I am experimenting with an EPROM as a detector.

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Postby ruudl1952 » Mon Oct 22, 2012 12:00 am

I was planning to make a UV meter using an EPROM. The idea was that ultraviolet light erases an EPROM. When a fully programmed EPROM (all zoreo's) is exposed to uv light I should clearly see the number of bits (one's) increasing.
So I have built a small device that counts the number of bits (one's) in an EPROM.
I had guessed that the speed of increase of bits would certainly be a measure of the UV intensity.
But...
When exposing the EPROM to uv-light I expected a smooth and stable increase of bits, but that didn't happen. In stead, after some time of exposure to uv-light the bitcount begins to vary because of the bits (all Floating Gate devices) become unstable.

Knowing that the bits become unstable, I covered the EPROM window with aluminium and watched what would happen.
As I expected the bitcount kept varying (I measure 64k bit 4 times per second). I have a built in threshold of 50, and everytime 2 measurements have a difference of 50 of more I show a flash on an LED.
The device is flasing very randomly between 20 to 60 flashes per minute. Now my question is: What is it that I measure? Clearly,some effects help to flip the very unstable bits, but I don't know what it is that makes them flip.
It is more than just random flips, because I notice patterns over time. Can anyone give me a clue?

(Ik had geen zin om mijn tekstje te vertalen... Je mag gewoon in het nederlands antwoorden! )
ruudl1952
 
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