Actually the UV eprom sounds like a simple enough method.
        Write a byte with Zeros
Loop:   delay ~1 minute
        Read byte
        Increment counter
        if Zero Loop
        Compare counter with previous count

Might also want to look for counter overflow

KF4HAZ - Lonnie

----- From: "Mike Hord" <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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