Time to get a new one (I see Scaled Instruments is offering the new digital sensor for $45. - that seems reasonable!), and then see if the old one can be repaired or saved.
I looked it up and had had the station up at the end of 2010, and the old Hum sensor (and temp that time) went out in 2014. It's now 2017 and the Hum is obviously flaky.
I tried the calibration, and what I noticed was it was too high when dry - which makes sense because even now, yesterday it read 76% in dry conditions, but today in a downpour it's showing mid 40's...
Thanks for all the help,
Bill
xairbusdriver:
The 'cleaning' processes Mr. Crossley mentioned seem rather time consuming and possible difficult to accomplish at home. And you'd need yet another RH indicator. [lol]
I'm not sure you should expect to see very high RH values just because it is raining. Nor do I think a high rate of rain always results in a high RH. In fact, you would expect to see nearly 100% RH even without precip if you had heavy fog at the sensor.
While high RH is related to precip, the actual location of that very high RH is where the precip is forming; in the cloud. Heavy precip is often seen in thunderstorms and the temp on the ground can be considerably higher than even the base of the Cumulonimbus cloud. If the RH of the air below the cloud is low enough and the base of the cloud is quite high, it is possible that the rain will never even reach the ground (VIRGA).
While your sensor may indeed be inaccurate, I think you would need an identical or tested, calibrated sensor to compare it with. And, as far as I know (that's a huge variable!), RH can be a fairly localized measurement. I would think being close to a large body of water, especially with a shoreward wind, would have a higher RH than the opposite wind. OTOH, the RH in the middle of a large forrest will also have a higher RH than the same area covered by grasslands and certainly urban areas.
I do hope you find a way to verify the RH values in the least costly manner! ThU32:-)
mcrossley:
That's why I said I'd had good results just washing the sensor out and drying in centrally heated room for 24 hours. I don't have the facilities to do the documented recalibration process either.
You're right about rain, I have seen humidity as low as 85% or so when it is raining, though it is usually in the 90's here on the damp West coast of England.
elagache:
Dear Bill, Mark, and WeatherCat station caregivers,
--- Quote from: bcurry on May 06, 2017, 12:26:36 PM ---Pouring rain here and my humidity is showing 45%.
Time to get a new one (I see Scaled Instruments is offering the new digital sensor for $45. - that seems reasonable!), and then see if the old one can be repaired or saved.
--- End quote ---
Sorry you are having so much trouble with this sensor. You might try asking a question on the WXforum:
http://www.wxforum.net/
There are a lot of hard-core weather geeks on that forum and they might know something that would explain your problems with these sensors. I don't know of anyone else having similar problems, perhaps it has something to do with your station location or the weather conditions in your area.
Best of luck with this and do let us know what you discover so we can learn as well!
Cheers, Edouard [cheers1]
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