[wxqc] Vantage-Pro Dew Point Calibration Question

[Dave Helms]

Hi Charles,

Looking at your station's location in the side of a hill and 1-2 miles 
from the closest water, St Johns River, there does not appear to be any 
reason to justify an elevated dew point measurement.  Your station is 
running 1.5F to 3.5F higher than the ASOS in your area, Frenchville and 
others, according to the MADIS statistics.  If possible, its best to get 
a coincident measurement using a sling psychrometer or other portal 
temp/dewpoint sensor to know for sure that your station is running too 
moist (there are alway several for sale on Ebay, where I purchased 
mine).  If the sling confirms that you are indeed too moist, then I 
would suggest recalibrating the dew point in a way the results in a 1-2 
F drier value (don't try to make a big change when tweaking your values, 
always make changes with by modest and incremental amounts as it is easy 
to over shoot).  If you cannot independently validate the wet bias, best 
to leave things alone as you reports are reasonably close to the area 
measurements (3.5F bias is just barely out of tolerance).

Hope this helps,

Dave
CW0351

Charles Ames wrote:

> Hi All,
> On the QC for my weather station I get the following message:
>  
> There is a significant mean error in your dewpoint readings. You may 
> need to calibrate your dewpoint sensor. Adjust your sensor to read 3.5 
> °F lower. Your readings are not within an acceptable error range. The 
> automated problem analysis cannot identify the problem.
>  
> I am assuming [I hope correctly] I need to calibrate the offset on my 
> thermomter 3.5 degrees lower? Is this right? Any suggestions.
>  
> My weather station is the wireless "Vantage-Pro" and the Sensor Suite 
> is about 5 ft.above the ground and in the clear
>  
> Thanks Charles
> Grand Isle Maine AR198, N7GLR
>
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