Measuring Current from 10pA to 100nA

Discussion in 'Programmer's Corner' started by farobin, Jul 29, 2012.

  1. farobin

    Thread Starter New Member

    Jul 27, 2012
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    0
    Hello Everyone,

    I almost know nothing about circuit designing, apart from undergrad electronics. For the instrument I am designing
    for Radiation Dosimetry application, I have to be able to detect light
    with photo diode generating ~ 10pA to 100nA. Currently I am using Keithley
    Multimeter. But my system has to be handheld. Could you please give me a
    guideline how do I design a circuit to be able to detect this current range?
    Any help will be highly appreciated.
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    First, I think this should not be in Programmers corner, because it wont´t get too much attention here.

    Second, look at Dave´s uCurrent and see if you could adapt that schematic.
    http://www.eevblog.com/projects/ucurrent/
     
    Potato Pudding likes this.
  4. takao21203

    Distinguished Member

    Apr 28, 2012
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    currents in this range are problematic to measure, because common EMI will induce such currents. Good shielding is essential.

    Radiation detector based on photodiodes are possible and have been built, however they have noise problem vs. sensitivity.

    Also these don't use small standard photodiodes, but special, large PIN diodes.
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    This should be my field of work but I would have to dig into the books to make it work.
    Usually we would use a PMT. Any particular reason for using a photodiode, apart from portability?
     
  6. farobin

    Thread Starter New Member

    Jul 27, 2012
    2
    0
    Thanks everyone for suggestions.
    I would use PMT but HV required by PMT is a problem
    for portability, and in the wavelength range 750nm, PMT sensitivity
    falls rapidly. Infact for testing in the lab I used PMT, PD, CCD...but PD seems to be most user friendly for people and the cheapest.
    I contacted with TI, but they also suggested about forums.
    So kind of struggling to start with.
     
  7. ScottWang

    Moderator

    Aug 23, 2012
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    Last edited: Sep 21, 2012
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