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Voltage Drop across Capacitor?

  1. Jul 28, 2008 #1
    Hi all,

    Here's the problem!

    I am attempting to create a leakage current test suite. Basically it centers around cutting the voltage reference supply to a capacitor and measuring the voltage drop. Similar to the one in the attachment.

    I figured that to determine the drop it would be a simple case of V at start minus V after time delay.

    However a colleage told me that because of the exponential decay of capacitors this simple equation wouldn't be enough to accuratly determine the voltage drop.

    Any ideas?


    - Si

    Attached Files:

  2. jcsd
  3. Jul 28, 2008 #2


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    Staff Emeritus
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    Homework Helper

    I'm assuming you want to measure the parallel resistance (which causes the charge to leak) of the capacitor.

    You can use an exponentially decaying function for the voltage:

    V_t = V_{ref} \ e^{-t/(RC)}
    where Vt is the voltage after t seconds. Solve the equation for R after measuring all other quantities (Vt, Vref, t, and C)
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