Outside Relative Humidity on WH1080

[timfy]

Hi all,

Apologies if this post belongs somewhere else, but as anyone in this part of the forum probably owns a WH1080 or one of its many derivitives, I figured it was as good a place as any

My station appears to read low when RH approaches 90%-100%

For example, when local RH as measured on several other local stations is around 70%-80%, my station tracks them pretty much bang on. However when, like today, the nearest stations are all reading 95% - 98%, mine consistently reads about 10% low.

A quick check on Wunderground shows the following:
Mine
83%
Other local stations
95%
99%
98%
96%

I have no correction factors set, and cannot really see how any could be applied without throwing the results out at lower humidities.

Alright, enough waffle! Has anyone else noticed this on their stations, or better still have any ideas how this can be corrected?

Cheers all.

PS
Steve, I am loving the cumulus software, probably the most stable code on my PC, OS included!!!

[Frank02]

Hello timfy,

I thought I was the only one having that problem here. I have exactly the same problem as you and as in your case, I can't apply a calibration factor as this would not work for lower humidity figures as they are usually pretty close. It's only in higher humidity situations that don't work.

My station has never reported a humidity higher than 85% even though it should have went up to 98-100% many times. I am not sure of what is causing that but I heard of others on a French site that also had a similar problem and what they did is drill 'holes' in the sensor casing which seem to have improve things a lot for them.

I am not ready myself to do that. I don't own a fine offset + a vantage pro station like the people who did this. And one has to be very careful not to break any inside parts when drilling the hole(s).

[taddeus]

Hi All,
first ... many thanks to Steve, Cumulus is simply a great software.

I've the same problem with this weather station, about 10% of difference with other stations near me.

Frank, can you write here the link to that French site? I don't know where I've to drill the hole.

Sorry for my bad english and best regards.

Stefano

[Jonsey]

I did the drilling hole bit this weekend, it seems to have improved the humidity reading, it is now only about 2-3% out on weather reports for my area,

The case is super-glued together, I had to start the seperation process at the bottom where the sensor mounts onto the bracket, it is hard to do but it will come off, just be careful not to snap the housing in to two pieces, I gradually moved a flat headed screwdriver up the join line separating the unit. In total I drilled about 10 holes 1mm in diameter, 5 (in the shape of the number 5 found on a dice) on the back part, with 2 below the vents, then 3 in a line on the front part at the top portion above the vents already there.




Dave

Update- well it was only 2-3% out, now its 5-6% at the moment.

[taddeus]

Thank you Dave

[Jonsey]

Thank you Dave

Happy to help Stefano

[timfy]

Great stuff Jonesy... keep us posted on the accuracy front. If it closes the accuracy down to 3% or so I will be climbing the ladder and replicating your modifications. If it still runs out to >10% then I'm temtpted to investigate removing the humidity sensor and sticking it on it's own PCB mounted in a virtually open container (just a rainguard)

[Jonsey]

Hi timfy

I have just been doing a random check on humidity for the area I live in, in total I have checked 4 weather websites against my own site and the below is what is recorded @ 1810 20/01

My current reading is 77%

bbc.co.uk/weather states 73%
freemeteo.com states 77%
uk.weather.com states 81%
accuweather.com states 75%

So looking at it, it's 4% out and is accurate against freemeteo.com

I also think it depens on how often the weather websites update there data. Mine is updated every 5mins. So there prob will be a time when you check, where it could be 6-7% out

Also I think what will help is, I changed the radiation screen that came with mine.
see here --> https://cumulus.hosiene.co.uk/viewtopic.php?p=5031#p5031
Dave

[harrym1byt]

Mine is currently steady at 71%. My nearest official station about 3 miles away shows 70%. The highest recorded level was 90% in September.

[Frank02]

Frank, can you write here the link to that French site? I don't know where I've to drill the hole.

Stefano

Hello Stefano,

I don't know if you can read French but here is the link: http://forums.infoclimat.fr/index.php?s ... =0&start=0

You can read on page 4 that people have drilled holes in order to "re-align" the humidity. Not with the nice pictures and explanations provided by our friend Dave here. I am very tempted to do the same and see if it helps.

Although I am quite in line at medium / low humidity values, I don't find it normal that I never got a humidity reading over 85% as we had many very rainy days where most surrounding weather reports showed humidity level of 98 to 100%.

Thanks.

[taddeus]

Many thanks also to Frank and the other.

In my area ( northern Italy, frequent fog, relatively frequent snow and ice in winter, last week -12°C..., intense heat in summer) is common to have a r.u. of more than 90% (my instrument read 89% max) so, the hygrometer, appears clearly not reliable.

Thanks to all and best regards


Stefano

[taddeus]

Modding done yesterday, already it seems that the measures have improved.
Have a nice day.

Stefano

[keithatrochdale]

Can you post a picture please?

[taddeus]

Can you post a picture please?

I've done exactly as Dave, see images in the previous page of this thread.

Enjoy with drill

[sdsi]

This is the fix!

http://w8681.blogspot.com/
http://www.flickr.com/photos/bn37ej/set ... 701058879/