[wxqc] Humidity Jumps Normal?

Mark Wyman mark at markwyman.com
Mon Dec 15 08:45:17 CST 2008

To me, based on it slopes and is not a square or sudden sample to sample drastic edge indicates the sensor is really reading what it sees. It is likely moisture trapped in vegetation that occasionally drifts to your system by light breezes before being mixed with surrounding air. A micro-climate. I think you will especially see these when you don’t have much wind, the water nearby is warm, and the surrounding air is cool.


I get humidity spikes of a different sort this time of year when my system which is on a hill pokes it’s head into warm wind advection where almost all stations below my elevation are stuck in the cold, still air. Occasionally wind will mix down the warm, moist air above, and I will get a spike, before cold air settles around the station again cutting it off. Interesting phenomenon for sure.


The tough part for me right now it seems many of my surrounding stations have not calibrated their air pressure well, as my three meters are calibrated to elevation and to the airport metering, I am given two bad checks locally since the surrounding stations did not go through the effort to be that precise. What worries me is all surrounding stations read higher than mine… do I trust their average or do I trust my calibration? It may be time to re-calibrate for me.



From: wxqc-bounces at lists.gladstonefamily.net [mailto:wxqc-bounces at lists.gladstonefamily.net] On Behalf Of Derek McIntyre N4DBM
Sent: Wednesday, December 10, 2008 8:45 PM
To: wxqc at lists.gladstonefamily.net
Subject: [wxqc] Humidity Jumps Normal?


Hello Group,
I have been fighting with my humidity sensor for a while now.  I kept it off line for several days in a room with fourteen - yes, 14 certified hygrometers used in the agricultural field, all reading withing 0.5 % of each other, and calibrated my humidity sensor with these hygrometers (my original humidity calibration was only 1.2% high on average).  I thought I had a problem because I kept getting readings at random like in the picture attached.  My station (blue) had jumped up and back down very quickly while the average (red) stays fairly smooth.  Is this in any way a possible weather phenomenon or does it look like a sensor problem?  I have repeatedly tested all cables, voltages on the sensor, everything you can imagine.  Take a look at my attached pic - any comments or answers welcome.

Derek AS593 N4DBM-2

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