>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>On Behalf Of Mike Hord
>Sent: 29 November 2004 15:54
>To: Microcontroller discussion list - Public.
>Subject: [EE] UV-B detection schemes
>
>
>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?

EPROMS tend to take longer to erase the more they are programmed and
erased IME, which would skew the results.  You can buy UVB sensors from
http://www.imagiworks.com/Pages/Products/Sensors/UltravioletSensors.html
for about the cost of one of the aquarium lamps.

Regards

Mike

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