UVA, uvb and light meters

[Kaizen]

Just a quick question: I see that there are a multitude of uv light meters out there—all claiming to measure radiation between 280 and 400 nm; but none seem to indicate how much of what kind of uv is being detected. Since the particular wavelength of uv light responsible for d3 production is only a small band between 290 and 310nm, and since (presumably) any uv meter will give the same uv reading so long as the light emitted is anywhere between 290 and 400nm, aren’t such devices misleading at best, and useless at worst? How do we know that the uv our meters are detecting is uvb within the right wavelength range? As an example:

Say we have two light sources, 1 and 2

Light source 1 emits uv light between 320 and 380 nm.
Light source 2 emits uv light between 280 and 320 nm and at the very same intensity as light source 1.

A uv meter sensitive to uv light will give the same reading for both sources, but light source 1, will be useless as a d3 light.

Thoughts?

 

[Lunatuck]

That sounds about right. But I wouldnt say useless. It should help you track the deterioration of the elements in the bulbs that are putting out the uvb.

A rough assumption is that the UV light is dropping equally. So watching the detectors output should help determine bulbs usefulness. Also helps for A-B comparisons.

I dont know if it exists, but a UVB filter or film over the detector, or any sensor sensitive to uv light could give a good platform for testing. Ive done some interesting photon counting experiments for astronomy. Of course my filters cost more then my camera.

 

[jamest0o0]

Would like to hear responses, @nightanole maybe you have thoughts on this?

 

[Kaizen]

I agree that a uv meter would help track bulb decay; but even then, it won’t track the decay of uvb output alone, it will only track diminishing uv output as a total. This is my ignorance, but do we know if any of these bulbs lose uv intensity uniformly across the uv spectrum? For instance, it might be that the uvb output diminishes faster or slower than the uva output. The fact is I just don’t know, and a uv meter can’t tell me.

 

[Lunatuck]

It looks like there is a UVB solar meter.

I can't answer your question otherwise. UVB bulbs must use either a special coating on the florescent tube and a special glass to allow the UV light to pass. I suspect they're still mercury based as it appears mercury will put out light in that wavelength.

 

[SharpShooter]

It looks like there is a UVB solar meter.

View attachment 227237

I can't answer your question otherwise. UVB bulbs must use either a special coating on the florescent tube and a special glass to allow the UV light to pass. I suspect they're still mercury based as it appears mercury will put out light in that wavelength.

Call me a cynic but those are identical units rebranded for each company looking at them.

 

[Clayton0520]

So your not gonna find a commercially produced lamp that is that “fine tuned” for the specific wavelength of 280-315nm ( where the UVB spectrum is found ) with that being said your also not gonna find a power meter/index meter/wavelength meter that a hobbyist can afford. So we are a stuck with the cheaper version meters that we can afford. Keysight, MDF, and Motorola offer wavelength meters that can tell you your exact readings all for about 15 grand! With that being said I have a Solameter 6.5 that I believe is a sound investment. You will be VERY surprised with your readings. With out any meter you are completely blind with a hobbyist meter a least you have a better idea of what is actually getting into your enclosure.

 

[Kaizen]

Hmm, you raise a rather good point. Especially as the alternative is either 15k, or else being totally in the dark (light joke...I know...couldn’t resist). Thanks for the dose of pragmatism; I occasionally get carried away by the devil in the details at the cost of seeing the big picture.

 

[iMi]

Call me a cynic but those are identical units rebranded for each company looking at them.

Not a cynic. I can tell you for a fact that very few factories make them. They are all coming from the same source. This is common. I have been to so many, many factories in China, Taiwan and Vietnam and it’s funny to see various brands side by side in the same factory. The world is such a small place.