[werk_ag]

I was concerned about the curvature of the dome however and how this might reflect / refract or even focus the sun light. Also, for the solar panel at least, would be very difficult to moiunt it directly under the dome with no air gap.

I'm almost sure that the curvature of the dome will cause problems. Another possible problem is making that enclosure resistant to weather elements (water, sun exposition, etc, etc.)

My preferred enclosure is like this one:






Unfortunately I never found one on ebay with a clear cover (without that white trace).

Those enclosures are very resistant, they are made to be installed in the ground. It's very easy to remove the switch at the back, and use the hole to pass the cable (just make small hole in the membrane, then after pass the cable seal it with silicone). There is plenty of space inside to install the solar / UV interface



Here is a picture of the unit I'm using since two years.



I bought mine at a local store. The cover is made of a 5mm glass, which has lowered the UV readings by around 30% (later compensated in the software, by comparing the readings with nearby weather stations, and values published on portuguese official meteo site). Not a very scientific method but enough to have readings inline with other sources.

[Palmyweather]

Looking at the photos attached above jogged my memory on something that my work can get a hold of without that white trace bar through the lens as well. I phoned one of the holders of this item and they confirmed that it was a glass face, but thought it potentially had a strengthining coat to protect the glass.

[attachment=561]

There's still a few in the country as a clearance line, wonder if that is a better option for me? Always up for making the project and my personal station a better, more accurate one.

[JT118]

I have a solar radiaometer atwork and will be testing this weekend ,(with and with out dome) assuming we get any sun, here in the West of Scotland! I only have a plastic dome. Also a sheet of 0.5mm PTFE. Shall report back. I have a Davis solar radiation sensor on my other station, (www.ayrshireweather.org )
to do other comparisons.

[werk_ag]

This only occurs on days where there is not a single cloud in the sky, or occurs when morning cloud burns off. You can see a significant drop during the middle of the day and a significant rise in the evening..

Returning to the described problem...

A after a more detailed look at the graphs, they suggest me that the PV cell may have a thermal problem. There isn't spikes or random readings, suddenly it just starts to give lower readings. This leads me to think that when the temperature rises, some internal connection in the PV cell fails, which makes that it provides less current, than is supposed to do.

As said by PM, a new PV cell is already flying to you.

[AllyCat]

Hi,

Strange, I thought I'd posted a reply yesterday, but it appears to have "vanished". However, I was only confirming that I'd be looking for a "mechanical" issue. Since the fall looks to be close to 50% it could well be one (of 2) or 2 (of 4) of the PV panel diodes becoming "short-circuit" due to overheating.

Regarding this matter, the following text in from the manufacturer of the UV sensor used in the UVM-30A module. ...

@ Werk_AG: Sorry, I din't notice your text and link before.

I'm certainly not disputing that the sensor is optimised for "Ultra-Violet", just that without a UVA-blocking filter, it cannot produce a genuine "UV-Index", which is very heavily biassed (by up to 3 orders of magnitude) towards passing (only) the UVB wavelengths.

I'm not sure of the OP's definition of "Cloudy all day", but the UV curve looks almost unchanged compared with the clear day!

Cheers, Alan.

[werk_ag]

Hi Alan

Strange, I thought I'd posted a reply yesterday, but it appears to have "vanished".

I never delete a post. I will try to check what happened.

I was only confirming that I'd be looking for a "mechanical" issue. Since the fall looks to be close to 50% it could well be one (of 2) or 2 (of 4) of the PV panel diodes becoming "short-circuit" due to overheating.

I think you are right. Seems an internal failure in some of diodes.

I'm certainly not disputing that the sensor is optimised for "Ultra-Violet", just that without a UVA-blocking filter, it cannot produce a genuine "UV-Index", which is very heavily biassed (by up to 3 orders of magnitude) towards passing (only) the UVB wavelengths.

I understand your point, and obviously I agree with you. Strictly talking, as defined, the UV index is related to UVB radiation only.

[werk_ag]

Hi Alan

Strange, I thought I'd posted a reply yesterday, but it appears to have "vanished".

I never delete a post. I will try to check what happened.

I was only confirming that I'd be looking for a "mechanical" issue. Since the fall looks to be close to 50% it could well be one (of 2) or 2 (of 4) of the PV panel diodes becoming "short-circuit" due to overheating.

I think you are right. Seems an internal failure in some of diodes.

I'm certainly not disputing that the sensor is optimised for "Ultra-Violet", just that without a UVA-blocking filter, it cannot produce a genuine "UV-Index", which is very heavily biassed (by up to 3 orders of magnitude) towards passing (only) the UVB wavelengths.

I understand your point, and obviously I agree with you. Strictly talking, as defined, the UV index is related to UVB radiation only.

Cheers, Werk_AG