Is there a simple or at least an inexpensive way to measure the spectrum=20
of a light source?

On 1/15/2013 7:34 AM, RussellMc wrote:
> Russell said:
>
>>> UV LEDs producing even a few mW of power have until recently cost
>>> hundreds of dollars.
> Seam said
>> Hmmm again. I recently bought some UV LEDs on eBay for about US $0.50
>> each. Supposed to be 385nm wavelength. When I tried one, it produced a
>> faint visible glow - whiteish blue if I recall correctly, but it
>> definitely could make UV-sensitive materials fluoresce (like the
>> security bands in US paper currency). Have I been duped or has there
>> been a recent breakthrough that makes these kind of UV LEDs cheap? It
>> also seems to me that I've seen tiny "blacklight" pens for several
>> years now which are intended to check for valid currency. These seem
>> to be using LEDs. Am I wrong? The output of these devices definitely
>> is not bright blue light.
> or, Russell could be wrong :-).
> But, it's all relative and I should have added even more detail.
>
> David said:
>> I've use these ones from Element14 before:
>> http://au.element14.com/vcc-visual-communications-company/vaol-5guv0t4/l=
ed-5mm-ultraviolet-160mcd-405nm/dp/1712756
> I note in that data sheet that one application is "germicidal" use.
> I think they are being a bit naughty.
> They would probably give some living things a harder time but they are
> well away from what is usually deemed "germicidal" wavelengths.
>
> There's UV and there's UV and there's UV and ther's sort of almost UV
> - and I could hav ebeen more specific.
>
> UVA  320- 400 nm
> UVB  290 - 320 nm
> UVC   190-290 nm
>
> The A/B and B/C bounday figures vary by about 10 nm between sources.
> All seem agreed that uVA starts at 320 nm - but even that is arbitrary.
>
> Dave's LED
> datasheet ->
> http://vcclite.com/wp-content/files/VAOL-5GUV0T4-LED-5mm-UV.pdf
>
>   is listed at 405 nm in the heading and has bins of 400-405 and 405-410 =
nm.
> Neither is quite UV by definitions above BUT the light is energetic
> enough to cause fluroesnce in many materials and to distress some
> bugs.
>
> Suntanning is generally caused by YVA range light.
> Sunburning is generally caused by UVB.
> Don't take that as gospel - UVA can burn you - BLUE light can burn you
> - some parts of you more than others.
>
> This extremely good (IMHO) overview of UV safety gives a good picture
> of relative dangers at various  wavelengths
>
> WELL WORTH LOOKING AT.
>
>      https://www.case.edu/ehs/Training/UV/UVsafety.pdf
>
> It explains what wavelengths are stopped where and by what and the effect=
s.
> The real nasty is UVC which is emitted by tyhe sun and by true
> "germicidal" lamps.
> However, solar UVC is absorbed by the atmosphere. UVC from eg uncoated
> mercury tubes can be hazardous tens of metres in air from its source.
>
> They say:
> .
> Germicidal lamps or low pressure mercury lamps are
> commonly used in laboratory. They are usually in housed
> fixtures such as a biological hood, but may not always
> limit exposure to the eyes or skin. The UV wavelength of
> these lamps is between 200-280 nm and work by
> breaking DNA which removes the capability of organisms to
> reproduce or kills them.
> Unprotected persons should not
> be in a room where a lamp is
> active. Hood lamps should be
> turned off after sterilization
> time has ended.
>
>
>
>       Russell

--=20
John Ferrell W8CCW
That which can be destroyed by the truth should be.
P.C. HODGELL
  =20


--=20
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