Forrest Mims (of the engineers notebook fame) did several articles on
monitoring solar radiation, including some surprisingly high quality low
cost sensors. IIRC he designed the 'Sun and Sky Monitoring Station' that
sells through Radio Shack for ~$25US

Googleing.......


Here's a link to his site <http://www.forrestmims.org/pages/7/index.htm>
And I tripped in these guys in the process <http://www.sglux.de/> (but I
don't know anything about them)

You might need to poke around a bit and find copies of his original
articles to get the details though.

-Denny




----- Original Message ----- 
From: "Mike Hord"

> I'd like to find a quick and dirty way to help a friend assess the UV-B
> output on the "big" lamps for his saltwater aquarium.  Apparantly,
> these lights are pricey ($90US) and recommended change time is
> ~9 months, as the UV-B drops off considerably after that.  The
> question is, does that UV-B light drop off sooner, or later?  This is
> important to the survival of the coral in his tank.
>
> All this info is second hand from him, so it could be right or wrong.
> I don't know.  He tends not to believe the manufacturer that the
> light should be changed in 9 months; after all, they want you to
> buy a new one as often as possible.
>
> So, how do I rate the UV-B content of the light?  The theory I have
> at the moment is to use a good ol' UV erasable EPROM, right
> some data to it, then periodically check the data for soundness.
> The amount of UV-B light should affect the data decay rate, and
> so if a certain amount of time passes without significant data
> loss, time to change the bulb.
>
> As indicated above, this is a long term study (months), so if
> the sensor needs to be left in place for the full 8 hours the lamps
> are on, that's okay.
>
> Input?
>
> Mike H.
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