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Cheapest way to check if a UVC bulb is as advertised?

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Someone:

--- Quote from: pipe2null on April 03, 2020, 10:40:13 pm ---Lots of good feedback, thanks!


--- Quote from: Someone on April 03, 2020, 09:12:57 pm ---Cheaply quantifying spectral energy, not really possible. Doing it below 300nm, another order of magnitude more expensive at least. Without an accurate and stable spectral output the cheap methods to quantify energy are all useless.

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Yea...  That is what I figured, thus my inclusion of the " :-DD" emoji next to the word "ideally" in the OP.   ;)
A spectrum analyzer or VNA is on my to-buy list, but wasn't intending on picking one of those up until next year.  I think I read somewhere that SAs are used with a special probe for wavelength measurements?  I have a scope and a miscellaneous assortment of bits n pieces, had hoped cobbling together a makeshift probe for use with my existing scope might have been possible, but I really did not expect it.
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A spectrum analyser measures RF/audio frequencies in a voltage source, visible light frequencies are over the terahertz gap at 500THz, UV even further. There aren't practical circuits at these frequencies so all the "processing" has to be done in optics.


--- Quote from: LaserSteve on April 03, 2020, 11:38:32 pm ---A metalized, reflective mode. diffraction grating and something that is florescent is all you need. It helps if you have a neon lamp (NE2 is fine), HG based germicidal lamp,  or a old CFL lamp for rough calibration.

Quartz, Fused Silica, or Calcium Fluoride  prisms are out there, but would be a pain in the neck to use compared to a  1200 LPI grating.
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That will help pick the emission wavelengths (assuming the fluorescent material lines up with the emission) but doesn't help with quantifying the source energy.

Siwastaja:

--- Quote from: Zero999 on April 03, 2020, 11:06:07 pm ---Yes, mercury lamps are much more efficient, than UVC LEDs. Going by the data sheet, 30% seems to be fairly typical. Of course this doesn't taken into account the losses in the ballast, but an electronic ballast will have similar losses to a switched mode LED driver.
https://www.ushio.com/files/specifications/germicidal-low-pressure-mercury-arc.pdf

I know you said in the other thread that UVC LEDs have a more optimal spectrum, but it's still isn't enough to offset it. I imagine LEDs might work out better if they need to be switched on and off very frequently, such as in a water dispenser, where the mercury vapour lamp would probably be on continuously, as people wouldn't want to wait for it to warm up, but that's about it. LEDs also don't give off any ozone which can also be responsible for the sterilising effect, especially in applications where some of the surfaces will be shaded. I know ozone is often unwanted and there are doped quartz lamps which filter it out.

I agree about investing in UVC LEDs, but I consider them too mature for use in all but the most niche applications. Mercury lamps are a mature, efficient, tried and tested technology.

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Yes, you are right. Except for the very short duty intermittent applications where the LEDs make real engienering sense, UVC LEDs are still more of an interesting concept, like white LEDs somewhere 1998 or so. But, if the pandemic increases funding for their development, it's quite likely we see the series of similar breakthroughs what happened in white LEDs within just 5-10 years around 2000.

Zero999:

--- Quote from: Siwastaja on April 04, 2020, 06:35:17 am ---Yes, you are right. Except for the very short duty intermittent applications where the LEDs make real engienering sense, UVC LEDs are still more of an interesting concept, like white LEDs somewhere 1998 or so. But, if the pandemic increases funding for their development, it's quite likely we see the series of similar breakthroughs what happened in white LEDs within just 5-10 years around 2000.

--- End quote ---
I hope so, but don't hold your breath. LED efficiency hasn't gone up equally for all wavelengths. There has been a massive increase in the efficiency of UVA and blue LEDs, but green and yellow still lag significantly. In theory it should be possible to produce make shorter wavelengths more efficiently, than longer ones, because a higher forward voltage should mean less I2R losses inside the semiconducting materials, but it doesn't always work out that way.

Siwastaja:
Yes, because it's a matter of finding the right materials and processes, with physical constraints, it can't be predicted. More resources and funding means higher chances, but the plain old luck is still part of the equation. It's likely there is a breakthrough, but no one can guarantee it.

You could say that yellow LEDs are still more inefficient because there is much less need, hence less funding for their development than for blue (i.e., white) LEDs, but it may not be that way, it's also a possibility that you just can't make them any better.

borjam:
I have an old EPROM eraser, a hobby unit for two chips maximum.

It indeed erases them in 15 minutes or so, and once turned on you can smell ozone. Which means that ionizing radiation is indeed being emitted.

It also degraded anti static foam.

So I guess the presence of ozone is a good hint. Moreover that ozone itself is bad for germs adding insult to injury :)

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