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Author Topic: 100% solar reading under completey cloudy sky.  (Read 1757 times)

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Offline broadstairs

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Re: 100% solar reading under completey cloudy sky.
« Reply #15 on: January 10, 2017, 03:20:46 PM »
That will be fine John, the only extra I need is the exact time the screenshot was taken. We may be able to progress a bit with what's happening. Can you also post a screenshot of the 'Max Solar Time of Day/Time Zone/Lat/Lon Fudge offset' tab on the solar control panel please.

Stuart

Offline John P

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Re: 100% solar reading under completely cloudy sky.
« Reply #16 on: January 10, 2017, 03:37:27 PM »
Here's that screenshot, Stuart.
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Offline John P

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Re: 100% solar reading under completey cloudy sky.
« Reply #17 on: January 10, 2017, 03:48:39 PM »
And here's the solar max.
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Offline broadstairs

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Re: 100% solar reading under completey cloudy sky.
« Reply #18 on: January 10, 2017, 05:23:42 PM »
Fine... that just leaves the Current Readings tab screenshot when it goes mad in the morning.

Stuart

Offline niko

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Re: 100% solar reading under completey cloudy sky.
« Reply #19 on: January 10, 2017, 06:08:57 PM »
Stuart: Is it possible there's a time zone or other problem here that's causing the calculated value to be out of sync? Isn't there a way to plot the calculated max on the graph with the actual?

Offline John P

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Re: 100% solar reading under completey cloudy sky.
« Reply #20 on: January 11, 2017, 08:34:48 AM »
Stuart, here are the two screenshots.................. time taken was seconds after it shot up to 100%.

Note the time on computer clock.

John
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Offline broadstairs

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Re: 100% solar reading under completey cloudy sky.
« Reply #21 on: January 11, 2017, 08:55:35 AM »
OK well as expected this falls into the category of YYGT (Yes You Get That)  :wink: Seriously though a reading of 5 and a max of 3 and you get greater than 100%. This happens to most folks whether or not they have the solar sensor shaded or not. The design of a Davis solar sensor is one which measures global solar not direct, that is it reads the whole sky including any reflections etc. This makes life difficult when you are estimating the sunshine as a % from actual w/mē values. Based on the values on those screen shots it seems likely that you need to stop WD setting sunny for a minimum of 30 minutes, my calculator suggests a reading of about 36 as expected max after around 30 minutes and you would need a actual reading of around 31 to show sunny with an 85% threshold.

As a slight aside to this I am puzzled by your lat/long values as they show up on a map as being some distance away from Daventry although not enough to make a significant difference to the expected max calculations. Daventry shows up on google maps as being about 52.2575N (52° 15' N) and 1.1649W (1° 9' W) although I realise you are probably not in the centre of Daventry your values put you north of the M6 near Churchover, which is correct?

Stuart

Edit. I just checked back and you have a sunny threshold of 70 which is way too low, it needs to be 80 at least and preferably 85 with the current way WD does this calculation. I have 85 sunny the 65 45 25 and lastly 15 as my values from sunny down.
« Last Edit: January 11, 2017, 08:58:58 AM by broadstairs »

Offline John P

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Re: 100% solar reading under completey cloudy sky.
« Reply #22 on: January 11, 2017, 09:27:40 AM »
Stuart, thank you for your time, trouble, and advice. I have followed your suggestions to the letter, using your suggested settings, and I have modified my lat/lon as per Google Earth.

Thanks again!

John
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Offline broadstairs

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Re: 100% solar reading under completey cloudy sky.
« Reply #23 on: January 11, 2017, 10:05:27 AM »
No problem. Don't forget to check the lat/long on the solar control panel as well.

Stuart

Offline John P

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Re: 100% solar reading under completey cloudy sky.
« Reply #24 on: January 11, 2017, 11:25:37 AM »
Wilco!!! :D
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