# SolarMeter 6.2 or 6.5



## Alxsparks (May 15, 2013)

I've resigned myself to getting a SolarMeter, but I've read a lot of great things about the 6.2 and the 6.5. I know the 6.2 concentrates on UVB (although I've read things about it not concentrating on the right UVB (either too much or too little)), and the recommendations are for 6.5 are pretty great, but it takes the UVI, and I'm not sure if that's the number I need.

Any suggestions?


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## Josh (May 15, 2013)

Seems like the 6.2 would tell you more about the part you care about. It looks like it might be hard to determine UVA/UVB from a UVI reading... I'm not positive though as I've never used a Solarmeter


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## Roadkill (May 15, 2013)

Neither is as accurate as people want to think they are. I just came from a workshop a couple weeks ago where we compared the Solarmeter 6.2 to a proper UVB Spectrometer, and the results were rather interesting. Under "dim" artificial lighting, the actual UVB output was about 30-40% of what the Solarmeter 6.2 said it was. Under bright, full sunlight, the actual UVB was about 10% what the Solarmeter 6.2 said it was. This doesn't mean the Solarmeter is crap, but when you look at their response curves, it is clear they are still somewhat sensitive to wavelengths that are really not that good for Vitamin D3 production. The Solarmeter 6.5 is even more sensitive to a greater range of wavelengths, and so would be even more "inaccurate" for determining if your bulbs are producing usable UVB.


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## Alxsparks (May 15, 2013)

Roadkill said:


> Neither is as accurate as people want to think they are. I just came from a workshop a couple weeks ago where we compared the Solarmeter 6.2 to a proper UVB Spectrometer, and the results were rather interesting. Under "dim" artificial lighting, the actual UVB output was about 30-40% of what the Solarmeter 6.2 said it was. Under bright, full sunlight, the actual UVB was about 10% what the Solarmeter 6.2 said it was. This doesn't mean the Solarmeter is crap, but when you look at their response curves, it is clear they are still somewhat sensitive to wavelengths that are really not that good for Vitamin D3 production. The Solarmeter 6.5 is even more sensitive to a greater range of wavelengths, and so would be even more "inaccurate" for determining if your bulbs are producing usable UVB.


 
Is there something you would recommend instead?

I've also read that the 6.5 is the only way to compare bulbs to sunlight or even to other brands of bulbs because of different spectrum ranges for various manufacturers... There's also a 6.4 which estimates the range for D3 production, although it's the same sensor as in the 6.5 and the two numbers are based on the same information (you can get the solarmeter 6.5 reading by multiplying the 6.4 reading by 0.14, according to one site.

I think the value of the 6.5 is that you can compare UV conditions in the habitat to readily available information (the UV Index) out doors or in the animal's native home. I guess the question is whether or not that's valuable?


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## Roadkill (May 15, 2013)

Problem comes in understanding what you want and being able to afford it. If what you want is to get the intensity of the UVB range that is most effective at Vitamin D3 photoactivation, then the Solarmeter 6.2 is still your best bet. It still works fine as long as you understand its limitations. The problem with both the 6.4 and 6.5 is the higher sensitivity to the lower wavelengths, this will radically alter the reading it gives depending on the wavelengths in the lower ranges. While the 6.5 is relatable to the UV index we hear on the news, again you find yourself asking "Ok, but what specifically about those wavelengths that produce Vit.D3?". The UV index doesn't really proportionally relate to this UNLESS you know the intensities of the individual wavelengths involved, and if you know that, then the UV index is a pointless step. Or to put it another way, from a bulb you could get a UV index of 3, and from sunlight you could get a UV index of 3, but because of how the UV index is arrived at, even though those both have indexes of 3, it DOES NOT mean that all the wavelengths involved in both measures are equal. 
There are certainly more accurate equipment out there, but we're talking a massive step in cost. Is it worth it to the average person to pay a couple thousand dollars to get a proper spectrometer that measures strictly the UVB wavelengths that produce Vit.D3 just for checking bulbs? I'd say no.


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## Alxsparks (May 15, 2013)

Thanks for the insight. It's been very helpful. You've obviously done your homework.


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## Alxsparks (May 16, 2013)

As a follow-up, sent Solarmeter an email to get their views. Essentially they seem to say that the 6.2 is good for reptiles, and while the 6.5 is useful, and measures light that is closer to the D3 spectrum, it also might not be as accurate for what we're looking for (which confirms Roadkill's point, so: Spot On Roadkill!).

Here's the actual text of the response:

Most people just use the 6.2. It reads out a larger number easier to check lamps when new and replace when down 30% from new. Some people also use the 6.5 to make sure the UV Index is not "too much" at basking position... because a few years ago some lamps were sold that had a lot of short wave UVB and thus the UVI was higher than they would experience in nature. Such lamps can also cause eye damage. But most have been removed from market - or so I've been told.

Either meter can be used for lamp aging tests. The 6.5 is closer to D3 action spectrum.. but might read tiny number to some low wattage fluorescents. All of them are now the version for both sun and lamps.

Forget about the 6.4 meter. It is for humans not reptiles.


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## Josh (May 16, 2013)

Thanks for following up so we can all learn about this. I wonder if we can get them to post here and answer all our questions


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