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Weather Station Hardware => Ambient Weather and Ecowitt and other Fine Offset clones => Topic started by: Eno on December 22, 2015, 10:41:17 AM

Title: solar radiation sensor non-zero reading
Post by: Eno on December 22, 2015, 10:41:17 AM

At night, a WS-1001 solar radiation sensor had normally dropped to zero w/m² but last night read about 0.6 (1 on WU) and this morning before sunrise was reading 2.5 (3 on WU).

Drift?  Margin of error? Defective?

Thanks.

Title: Re: solar radiation sensor non-zero reading
Post by: gfmucci on December 22, 2015, 05:06:59 PM

Send Ed at Ambient an email (Google Ambient Weather).  He usually replies within a few hours.

Title: Re: solar radiation sensor non-zero reading
Post by: SLOweather on December 23, 2015, 02:03:36 AM

Likely firmware programming considerations. The key is that you just noticed it the last couple of nights. The 25th of December will be the full moon. Your sensor is reading moonlight. I have a Davis VP2 ISS with a custom SIM board replacement. That firmware doesn't clamp the solar reading either.

Right now (10:47 PM PST Tuesday, 22 Dec 2015), that station is reading 1 w/m^2 with clear skies and the moon at 96% per the Old Farmer's Almanac site. Similarly, I have about a 150 watt (theoretical) solar array. It's putting out 1.34 volts open circuit, and 0.0014 milliamps short circuit right now.

While the math isn't exact for the maximum power point, that's an approximate output of 0.001 watts under a 96% moon. The array is 4 x 4 feet, or 1.5 m^2. Allowing for the accuracy of the solar sensor at the low end, and the age of the panels and their efficiency (less than 10% no doubt), (2 are from the original Carizzo plains solar generating station from the 80s or so), I'd say that's pretty close.

Quote from: Eno on December 22, 2015, 10:41:17 AM

At night, a WS-1001 solar radiation sensor had normally dropped to zero w/m² but last night read about 0.6 (1 on WU) and this morning before sunrise was reading 2.5 (3 on WU).

Drift?  Margin of error? Defective?

Thanks.

Title: Re: solar radiation sensor non-zero reading
Post by: Rychu on December 26, 2015, 05:45:21 PM

Quote from: Eno on December 22, 2015, 10:41:17 AM

At night, a WS-1001 solar radiation sensor had normally dropped to zero w/m² but last night read about 0.6 (1 on WU) and this morning before sunrise was reading 2.5 (3 on WU).Drift?  Margin of error? Defective?(...)

I have the same intermittent problem (in Poland) with the HP 1001 ---> maple WS1001 - but I think the fault of the scattered light of the street ...