UVB bulbs - what do we know??

[laurie]

Just wondering if anyone out there knows a lot about UVB blubs, I have a meter but still have a big question.

Over the lifespan of a UVB Florescent lamp, does the intensity of the light output (Lumens) decrease, or does the spectral output of the lamp shift out of the UVB range (315-280nm), or does it do both? If a shift in the spectral output does occur, in which direction?

 

[kinyonga]

You might get some answers here...
http://www.uvguide.co.uk/usinguvmeter.htm

 

[Dave Weldon]

Howdy Laurie,

From everything I've ever read and all of the conversations I've had with "experts" regarding issues about UVB sources, no one has ever hinted at a UVB spectral shift as the phoshpor ages from use . As we all know, the UVB decreases as the phosphor ages from use. Like normal fluorescent tubes, lumen output will decrease as the tube ages from use too. As an educated guess, I'd say that the rate at which the UVB spectral content and the visible light spectral content decrease from usage are not likely to be the same.

 

[summoner12]

Howdy Laurie,

From everything I've ever read and all of the conversations I've had with "experts" regarding issues about UVB sources, no one has ever hinted at a UVB spectral shift as the phoshpor ages from use . As we all know, the UVB decreases as the phosphor ages from use. Like normal fluorescent tubes, lumen output will decrease as the tube ages from use too. As an educated guess, I'd say that the rate at which the UVB spectral content and the visible light spectral content decrease from usage are not likely to be the same.

Yeah, I would suspect usable UVB is gone before the lamps lumen output suffers. The 'burn' marks on my UVB lamps don't get as dark as my 6500K lamps. I change a UVB lamp much sooner than a 6500K burns out.

 

[Venutus1]

Yeah, I would suspect usable UVB is gone before the lamps lumen output suffers. The 'burn' marks on my UVB lamps don't get as dark as my 6500K lamps. I change a UVB lamp much sooner than a 6500K burns out.

Yes!
The UV rays decay much faster than the other (visisble) light wavelengths...

So UV bulbs of any kind must be replaced long before they "look" dim or burn out.

Otherwise you really do risk jeopardizing the animals health and inviting MBD to wrack their little bodies.

Fact:
Better brands of flo. UV tubes last longer than cheaper ones-- that is to say, they have a much longer use-full life.
So dollar for dollar, actually the better brands that are made in Europe can actually COST LESS to use than the other kinds.

A Solarmeter 6.2 is the ONE tool everyone needs to be familiar with and should own or rent on a regular basis.

Or have a good friend lend them one every month or two to monitor their light set-ups.

Cheap flo. bulbs need to be replaced every 6 mo.
Real cheap Mercury Vapor bulbs ONLY LAST 3-4 mo. IF you are lucky!

Hint for new herpers:
Take a sharpie and always write the date on the new bulb when you are changing them.

Do not use any "off" brand or untested / untrusted UV bulbs.

Happy Herping & Happy New Year!
Todd
www.lightyourreptiles.com

Below are some pics I have taken in preparation for a study I am doing of different UV bulbs & how they work in different fixtures.

I put them up just to show how easy it is to test UV out-put.

All you do is gage the distance (to where the animal would be sitting/ basking) and push the button.

Basically it is just a push of a button.

In some of the testing I was doing below... I was also trying to gage how much loss you get from a particular mesh of screening.
Very interesting stuff.
Keeps me busy.

 

[Venutus1]

Just wondering if anyone out there knows a lot about UVB blubs, I have a meter but still have a big question.

Over the lifespan of a UVB Florescent lamp, does the intensity of the light output (Lumens) decrease, or does the spectral output of the lamp shift out of the UVB range (315-280nm), or does it do both? If a shift in the spectral output does occur, in which direction?

Hi Laurie.
oops...
I guess I missed the point a bit in your original post.
Well, you know me... I jump around allot.
Anyway...More to what you were talking about--

Yep, I am pretty sure that you have hit the nail on the head.
That the different wavelengths of UV in the lamps decay at different rates.
So the UV spectral "curve" of the lamp will change over time just as the visual light will.
Ever notice how full spectrum lamps yellow over time? That is because the blue phosphor is less stable than the yellow and will decay (or "wear out" ) faster than the yellow or green.
Therefore, side by side, a very old full spectrum 6.5K bulb will look "yellowish" when compared right next to a brand new full spectrum lamp of the same brand.
In other works, it isn't 6.5k either any more!

I believe if we could "see" the UV light,
then I bet we would see a similar shift like you see in the visual light output.

The UV spectral curve that is being produced as the light ages would change over time.

hmm...I wonder what UV nm wavelengths go first?
Is the UV b D3 295 the first to go ?....or the other UV wavelengths including & up into the UV A ones.
ahhh.. we may need to check with Frances.

BTW.
It will be to see how the new METAL HALIDES will compare to the flo. tubes & Merc. vapor we have been using over all these years.

From what I have heard, they are the cat's meow when it comes to a basking light that produces UV.
And the spectrum of light being given off is much closer to the spectral curve of natural sunlight than anything available. period.
They will be a HUGE game changer and probably make mercury vapor obsolete.

Cheers!
Todd