Solar Settings

[Flosex]

Thanks Alan. I have been waiting for some sunshine before replying to you!

The display is currently reading 25.2k lux and 37.0 W/m2 in reasonably clear sunshine.

Chris

[steve]

I think your sensor is faulty, assuming the sun is actually shining on it. But it's also odd that the console is apparently using a very low conversion factor.

[AllyCat]

Hi,

25k Lux is possibly "about right" since Wikipedia says "direct sun" is 25k - 100k Lux and we're still well short of mid-summer. But 37 W/m2 seems far too low (10x ?). Whilst I do generally like the 3080's LCD, the tiny "wandering" decimal point can rather easily be misread. Are you sure it's not 370 W/m2 ? I must admit that I've never tried the W/m2 format (maybe next week), but in any case, the FO software is certainly not completely "bug free".

Cheers, Alan.

[Flosex]

Thanks again, Alan. The display is definitely showing 37.0 W/m2, etc. I'm not misreading the decimal point - in fact the decimal point is very clear - perhaps they have improved the display since you bought yours, I bought mine last week?

I monitored the display this morning as the sun got brighter in a clear blue sky, and this is what I recorded as it approached and passed the 120 W/m2 'sunshine' threshold in Cumulus:

Time GMT Display lux Display W/m2 Cumulus W/m2 Display UV
******* ******** ********** *********** *******
0833 12494 18.3 98 1
0834 13182 19.3 104 1
0835 14970 21.9 118 1
0836 15228 22.3 120 1 SUNSHINE!
0837 15650 22.9 123 1
0838 15882 23.3 125 1
0839 16372 24.0 129 1
0855 18531 27.1 146 1
1025 23407 34.3 184 2
1126 39231 57.4 309.3 3
1134 42731 62.6 337.3 3
1149 47478 69.5 375 3

I then had to go out, but when I checked later, the highest W/m2 in Cumulus was 385 at 1247.

These figures suggest to me that the light sensor is reasonably accurate in measuring lux, bearing in mind we are only near the end of February and the sun is still low in the sky, but the conversion it uses to W/m2 is totally wrong. If I use the W/m2 figure computed by Cumulus from the lux readings of the sensor, then I think I will be about right. What do you think?

One thing that does surprise me is how bright the sun has to be before it reaches the 120 W/m2 'sunshine' threshold in Cumulus. Is this normal? The sun had been out for some time this morning before it reached 120 W/m2, and certainly what the 'man in the street' would call 'sunshine'.

I am very new to this hobby but am already finding it very time consuming, but also very interesting.

Chris

[steve]

One thing that does surprise me is how bright the sun has to be before it reaches the 120 W/m2 'sunshine' threshold in Cumulus. Is this normal? The sun had been out for some time this morning before it reached 120 W/m2, and certainly what the 'man in the street' would call 'sunshine'.

I'm not sure what this 'threshold' setting is that you've set to 120, or where you've got the 120 figure from. Where is it in Cumulus? The 'threshold' setting in Cumulus is a percentage.

[Flosex]

OK Steve, I thought 120 W/m2 was the world standard for 'sunshine', or have I misread something?

Chris

[steve]

That figure is the standard for direct radiation. Your sensor doesn't measure that, so you can't use that figure. That's why Cumulus has this complicated formula that calculates the current theoretical maximum global radiation which varies depending on the time of day, the day of the year, and your location. It then uses the current reading from your station compared to that theoretical maximum figure, to try to determine whether the sun is shining. There are three parameters that you can experiment with to try to make the calculation better. These parameters are described in the help; the default values are designed to get you close, but you will need to adjust them to get the best results.

[Flosex]

Thanks Steve, that's very helpful and explains my wondering about why the sun is shining quite brightly when Cumulus is showing less than 120W/m2.

I will look at the Help File and start playing with the three parameters you refer to.

Chris

[mcrossley]

I would think 120 W/m2 is way too low for bright sunshine, even for this time of the year, except for early morning/late afternoon. I may getting just shy of 500 (including cloud reflection which is significant with the low Sun angle). Take a look at my recent readings...

http://weather.wilmslowastro.com/highch ... Graphs.htm

Then click 'Solar'.

[Flosex]

The figures in my table were for early morning, Mark. The time (GMT) is shown in the first column. The peak for that day was 385 W/m2 at 1247 GMT.

The table below shows my Cumulus graph for the last four days and it isn't that far from yours, with high peaks of almost 400 W/m2 (three days) and 325 W/m2 on the other day. Does this suggest my solar sensor is working about right?

Chris

[steve]

That doesn't look too bad at all, so I think your sensor is OK and the console is just doing something silly with the conversion from Lux to W/m2 (which doesn't affect Cumulus as it does its own conversion).

Now you just need to play with the settings to try to get Cumulus to correctly show when the sun is shining. Bear in mind that the sensor reading doesn't update instantly.

[Flosex]

Thanks Steve, I will do that.

Chris

[AllyCat]

Hi,

I must admit that I've never tried the W/m2 format [on the Console]

OK, I've now been able to check the Console (it's at a remote location) and mine doesn't offer w/m2, only "Lux" and "Foot-Candles". Therefore FO must have updated the software, so I don't know what conversion factor they use for Lux to w/m2.

This morning's (noon) Lux reading peaked at 43k (fairly clear sky) which (at about 330 w/m2) is perhaps a little low. Certainly significantly lower than my previous Solar Pod (which "ate" batteries and was replaced as faulty).

BTW, have FO corrected the UV legend on the Console for UV Levels 5 - 6 (between "Moderate" and "High"), mine calls it "Extreme" ?

Cheers, Alan.

[Flosex]

Hi Alan

Yes the new software is obviously not making an accurate job of converting the lux readings to W/m2. I shall ignore them and rely on the Cumulus conversion figures, especially after tweaking the parameters as advised by Steve.

Re the WH3080 console, I don't know how your UV legend is designed, but mine is circular with 'Low' at the bottom (south), 'Moderate' on the right (east), 'Extreme' on top (north) and 'Very High' on the left (west) with the UV light number and arrow in the centre.

I don't know what corresponds to the various UV figures (there is no sun at present) but would imagine that 5-6 (being in the middle of the 1-10 range) will still indicate 'Extreme'.

Chris

[AllyCat]

Hi Chris,

No, I hadn't really expected FO to reprint their LCD screen (and User Manual). But, particularly as the UV "dial" is labelled anti-clockwise (?!), they could have modified the software so that the UV "Up-Pointer" is active for (say) UV > 9. But I wonder if FO even realise that they "got it wrong".

However, it's of academic interest to me as my UV sensor is now covered with PVC tape. It previously indicated about 4 digits too high (11+ in the UK !?) and was possibly responisble for the occasional (Solar Pod) software hang/crashes. Latest wisdom is that it is high Lux Levels which cause(d) the lockups, but I live in hope.

Cheers, Alan.