-yes, the cheap one lists power consumption, the Nichia āradiometric outputā, you can not use the lumen because the lumen measures visibility by the human eye and 365nm is completely invisible, it would be always zero lumen. Output of the 3W led could be 500mW though if it is any decent. 500mW is very ok for a 365nm led, although the latest ones emit 1000 mW, some even more. The cheap ones that I have seen thusfar emit apart from the UV quite some visible light that may obscure the fluorescence light that you want to see when using the UV (the visible light from the led may be blocked by using a UV-pass filter in front of the led, like a ZWB2 or UG1 filter). Nichia 365nm leds are known for emitting very little visible light aside from the UV.
-measuring UV is not straightforward unless you buy a special device for it. I myself have devised a makeshift method by measuring copier paper fluorescence in a standardised way, but I do not claim a great accuracy.
-from around 300nm and up standard glass will transmit close to 100%, but the 280nm deep UV leds need quartz glass (other name: fused silicon), indeed polycarbonate has a cut-off around 400nm, PMMA is a little lower, it transmits most of the 365nm radiation.
those UV LEDs are very sensitive for overheating and have a way lower thermal damage temperature than white or blue LEDs
you want a DTP star or at least a copper star with a thick layer of copper to spread the heat
if you use a DTP star you can heatsink the cathode way better, but you have to insulate most hosts from the PCB with a Kapton tape or similar stuff
For some reason even though I am using 395nm (from a reliable source) I managed to wreck some LEDs and optics today.
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Iāve been using plastic fresnel lenses with these and had no problem so I sort of assumed this would work too, but I guess not LOL
Are the clear polycarb glasses what is needed for the 280nm as well?
EDIT: Also when you say the 280nm āneedsā Quartz glass what effect are we talking about if I were to try and pass it through standard glass? Loss of āsomeā light? āMostā light? Serous danger like the lens could explode etcā¦?
Yes, for 280nm you want the polycarb glasses as well, the wavelength is more harming to your eyes (and skin!) than 365nm, but luckily the leds at 280nm put out way less light, typically a few mW (although there are recently 280nm leds out there with 70mW output)
All normal types of glass transmit very poorly at 280nm, only a few percent.
No, I have not tried a standard meter, they are quite expensive, Iām not sure if they are much more accurate, and I do not that many uv-led tests. And I like my amateur-way
My method has three flaws: 1)it is not calibrated to anything, 2)it is somewhat sensitive to beam profile, 3)during tests the paper shows some bleaching so the output at the highest currents read a bit lower than they should.
Still an extra 500mA should be measurable, in fact I think the current at which the maximum output is reached is measured quite reliably.
Does anyone know if there is a standard distance that UV is measured at. Like when we measure white light in CD? I have a UV meter now any it measures in cm/2, but Iām not sure how far away I should be or if there even is a standard.
What do you want to measure?
Only relevant units for measurents of UV lights are peak wavelenght in nm, power consumption in W and Luminous flux in lm.
Luminous intensity doensāt matter with UV, but beam angle does. Since most UV flashlights are throwers, the very small amount of flooders is interesting for practical use when searching areas.
Milliwatts per square centimeter is what I have been using. I can just point the light source at the meter and get this, but no where in any of the documents I have found is a standard distance from the meter this is suppose to be measured.
How did you come to use mW/mĀ² and what do you expect to gain with this combination?
Since specs for emitters are public, you could just calculate this data.
