Dewpoint reading too high (01036M)

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  • Updated 5 days ago
Starting around August 1st, it looks like my sensor is reading dewpoints way too high. We have had a lot of rain in Northern Virginia over the past month, but clear sky days with temps in the 90s and a dew point around the low to mid 80s is a little off. I looked back at the data and it seems this started around August 1st.

Did the usual, take down the station, open it up and cleaned around the sensor (there were a few webs), but upon returning it to the mount and waiting 30 min or so, all I got was an erroneous rain reading and still high dewpoints.

I checked other stations in the area and my dewpoints are running at least 6-10 degrees above them. However, my high temps and real time temps seem to check out. Also have confirmed that my solar powered fan IS running...

Not really sure what is causing this and no threads seem to address a similar issue - so I am reaching out to the community to see if anyone has any ideas?!

Here is a link to my station: https://www.wunderground.com/personal-weather-station/dashboard?ID=KVAARLIN134#history
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rpbarnhi

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Posted 7 days ago

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George D. Nincehelser

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Dew point is a calculated value from the temperature and relative humidity readings.

In the 5n1, both temp and relative humidity are read by a Sensirion SHT21 chip.

If your temperature readings are fine, the likely cause of a high dewpoint is a high relative humidity reading.

The SHT21 has a small window on it from where the readings are taken (see enlarged picture below).  The membrane in this window can easily be "contaminated" by a stray drop of water or condensation causing high readings.  Typically if it is just water contamination, it will dry out after a few days and relative humidity readings will return to normal.  However, sometimes the damage is permanent, particularly if the water carried other chemical contaminants into the membrane with it.  



If the relative humidity readings do not return to normal values after a good period of dryness (say, a week or so), you can replace the temp/humidity module with a $10 part from Acurite.   Acurite only supports replacement if you have a "socketed" module of the newer units, but some older units (from about 2012 and later) can use the same module with the soldering of 4 wires.

https://www.acurite.com/temperature-and-humidity-sensor-replacement-for-5-in-1-weather-sensors.html
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rpbarnhi

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Thanks! When I have time this weekend I will investigate further and take the action you listed here if needed. Appreciate the help!