Author Topic: What else can cause a stray UV spike?  (Read 2297 times)

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Offline funsutton

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What else can cause a stray UV spike?
« on: June 09, 2020, 05:02:27 PM »
Since I own an ambient system, I thought I'd post this here.

I noticed last night that at 1:54 am I got a UV spike of 14 on my WU graph. It's not recorded in any of my other data, but that's not surprising since my WS-2000 console only logs one entry per minute and sends to AWnet only once every minute. I believe WU gets multiple updates per minute.

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To my knowledge we didn't have lightning last night, but not sure that lightning could cause a UV spike. The solar radiation was zero, by the way.

Is this just a glitch or did I pick up an alien space ship cruising through atmosphere?

Offline e91071f86d

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Re: What else can cause a stray UV spike?
« Reply #1 on: June 09, 2020, 06:26:31 PM »
I've also had this randomly happen before as well on my WS-2902B but haven't been able to identify a cause.

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Re: What else can cause a stray UV spike?
« Reply #2 on: June 09, 2020, 06:37:49 PM »
Fireworks
Meteorite
Flash cluster of fireflies
Idiot kid with a match.

I am getting punchy.



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Offline funsutton

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Re: What else can cause a stray UV spike?
« Reply #3 on: June 09, 2020, 08:55:10 PM »
Quote
Fireworks
Meteorite
Flash cluster of fireflies
Idiot kid with a match.

Ok. Thanks for the info.

Offline kenthcwx

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Re: What else can cause a stray UV spike?
« Reply #4 on: June 10, 2020, 11:42:32 AM »
Since I own an ambient system, I thought I'd post this here.

I noticed last night that at 1:54 am I got a UV spike of 14 on my WU graph. It's not recorded in any of my other data, but that's not surprising since my WS-2000 console only logs one entry per minute and sends to AWnet only once every minute. I believe WU gets multiple updates per minute.

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To my knowledge we didn't have lightning last night, but not sure that lightning could cause a UV spike. The solar radiation was zero, by the way.

Is this just a glitch or did I pick up an alien space ship cruising through atmosphere?

Has happened many times on my station before. It's just a glitch that everyone inevitably gets from the system. Doesn't seem to be a fix for it.
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Offline Mandrake

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Re: What else can cause a stray UV spike?
« Reply #5 on: June 10, 2020, 11:49:27 AM »
I think everyone has learned to live with it (spike wise and accuracy)
It has been asked of Ecowitt that they consider building a 'real' UV independent sensor
I don't think the integral sensor is really measuring UV but deriving it from Lux levels. (Might be wrong on that...anyone able to confirm or otherwise?)

I just treat it as a indicator rather than any degree of precision.
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Offline kenthcwx

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Re: What else can cause a stray UV spike?
« Reply #6 on: June 10, 2020, 11:54:47 AM »
I think everyone has learned to live with it (spike wise and accuracy)
It has been asked of Ecowitt that they consider building a 'real' UV independent sensor
I don't think the integral sensor is really measuring UV but deriving it from Lux levels. (Might be wrong on that...anyone able to confirm or otherwise?)

I just treat it as a indicator rather than any degree of precision.

Would make sense since my UV levels spike whenever the solar radiation spikes. I don't take any notice of the UV really. If they made a better sensor, then I would.
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Offline galfert

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Re: What else can cause a stray UV spike?
« Reply #7 on: June 10, 2020, 12:02:54 PM »
Fine Offset clones currently use Lux sensors only and then they asign conversion values to report UV and Solar Radiation. Not the most accurate method. But it is what currently enables the given price points.
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Offline funsutton

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Re: What else can cause a stray UV spike?
« Reply #8 on: June 10, 2020, 12:03:20 PM »
Quote
Has happened many times on my station before. It's just a glitch that everyone inevitably gets from the system. Doesn't seem to be a fix for it.

Glad to know others are getting it too. Means there probably isn't a good explanation for it, other than perhaps a lightning bug sitting on it...

Quote
I think everyone has learned to live with it (spike wise and accuracy)
It has been asked of Ecowitt that they consider building a 'real' UV independent sensor
I don't think the integral sensor is really measuring UV but deriving it from Lux levels. (Might be wrong on that...anyone able to confirm or otherwise?)

I just treat it as a indicator rather than any degree of precision.

I'd to think mine is somewhat accurate, whatever it's actually measuring. It does seem to match for the most part the UV that the forecast predicts. Although I've seen some Ambient UV sensors in my area hit 13 and 14 every day, even if the actual UV is around 7. If it ever starts doing that, it'll be useless.

Thanks for the input.

Offline galfert

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Re: What else can cause a stray UV spike?
« Reply #9 on: June 10, 2020, 12:06:57 PM »
One noted cause for spikes is condensation drops on the sensor that then acts as a lens thereby throwing off the Lux sensor. I notice it in early mornings if the conditions are right as the sun comes up. I can see a full moon doing this spike with condensation drops. Maybe your sprinkler system ran at that time or there was a light rain.

Rainfall during the middle of the day is usually not an issue because it evaporates quickly and no lens effect is created.
« Last Edit: June 10, 2020, 12:11:45 PM by galfert »
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Offline funsutton

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Re: What else can cause a stray UV spike?
« Reply #10 on: June 10, 2020, 12:23:50 PM »
Quote
Maybe your sprinkler system ran at that time or there was a light rain.

It was fairly overcast here during the first part of the week, so a light rain is possible. I'd think I'd get more than a minute out of it though and that it would register on my other devices. I checked my video footage of the yard and didn't see any lightning or anything else out of the ordinary.

I did see a ton of lightning bugs in my yard last night though, which makes me wonder if one landed on it for a moment and lit up.

Probably more likely just a glitch.

Offline Mandrake

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Re: What else can cause a stray UV spike?
« Reply #11 on: June 10, 2020, 02:06:16 PM »
We don't get lightning bugs (rarely) and on the occasion I have seen a spike I have not been able to account for it by moisture/lightning or other means.
I suspect its more than likely just some error in coding that occurs on certain values of Lux or just is susceptible to random stuff!
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Offline lemuba

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Radiation/UV-Glitches 7 in 1 Sensor
« Reply #12 on: June 11, 2020, 09:57:16 AM »
http://www.ecowitt.com/weather_station/3.html

I run this and addition the GW1000 (from Froggit Germany)

Whatīs your experiance regarding the light sensor? I recently have glitches/spikes above 2000 W/mē, but also the overall tracking according to the sun Azimuth does not match very well.

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How is your experiance, should I claim this because itīs toooo worse/out of specs?

Grpahs taken during clear sunny days, no dust, dirt or rain drops on the sensor.

« Last Edit: June 11, 2020, 10:01:01 AM by lemuba »

Offline Mandrake

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Re: Radiation/UV-Glitches 7 in 1 Sensor
« Reply #13 on: June 11, 2020, 11:24:27 AM »
As with the similar thread on this forum about the spikes, its about normal.
The sensor is one of the weaker areas on the all-in one and really should be only used as a indicator rather than a precision instrument!

It has been suggested to Ecowitt that they look at a stand a lone precision sensor for those that would like more calibrated and real readings of UV etc and they took it on board but no promises if it will ever arrive as a product though their track record is excellent in turning these around so we will see!
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Offline galfert

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Re: UV Readings
« Reply #14 on: June 11, 2020, 11:45:09 AM »
I merged the threads. Look up for reference regarding this issue. Please read (or search) before posting a new thread. This other thread was just two line items down and had been posted in within the last day.
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Offline Autofill

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Re: What else can cause a stray UV spike?
« Reply #15 on: May 12, 2022, 05:39:41 PM »
I too, on occasion get solar/UV spikes and usually happens just after the rain and when the sun comes out, and attribute it to water being on the lens (as was already suggested). It doesn't happen often, but it has already happened once with my new WS90/Wittboy.

Turns out, there is a phenomon called "Cloud Edge Effect" I just realized that this could be also be controbuting to the random spikes that observed with the Ecowitt solar/UV sensors. This is known phenomemon in the solar voltaic communiity, where solar panels can produce close to their 100% maximum performnace for brief periods of time, because of solar radiation being reflected from passing clouds to the surface.

Next time this happens to you, take note if there are broken clouds.
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Offline Ronald H Levine

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Re: What else can cause a stray UV spike?
« Reply #16 on: September 05, 2022, 01:20:12 AM »
Anomalous UV of 14 spike at 3:19 P.M.!  Please explain here and by email: RonaldHLevine4548@yahoo.com Station: https://www.wunderground.com/dashboard/pws/KUTSANDY121?a=a Look at the huge narrow spike on the UV graph.  What could cause that?
My thoughts: IF it's generated internally by the system, then I can ignore it.  BUT IF it's caused by a celestial event such as a huge X-Ray or Cosmic Ray burst of energy, then it should appear on all devices everywhere at the exact same time and I want to know!  I was sunbathing at the time and very aware of the sky.  Blue cloudless sky and full sun and no odd events.  Could it be a hole or rip in the ozone layer passes by overhead to produce a huge yet brief UV spike?  RonaldHLevine4548@yahoo.com

Offline sky_watcher

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Re: What else can cause a stray UV spike?
« Reply #17 on: September 05, 2022, 03:44:11 AM »
Anomalous UV of 14 spike at 3:19 P.M.!  Please explain here and by email: RonaldHLevine4548@yahoo.com Station: https://www.wunderground.com/dashboard/pws/KUTSANDY121?a=a Look at the huge narrow spike on the UV graph.  What could cause that?
When I saw a large spike once, it appeared to be caused by a drop of water sitting on top of the sensor window - I could easily get to the head as it is sitting on the top deck of my houseboat on a short pole.

The droplet appeared to focus the light onto the sensor sending it high. I draw this conclusion because when I removed the droplet the reading dropped.
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Offline Autofill

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Re: What else can cause a stray UV spike?
« Reply #18 on: September 05, 2022, 04:36:26 PM »

Except, it does not measure UV directly, rather it calculates it via luminance, so either the sky got very bright or sun got reflected into it via a plane or some other reflective surface, or internal noise.

Anomalous UV of 14 spike at 3:19 P.M.!  Please explain here and by email: RonaldHLevine4548@yahoo.com Station: https://www.wunderground.com/dashboard/pws/KUTSANDY121?a=a Look at the huge narrow spike on the UV graph.  What could cause that?
My thoughts: IF it's generated internally by the system, then I can ignore it.  BUT IF it's caused by a celestial event such as a huge X-Ray or Cosmic Ray burst of energy, then it should appear on all devices everywhere at the exact same time and I want to know!  I was sunbathing at the time and very aware of the sky.  Blue cloudless sky and full sun and no odd events.  Could it be a hole or rip in the ozone layer passes by overhead to produce a huge yet brief UV spike?  RonaldHLevine4548@yahoo.com
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Offline Honusnap

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Re: What else can cause a stray UV spike?
« Reply #19 on: November 28, 2022, 05:04:36 AM »
Hello all,

I just added my Battery BMS to Home Assistant, i got 3.9kW PV, which mean i multiply the sensor value by 3.9 to have my virtual power available at the PV. Well .. the result is far under what PV deliver, meaning the sensor is completly OFF .. !!! I got to multiply between 10 and 12 to have something that look realistic. (realistic = at least as good as what my inverter push in my battery).
I checked sensor and it's full of condensation... do you have this problem too ? Or is it a warranty case ?

Thanks

Offline Rover1822

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Re: What else can cause a stray UV spike?
« Reply #20 on: November 28, 2022, 08:12:43 AM »
Quote
i got 3.9kW PV, which mean i multiply the sensor value by 3.9 to have my virtual power available at the PV.

I'm confused. The value supplied by the sensor is W per meter squared. How many square meters is your solar array? So, I believe you should be taking the sensor value times the # of square meters of your array, which would give you the potential power available in Watts.

Also take into account the angle of  the panel and that of the sensor, and the inefficiency of solar panels, the efficiency of your charger, the SoC of your batteries, and other things. But your potential available power should be way higher than your solar panel production.

what is 3.9kW , is that the nameplate rating of your array?, or is that the actual measured power output?

For me to measure efficiency, and I have a smaller array of 1.750kW (1750W) name plate , which should not be used for efficiency calculations. An efficiency for power produced is something like this . using my numbers from sensor, and measured power from solar

Sensor value * square meters of solar.  So right now   194W * 11 = 2134W , this is the total available right now for the area of the array which is 11 square meters

Now, for what is actually being produced from the array, at the same time, 230W

So efficiency is 230/2134 = 0.108  or near 11% , which is realistic









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Offline Honusnap

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Re: What else can cause a stray UV spike?
« Reply #21 on: November 28, 2022, 01:36:13 PM »
I got 3.9kW of PV, this is their power under 1000w/m2... so i just have to multiply the x w/m2 by 3.9.
When the sensor will detect 1000w/m2 .. my display will be 3900w.

By doing that, the result is always far under what my inverter output, by an other factor 2.5-3 or so.

Green : Light Sensor (x3.9 already)
Yellow : 48V Inverter output (not counting AC output, this is just power output to the batteries), but AC was pretty low, like 200w.
« Last Edit: November 28, 2022, 01:38:31 PM by Honusnap »

Offline Rover1822

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Re: What else can cause a stray UV spike?
« Reply #22 on: November 28, 2022, 02:10:29 PM »
You really need to post this in a solar panel or renewable energy forum, I belong to a few.

The name plate rating of your system at 3.9 kW is under laboratory conditions at STC, measured at a perfect 1000w/m^2 , which is really not achievable in real life, and can't be used as a reliable coefficient.

Please provide the values from your sensor , and the actual (measured) wattage input from the solar (taken at the same time), and the size of your array in square meters. 

You are still not providing the size in area of the array. (This would be the size of each panel x # of panels. Not the physical space it occupies, other words don't include gaps between panels)

Edit, if if you use the 3.9kW value, which you shouldn't, it is 3.9kW/(the m^2) of your array . You need the live value of kW production from the array, the value of the sensor and the area in m^2 of the array. Or none of the equations will work

Edit2: The value of your sensor is for 1 square meter, you surely don't have 3.9kW name plate solar in one square meter. But again, ignore the 3.9, you want "live" watt data from the array. I know because I do track the live wattage output from mine. Right now, I have no evidence that there is an issue with your sensor

« Last Edit: November 28, 2022, 02:54:32 PM by Rover1822 »
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Offline mcrossley

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Re: What else can cause a stray UV spike?
« Reply #23 on: November 28, 2022, 05:00:19 PM »
The PWS solar value is for a horizontal plane. I doubt your panels are horizontal, so you must apply a correction based on the solar angle to the panels at the current time - plus the factors for area and efficiency. It's not simple.
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Offline davidefa

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Re: What else can cause a stray UV spike?
« Reply #24 on: November 28, 2022, 05:03:34 PM »
I think you should wait for a day with full sun, you should see two sinusoidal waveforms ( easier to compare ).
You should have your batteries 'half charged' to be sure they will accept 100% of the charge provided by your PV system.
The graph you posted shows that the charge accepted by the batteries decreases while 'sun power' is increasing.
A time scale on x axis could be useful.

P.S.
Sorry for the dumb question, but is an mppt controller present in your system? What are the batteries specs? How is composed your system?

P.P.S.
Forgot to add that the condensation inside your sensor is not normal. Is your sensor a ws65? I think not easy to remove without opening the sensor assembly
« Last Edit: November 28, 2022, 05:12:21 PM by davidefa »