Solar sensor setup panel show 0 for max for this Lat/Long

I was wondering why my solar reading seems out and have just found that the max solar value for my lat/long (which is correctly set for here in the UK) is zero. Now does this alter as the day progresses? So at night time it will be 0, or should it permanently read the max daytime value for my lat/long and time of year? Once I understand this I can get a feel for whether my solar sensor is working OK or not.

its auto adjusted each minute (but you need to revisit that setup screen)
so, yes, its zero at night time, and will peak at solar noon
make sure you have the minute offset set as zero, and you do not have ticked use daylight saving

OK, so now I have taken a look at the control panel again nearly 1 hour after sunrise here in the UK and the reading for this lat/long is still 0. The actual reading is also 0 as at present it is overcast and drizzling, but I would have expected a non-zero setting for this value by now. I have daylight saving off and the minute offset zero.

Just taken another look and the sensor is showing a raw reading of 3, a percentage of 3% and the max value for this lat/long is still 0! I cant help feeling something here is wrong!

OK so I know I am thinking on the forum rather than thinking it through first! Anyway the max reading is now increasing, currently sitting at 25 with a raw of 4.2. I’ll now shut up until I have watched it through the day and see what happens. This all started because yesterday I got a 100% reading on a day which had been pretty much overcast all day! I guess I also need to take a look at my sensor!

I have another question here. I have had another spike of 100% this morning which I dont understand since it is cloudy and raining… If I check the w/m2 value in WD it shows 75, however I stopped WD and ran Weatherlink, downloaded the archive and checked the records for the same time period and it shows the solar radiation value as being between 5 and 7 for the same time period. So where did WD get 75 from or are we tallking chalk and cheese here? How can I view the actual raw data collected by WD to see the raw values for that period (rather than trying to read it off the graph)?

you can set to plot the raw wm/2 instead of the solar %…
but also you can see the raw wm/2 under view, solar real time graph

so, you dont have any minute offset set in the solar setup? (make sure that is set to zero)

with low wm/2 for the time of day for the time of year calculation…i.e for you in winter, at this time of the year, then the max reading in the morning might be say only 10 wm2, and so a raw reading of 5 wm2 will give a 50% solar %
i.e what I am saying is that the estimated solar % errors will increase as the max solar radiation level for the time of day and the lat/long are smaller and smaller… (i.e if your lat or long is not spot on, then wd might be underestimating your actual max solar reading for the part of the day when the sun first gets up…so that is where , though, you can apply the minute offset,…which effectively delay the solar noon by that amount,…so, actualy, try setting a , say, 30 minute offset in the solar setup

OK, I think I get the picture over % view, so lets ignore that right now.

Plotting w/m2 on the main window and expanding the scale shows that my raw reading jumped from 3 to 101, then fell back to 75 the fell graduall in jumps of 10 to 20 back down to 3.

Using View shows that over the same period the values appeared to vary between 3 and 4.5.

Using Weatherlink shows the one minute records having values between 5 and 7.

Now I hope you can see my confusion. Especially as the first thing I look at is the main window!

if you are using the bluewave sensor,(or even just try this ) it tends to over read in the winter
so use the solar adjust, bottom right hand coner, of the solar setup screen, to reduce the raw solar reading
that will help

off to bed now

Well somehow I dont think I have made my point here, lets ignore the accuracy of my sensor for now, yes it is a Bluewave MKII BTW. Also lets ignore the % values for now. Once I understand what I am seeing in the raw data I can move on.

What I am saying is that in WD the main graph on the main window is showing values which I cannot find in any other graph view in WD. It is showing a spike of 101 w/m2. In the View Solar graph the max showing for the same time period is 4.5 w/m2

Weatherlink roughly agrees with this showing a reading of between 5 and 7 w/m2 for the same period.

So why am I seeing these silly values on the main screen graph of w/m2?

not sure, it should be plotting the raw, direct, solar wm.2 from the davis VP
note though that if you were set to plot solar %, then it would have been stored as a solar % value, but if you now have solar wm2 plotted, well, WD does not know that it was once a solar % …get my drift?
but for a blue wave sensor, you will need to apply an offset… in winter espeicaly…I had to…(I have had one for 5 months now)

OK, I’ll leave it plotting w/m2 for now and see what happens.

What seemed strange is the sudden jump and we are not talking about a short time after sunsrise either we are talking about 0930 - 1000hrs GMT when sunrise is around 0754hrs GMT when it suddenly went from 3 w/m2 to 101.1w/m2 and then fell back slowly over about 1/2 an hour or so. All this time the raw values shown by Weatherlink and the view solar graph are around 5-7 w/m2. I dont see anyway that 5-7 w/m2 could be anywhere near 100% around 1.5 hours after sunrise even at this latitude. Is there any option to view a graph of the max solar value?

Here’s a calculator I found a while ago when I had similar questions

Don’t panic

100% means the solar was at the maximum for that time of day
thats easily attainable at 10am…and it should be that way…ie it should be attainable if you had clear skies…at that time…
but if the raw value is too high, which is likely with the bkue wave sensor, then the reading will be 100% even in cloudy weather
i think you are gettng confused with what the solar is %

Thanks for that… very useful

At 0930 the max value for my lat/long should be 226 according to the calculator web site.

So even if my 101.1w/m2 was correct it should have shown a % value of 44% not 100%, and with a w/m2 of 7 at 0930 GMT today it should have shown 3%.

So I’m sorry but I just don’t see how the WD graph is correct, neither by the way do I accept that a real value of 101.1 w/m2 was correct. There is no evidence I can find anywhere to say the VP passed a value of 101.1 to WD!. As I said I have been stopping WD and running Weatherlink to download the arcive, then browsing the records. All of the values in the 1 minute archives show a value of between 5 and 7 for the period when WD says I had a max value of 100% or 101.1 w/m2. I assume that the website posted by nikoshepherd has a valid calculator on it. Having input my lat of 51.21.48 N and 01.26.25 E it shows a max value of 226 for today at 0930hrs GMT risiing to 282 at 10.00hrs GMT.

because you had wd set to plot solar % before, but now you have it plotting solar wm/2, then 100wm/2 was a 100% reading record
i hope you understand

Yes I do understand what you are saying about the percentage values.

Now assuming that WD does not write the data back into the datalogger on the VP or otherwise corrupt it, and assuming the web site gives me a good approximation of the max solar reading in w/m2 for my location the following seems logical to me.

As I stop WD twice a day and run Weatherlink to archive all the data from the VP datalogger I should be able to get the w/m2 value from the relevant record in WLink and using the calculator on the web site found by nikoshepherd I should be able to verify the % plot buy WD or at least get very close to it. The website gave me a value of 226 w/m2 for the max solar rad at 09.30 rising to 282 at 10.00.

Now I cannot do that as WLink shows the value to be between 5 and 7 w/m2 all through the hour from 09.30 to 10.30, and using the max solar radiation from the web site calculator I should have had a value of 3% solar percentage showing on WD graph, but I did not I got 100%. So what I am saying is that either my PC cant add up or there was something wrong with either the data as WD saw it or something wrong with the calculations under the specific circumstances at 09.30.

Now I am quite happy to believe there is something strange going on here, but I don’t know how to get the raw records out of WD. Is there some way I can save the raw data for say a rolling period of time so that I can go back and have a look at the raw data WD got to compare with what WLink sees. That way I can start to get to the bottom of this. This is not the first time I have seen this problem, it happened a couple of days ago but I did not do anything at the time. Now seeing it for a second time it is a problem I want to solve.

I think it’s going to be hard to validate the % and the absolute reading in the same experiment. My suggestion would be to turn off the % calculation/graphing in WD for 2-3 whole days and validate that you are getting reasonable W/m2 values. Since you don’t have a Davis solar sensor and there seems to be some question about the calibration of the bluewave I think this is an essential first step. During this time you can also do the daily archive dump into WL (after sundown) and look at the data there too.