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Need MA to voltage converter help

Discussion in 'Electronic Design' started by Jim, Oct 9, 2008.

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  1. Jim

    Jim Guest

    I have a sunlight sensor made up of 2 tiny amorphous solar cells in
    parallel, that I would like to use with a 0-5 volt data logger. These cells
    provide the spectral response I want.

    The cells together generate a maximum of 2.25ma of current in full sunlight
    that I need to convert to voltage.

    I have used a OP90 op amp in the past to do the same for other sensors, but
    only for microamp currents. I did the math to find the value of the
    feedback resistor for this, and come up with something like .0022 ohms which
    doesn't seem too workable. Either I am making a mistake in my math or maybe
    it isn't possible to do this conversion using a single op amp.

    Can someone give me an option for making this a>v converter for this 2.25ma

  2. Tom Bruhns

    Tom Bruhns Guest

    Not sure how you came up with that resistance value, but I'd suggest
    you revisit your calculation. When I do it, I get 5V/.00225A = 2.22k
    ohms, not a bad value at all. Looks like you lost 6 orders of
    magnitude somewhere.

    (It's always good to double-check your answers, especially in cases
    like this where the result seems odd. For example, 2.25mA times .0022
    ohms is 5 microvolts, not 5 volts. In other words, plug your result
    back in to do the checking so you're lest apt to make the same mistake
    over again.)

  3. Tom Bruhns

    Tom Bruhns Guest

    On Oct 9, 5:03 pm, Jim Thompson <[email protected]> wrote:
    Just solved the world's energy crunch, if so! ;-)
  4. Rich Grise

    Rich Grise Guest

    When I first read the OP, I misread it as nanoamps. ;-)

  5. neon


    Oct 21, 2006
    What is your problem you do not believe that current thru a resistor will give you voltage? by using the proper resistor you can scale it to anything you desire .
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