Author Topic: Solar sensors  (Read 2126 times)

WCDev

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Solar sensors
« on: May 29, 2012, 05:02:58 PM »
Hello folks,
Over the weekend I noticed my solar readings seemed to be a little low for the time of year - a quick inspection revealed the sensor looked clean, but thought I'd give it a clean anyway.

2 minutes later, a little distilled water and cloth and hey presto - another 100W/m^2! My reading instantly jumped from 700 to 800.

If you haven't cleaned your solar/UV sensor(s) recently, it might well be worth a quick clean!

Cheers,
Stu.

elagache

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According to Davis . . . . (Re: Solar sensors)
« Reply #1 on: May 29, 2012, 09:45:47 PM »
Howdy Stu and WeatherCat Davis station users,

I didn't think my solar sensor was particularly dirty, but for giggles I took a look at the Davis documentation for their maintenance recommendations.  According to the UV and Solar Radiation Sensors manual, they recommend cleaning with ethyl alcohol (not rubbing alcohol.)  At least in the United States, most rubbing alcohols are Isopropyl alcohol which perhaps would damage the sensor.  However, that leaves the problem of locating an alternative source for ethyl alcohol.  Of course, Wikipedia notes that:

Quote
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a solvent, and as a fuel. In common usage, it is often referred to simply as alcohol or spirits.

So after you've gone too all this trouble to try to clean your pesky Solar Sensor, perhaps you'll need to bit of ethyl alcohol of this other variety - to calm your flustered nerves!!  [beer]

Who'd have thought that owning a personal weather station could be this complicated!!  [biggrin]

Cheers, Edouard  [cheers1]

P.S. After all this research, yes I did clean the sensor, but it looked reasonably clean before hand.  No significant change in output.

WCDev

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Re: Solar sensors
« Reply #2 on: May 29, 2012, 10:20:40 PM »
So maybe I can get a few more watts out of it then  :)  I've always been wary of alcohol and plastic type materials, preferring distilled water whenever it'll do the job (which it seemed to do in this case), but the next time I'm near the chemists I'll pop in and pick some up.

One of the issues we experience here is a green/black moss/algae growth that covers everything (damp, west coast of Scotland) - I suspect this was my problem and the water was sufficient to shift it. I also seem to remember the solar/UV sensors lose sensitivity over their life - I need to check that out as mine is just going into it's fourth year now - that might also be having an affect.

Cheers,
Stu.

elagache

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With help like this!!. . . . (Re: Solar sensors)
« Reply #3 on: May 30, 2012, 12:54:37 AM »
Howdy Stu and WeatherCat fans,

So maybe I can get a few more watts out of it then  :)

depends on the proof!! [lol2]

I've always been wary of alcohol and plastic type materials, preferring distilled water whenever it'll do the job (which it seemed to do in this case), but the next time I'm near the chemists I'll pop in and pick some up.

To be honest, I was wondering about one of these new wetting agents like Simple Green and a host of similar products.  However, I was a little worried by the Davis instructions.  Sometimes water can get into a place it isn't supposed to if you undermine petroleum seals.

I also seem to remember the solar/UV sensors lose sensitivity over their life - I need to check that out as mine is just going into it's fourth year now - that might also be having an affect.

According to the Davis manual:

Quote
Here at Davis Instruments we have seen an approximate 2% drift per year on readings from these sensors.  For applications demanding higher accuracy, the sensors should be calibrated every year.

Oddly, the documentation doesn't mention how to calibrate your wallet to pay for the recalibration or what Davis will do with the money they gain from such purely scientific advice!  [biggrin]

Cheers, Edouard  [cheers1]

WCDev

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Re: With help like this!!. . . . (Re: Solar sensors)
« Reply #4 on: May 30, 2012, 05:10:25 PM »

Oddly, the documentation doesn't mention how to calibrate your wallet to pay for the recalibration or what Davis will do with the money they gain from such purely scientific advice!  [biggrin]

Cheers, Edouard  [cheers1]

Lol!

It would be good to know how it does drift - calibration is on the todo list and I'd like to be able to compensate for it with for example a simple multiplier if it's a straight linear degradation. I'll see if I can find out.

Cheers,
Stu.