Hello all. I joined the forums today to try and get some help on an issue I am having. I have used the forums for reference in the past but just as a reader. I am an average joe who has always been interested in weather. I have a VP2 that I've been running for just over 2 years now at my house. Lately however I've noticed an issue with my humidity readings. Ill lay that out here to see what some others think.
My humidity seems to always be reading a little low (10-20% low) compared to all the other weather stations around me. The inaccuracy seems to be greatest when the humidity is really high. I live in Florida so we have a lot of high humidity often. I started to really notice the issue when wunderground began not showing my station on the wundermap, and I was losing my little badge that signifies a good station with accurate uniform readings for like 5 days I think it is. During the day, like right now at 2:20pm my humidity is reading about 10-15% below everyone else, but I am dead on what weather channel and weather bug, and other "official sources" are saying, which tend to go off of the readings from a small regional airport about 20 miles north of me. So I wonder if I'm accurate and everyone else is wrong, or what the truth is here. I am below EVERY weather station on the wundermap within a 100 mile radius - several of which are other Davis units. Also of note is my Humidity seems to hit a ceiling and it wont go above it, which for all of February so far is 85%. Even in the middle of heavy rains, and at night, it will just stop at 85%. If I look back over the past 2 years and just look month by month at the highest recorded humidity level, it shows a pattern of steady decline of this maximum figure, as if the maximum it will register has steadily fallen starting just a few months after I installed my VP2. Just 1% or so drop off each month, but it is a steady decline to the current time. Its really weird. Yesterday I took my whole unit apart and cleaned it - removed the sensor and the little screen housing around it and cleaned it all, put it all back together. I thought perhaps the steady decline suggested something affecting the sensor - dirt, spider web, something. Cleaning it however has yielded no change. Today I ordered a new sensor and will install it and see what happens.
Many times I am much closer to the "official" humidity then other stations around me as reported by the local air port, but some of the units I am seeing on wundermap are good units, some of them run by big farming outfits and folks like Duke Energy, who I would put weight into their units and installation and therefore their accuracy. Is this just a case of a bad sensor? There just seems to be no consistency with how innacurate it is. Sometimes Its close enough it doesnt stand out, other times it looks like a real odd ball on the map, and many times it matches what official sources report while surround wunderstations are a good bit off from where me and the airport are reporting. I'm also curious about the very clear and uniform pattern of max humidity reading decline over the past 2 years. When I first installed the unit I had days where Id hit 100% humidity. Then about 3 months later max for the month was 99, then 97 a few months later, so and and so forth and now 85% is the max. In january I recorded 86% max. Not a single month in the 2 years deviates from this decline. Would love to get others thoughts on this.
EDIT: also for the record my Temperature is dead on the money with everyone else. No issue with temp at all