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LDRs and intensity

Discussion in 'General Electronics Discussion' started by eptheta, Jan 24, 2011.

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  1. eptheta


    Dec 20, 2009
    I am slightly confused.
    I was doing a little experiment where I passed red light through a blue/purple solution and measured the light intensity at the other end using an LDR.

    I varied concentration and got all the data i needed.
    I wish to see how concentration affects light intensity by plotting a graph between resistance and concentration, however, I can't figure out how to use resistance correctly.
    I know that concentration and light intensity are anyway a lograthmic relation(Beer Lambert's law)
    -log(I/Io) (proportional to) conc

    What is the relationship between resistance and intensity? Is it a log function as well ? The datasheet it shows this:
    Am i getting the units wrong or something ?


    EDIT: sorry if the graph isn't clear, you can look at the datasheet yourself
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Wow. Looks like a perfect log/log relationship.
  3. eptheta


    Dec 20, 2009
    Oh God I'm stupid. Sorry, didn't see the scale, just the units. I expected to see log(R) and log(I).
    In my defense, I posted this around 3:00 am.
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