Humidity tuning

air
rain
humidity

#1

Must be a very slow learner. Mine has been out there for several days and has remained stuck at 99% humidity the whole time, running some 30% higher than neighboring stations.


Humidity seems off
CL for Humidity explained
Humidity measurment failure
#2

Hi @unkajim. Welcome to the family. As of 8 Jan, our CL system has only collected three days of data since you set up your new station. We are tracking 5 different data sources in your immediate area. Once the data set corroborates and produces a valid baseline humidity reference value…the calibration will be automatically applied to your station. - the WF team


#3

Thanks. Good to know. Wonder if one of the tracked sources is my 1-Wire humidity sensor, located two feet to the south of the Air.


#4

Just measured via my Assman psychrometer (the good old one), I get a reading of 78° when my Airs show 81°. Think it is pretty ok, as the Airs are in a stevenson screen and I measure just outside them. Added the standard deviations of the Airs and my eyes :wink:


#5

Mine’s still stuck on 99%. If I could get at it via some interface, I would give it a negative 25 offset which would get it in the ballpark.


#6

Hello @unkajim . Appreciate the heads up. Took a peek at the CL comparison data for humidity for your station and the reference values have not been in agreement. Will have our humans take a look.

FYI – calibration is not as simple as a fixed value or % offset. Rather, we look at the spectrum of comparison humidity values to determine linear slope and offset. For example, your sensor might need to be tuned down xx% at the top end of the humidity spectrum, might be perfect in the mid-range, but under-reporting yy% in the lowest range. (This is very common with humidity sensors.)


#7

@WFstaff-One ongoing issue I’ve had is with my Air’s humidity readings lagging actual changes. Today we had a rain storm and although humidity in my area was 98% or a bit higher at most reporting stations, including my own Davis VP2, my Air reported a peak of only 94%. However the more significant issue is that now that the storm has passed, humidity has dropped to the 74-79% in my area (79% on my VP2) and my Air is still stuck at 91%, falling only 3% since 12pm. I’m not sure why this long lag exists or if this is something the CL system can or will detect and adjust.


#8

Describe the area around the Air. Posting a photo would be even better.

How high above ground is the Air sitting? How close is the nearest plant life. Does the Air have good ventilation?


#9

Gary, my VP2 is actually fairly close to a bush (too dark to take a pix now, but I’ll get one tomorrow) and my Air is sitting on a table for now, quite a bit further from any plant life. Both the Air & VP2 are about at the same height, 12’ or so above ground level. The Air has excellent ventilation in all directions.

Here are 2 pix of the humidity/DP plots. The VP2 plot is from WU and doesn’t give humidity directly, but does give temp & DP. My Air is still sitting at 91%, unchanged.


#10

Ah. What is the table top made of and is the table top wet?


#11

Gary, that might be a good call. Table is metal. I just went out to take a pix with the iPhone flash. There is definitely dampness on the table, but the Air is raised a bit off the table. Do you think that’s enough moisture to impact the slow drying? I’ve also included a shot of my VP2.


#12

From my experience it does not take much moisture to raise the humidity. Move it to a dry area and see it if changes.


#13

Gary, if you look closely you can see that there is still quite a bit of moisture on the Air itself. So I wonder if even if the table were totally dry, how much would the Air be impacted by the moisture on the unit itself?


#14

Move the Air but don’t dry it off. See if it changes.


#15

I’ll give it a shot. I actually dried off the table after having shot this picture. :slight_smile:


#16

OK, moved it to a dry ladder I just put out on the deck. Thanks for the idea, we’ll see what impact this has. But I still wonder about all the moisture still on the Air’s casing.


#17

Once in a dryer area the rain on the Air will evaporate quicker and the humidity should drop.


#18

Gary, thanks, I’ll let you know in the morning how this progressed. I’ve ordered a passive radiation shelter for the Air as I’ll probably have an issue for total shade as the seasons change. Do you know what impact a shelter has on the Air’s ability for lightning detection?


#19

I don’t personally know but others have had little to no issues.


#20

none as long it isn’t full metal and grounded.
Mine are in a wooden Stevenson shelter and detect normal