I just installed the UV sensor for my WMR200 and it seems to be working. However now that the sun went down and the UV reading is 0 it now reports “Overcast and gloomy/Clear”. It’s actually still sunny out (even though the sun is going down…there is still light) although it is clear so that’s right.
My question is did I miss something so when the sun starts to go down it doesn’t show overcast and gloomy? Looking outside it’s not either of those. In fact I got clear skys and it’s just the sun is now starting to go down…
I am in a similar position and there are a number of recent discussions in the forum that will proably answer your questions.
I live in the tropics (17oS) and my WMR200 UV sensor doesn’t read above 0 for about 2 hours after sunrise and before sunset. Between these times it does not seem too bad. Further away from the equator i could see this problem being worse.
The icons shown in WD will depend on your current solar settings.
WD uses a relatively complex process to estimate whether it is sunny using a simple UV sensor data. Others appear to spent a lot of time modifying the WD settings to get a reasonable correlation with actual conditions. To date I have adopted an adjustment factor of 150% and reduced the % value for sunny down to 70%. Still needs a lot more work though.
I also bought a UVN800 together with my WMRS-200 station. It works fine (at this moment the reading is 3.0 UV, which is also the maximum expected for today, calculated by the weather institute). H
owever, WD calculates that for give longtitude and latitude the maximum solar radiation could be 800 watts/m2, while it also changes 3.0UV to 300 watts/m2. This means that I will get 0 sunshine hours, if I don’t tweak anything.
I don’t want to tweak the adjustmentfactor, as it will also tweak the output data towards my website (and >300 watts/m2 just isn’t true) so I indeed adjusted the Sunny value towards only 30%. In the last week my sunshine hours were quite good (offcourse, I also don;t get readings before 10 am and after 5 pm, because the UVN800 isn’t that accurate).
But having changed the values for Sunny, I also had to change the rest. Which makes this rating quite useless for the icons. I therefore download METAR readings from the nearest Airport (5 km’s) which are quite accurate.
I’m interested in how you guys solved these issues…
Wow, happy to know, I’m not the only person having this problem. The UV sensor helps a whole bunch but doesn’t help when the data is wrong.
Since my sunrise is at 6:42:54 AM; it’s now 9:30 AM and according to my website it’s “Overcast and Gloomy/Windy” with an UV index of 0. This is so wrong as it’s 100% sunny here but it’s definately windy so that’s right. I’m assuming the reason my UV sensor isn’t going up is because the sun isn’t over the sensor just yet increasing the value. Although I’d like to use WD data and not metar’s (except at night).
I’m kind of confused with the settings within Solar Sensor and not sure which one to look at first. Something tells me I need to change something in max solar time of day/time zone/lat/long, fudge offset but not sure what to change. I see the ‘Time of day shadow offset’ and that’s something I think might help but not sure exactly how or if that’s what I need. The percentages are nice but doesn’t help me when I’m at a reading of 0%. LOL So I know this isn’t the solution. It will once I start getting UV numbers but between 6:42 AM and 10 AM I just don’t see it changing.
Also, Jose where is this “Solarsensor” that measures global radiation? Do you think that’s what I need to change to get my station to give me a better information?
Jayman
Check what UV reading is on the console. If it is 0 on the console then there is not much WD can do to provide the correct result. Others have reported problems with the sensors or it may simply be that your location does not generate enough UV at this time of year. The following current discussion may be have the answers you are looking for.
The UV sensor appears to work at 10 AM when the sun peaks around the house next door. However between sunrise (6 AM) to then it doesnt’ register anything. There has to be some adjustment I can make to WD to get it to show the correct information. I just don’t buy the “not much WD can do to provide the correct results”. This is WD were talking about here…
I have had similar problems with My Irox. The fact is that a UV sensor is not adequate to measure solar radiation. The only way you will get sensible solar readings early and late in the day is to install a solar sensor. To this end I am currently putting together a solar in a jar sensor using a Irox temp sensor with a 3 meter lead/probe. Early experiments have proved that this will work. There are a number of threads in the forum covering this topic and are well worth the time to read.
jayman228, have you tried the ‘Time of day shadow offset’ to increase the solar reading before 10am? It is not infallible of course but at least you can set it to what the majority of your days before 10am are like.
Hi there,
I’ve been following this thread with interest, since I have been playing about with a WMR200 UV sensor for about a month or so. I’ve come to the conclusion that since the station is designed to show the UV Index - i.e. the level of harmful radiation, it can’t really provide a source for accurate measurement of sunshine hours or solar energy received - it is at best a guide. At my latitude (52N) a UVI of 1 is reached about 9.15 in the morning at present, and it falls back to zero about 15.30. It is starting earlier each day as the sun gets higher in the sky. I’ve tried angling the sensor towards the south and needless to say you get bigger readings earlier, but of course that is no longer a reliable UVI!
Currently I have the “sunny” threshold set at 18% and it still doesn’t record sensible hours of sunshine, so I’ve given up! As someone else said, I think the answer is a “proper” solar sensor rather than trying to make a UV Index sensor do the job. It’s a pity it doesn’t just measure the level of solar radiation and let WD calculate the UVI from that!
One thing which puzzles me is that when the UV goes from 0 to 1 in the morning, WD shows a solar reading of 28%. This then declines, reaching 13% at about 12.00. It then goes up again slowly in the afternoon, reaching a peak of 20% or so at the point the UVI goes back to zero. This curve is exactly the opposite to what I would have expected - can anyone explain it? I must be missing the point somewhere…?
Also, Jose where is this "Solarsensor" that measures global radiation? Do you think that's what I need to change to get my station to give me a better information?
Well, I bought a THGR810 Thermo/Hygro Sensor and modified it by using a lightsensor and two resistors. There’s an option in WD to use such a modification for the WMR200 as an real globalradiation measuring unit.
If you’re are interested in it I can show you a link or explain my modification in detail.
This curve is exactly the opposite to what I would have expected - can anyone explain it?
WD calculates the % solar based upon what it should be for that time of day for your specific lat and long location. The calculated total solar value increases in the morning till noon and then decreases in the afternoon. Therefore if the UV value does not change during the day then the % solar will decrease towards noon and then rise again.
For this to work the correct lat and long values need to be entered in the WD solar setup (watchout for how -ve values should be entered).
Just as a UV sensor can only give an estimate of solar, a solar sensor could only give an estimate of UVI, so you might not be a whole lot better off. If you really want both values, the solution is 2 sensors…
Ha! Thank you to FNQ, now I understand. This really doesn’t work too well with a solar value based on UVI and having no decimals - the difference between UV=1 and UV=2 must be something like 20% of the maximum solar for the UK. Hmm, I can feel a second sensor coming on!
I searched for this information and there exist a good webpage about that. Unfortunately written in German. Solar-Sensor
I got help from an member of a German weather forum.
Now, after the credits I’ll try to explain the modification.
First you need a light probe and a 2,5kOhm adjustment resistor and the THGR800 or 810. Other units are possible, too as you can see on the website mentioned above.
You have to open the measuring unit and remove the temperature bead. You replace it with the resistor and the light probe in a row. That’s all.
After that you have to setup WD. Therefore go to the settings – > solar sensor.
There you have to tick the option of solar sensor in
Hi Jose,
Many thanks for the info, there is no need to post an image as far as I’m concerned, I understand what’s needed perfectly. I’ve just ordered the T/H sensor and I think I’ll use a small piece of solar panel as the actual solar sensor, then I can use appropriate resistor values according to what voltage it produces. I’ll do some experiments with it and see what I can come up with.
Regards,
Joe.
Thank you. Clear enough via Babel Fish! I’m surprised that the sensor appears to be mounted at an angle rather than horizontal, but maybe I just got the wrong impression?
Currently I use a “temp in a jar” solar based on an OS THC238. I’m hoping to gradually move towards a 1-wire setup. When I get the cable laid (wireless has a lot to be said for it!) I hope to set up a 1-wire pyranometer sensor using a small PV cell (inspired by this topic).
I’ll try to explain the modification.