Topic: Humidity readings far lower than other local PWS-1001 wifi unit

[andrelanglinais]

I am noticing my weather station is giving humidity readings that are far lower than other local PWS in my area.  Anyone else have problems with this on these weather stations?  Any suggestions?

[StratosDog]

I looked at our humidity value compared to others on the Wundermap. Our temperature is within a degree of most of the other nearby stations (regardless of brand).

When we switched to display dew point/humidity we were surprised that our WS-1001 shows 15 percent less dew point and 30 percent less humidity. Right now reports 49 percent humidity while the nearby stations shows anywhere from 75 to 83 percent.

I also have another electronic device showing 53 percent. It is actually quite pleasant out now so I am going to be heretic here and say that our value is believable.

I am not sure if this type of local variation is possible. One solution would be to get a Sling Psychrometer and then calibrate the unit. These can be expensive.

I'd welcome suggestions from more experienced Weatherists.

[andrelanglinais]

I contacted Ambient Weather.  After they reviewed my data over the past two months, along with data from other stations near mine, they agreed that I have an issue.  I noticed over a month ago is when my humidity and dew point readings seemed rather low for south Louisiana.  I continued to watch the readings and compared to other stations that were within 10 miles of mine.  Mine was way off.  They are replacing my sensor array at no charge.  I'll be able to compare the new vs. the old once I have the new one up and running here in a few days.

[andrelanglinais]

I'll add that 10% humidity on an August day in coastal south Louisiana is not valid! LOL And, not when the airport 5 miles away is at + or - 80%, along with every other station around here.  Temperature is accurate, along with barometric pressure.  I do notice, however, at night the dew point and humidity readings seem to be accurate.  Only from about 0700 to around 2000 to 2100 do they start to go back up and are near or the same as other local PWS.  Like I said, I'll see what happens when I set up the new sensor array, but even Ambient Weather thinks I have a problem with the current system.

[Old Tele man]

Did you see this earlier posting?

http://www.wxforum.net/index.php?topic=22767.msg219291#msg219291

[andrelanglinais]

I hadn't noticed that one, thanks!

[StratosDog]

According the formula my station sensor is way off. Similarly my other outdoor humidity unit is also way off and just happens to correlate within 5 percent of the station sensor.

I will have to report this to Ambient.

[StratosDog]

After talking to Ambient Weather they said to adjust it by calibration. I bought a Sling Psychrometer and measured that way.

When the humidity is in the higher range, the unit's reading is low by 30 percent. But when it is moderate the humidity reading is only low by 15 percent.

I adjusted the humidity to increase it by 30. Now on this mild afternoon my unit shows a value 20 percent higher than neighboring stations. So instead I am going to adjust it to only 15 percent higher (this is still a bit higher regionally).

Calibration ability is great but the problem is we can't adjust the whole curve. On a unit like this it probably can't be made to be that complex.

[miles267]

I've noticed that my Ambient Weather WS-1400 is reporting Outdoor Humidity of 95% whereas my local airport weather station is reporting humidity of 85%.  -10% lower than me and it's less than 5 miles away.

Should I calibrate my ObserverIP at -10% so that they match or can humidity this much?

[SpringHillWeather]

Curious, those with humidity variances where is your station mounted, up high?

[bluenadas]

I have a 2 year old WS-1000-WIFI, which is essentially a first-run unit. Looking at my relative humidity & dew point values as compared to those around me it is VERY low. I live in Houston and right now, at 9am humidity is about 80%. But mine reads 39%. And if I look at Wunder Map, nearly every PWS that is reading incorrectly is a Ambient Weather unit. Why is that?

Well, I called them and brought up this issue. Come to find out they have a known issue with their earlier sensors where the humidity readings drift. They have corrected this issue in their newer units. Also of note, is the fact that the sensor array is the same for most of their weather station products. (1000, 1001, 1200, 1400). Given my unit is quite old I am obviously not under warranty, but I was told that a complete sensor array can be purchased which includes the updated equipment to avoid the bad humidity/dew point readings.

For anyone interested, search for WS-1000-ARRAY on their website and you can replace your sensor array for about $120 after shipping is added in (array itself is ~$103). Not the answer I was hoping for, but it is a fix for my issues.