Impedance Z caculation

Discussion in 'General Electronics Chat' started by DreamCatch16, Feb 10, 2014.

  1. DreamCatch16

    Thread Starter New Member

    Feb 10, 2014
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    Hi,

    If we have the voltage V = A sin(ωt) and the current I = B sin(ωt+θ)
    How to calculate the impedance Z? (Real and imaginary parts)

    Thank you for your help.
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    V=I*Z
    Z=V/I

    You will need to rewrite the sine in order to separate real and imaginary parts.
     
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  3. DreamCatch16

    Thread Starter New Member

    Feb 10, 2014
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    OK but how to express V/I as a complex number from where we derive the real and imaginary parts of the impedance

    Thank you for your reply ;)
     
  4. DreamCatch16

    Thread Starter New Member

    Feb 10, 2014
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    Please can any one guide me or give me a reference for how to calculate the impedance using the DFT

    Thank you in advance
     
  5. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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  6. DreamCatch16

    Thread Starter New Member

    Feb 10, 2014
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    Thank you t_n_k for your reply

    now is clear that using euler formula we can deduce that the magnitude of |Z|= A / B
    and the phase is simply θ which is the pahse differemce between the voltage and the current

    :D

    for the DFT I want to make samplings of both the current and voltage using a microcontroller and I read that by the DFT I can calculate the impedance but I didn't find a reference where they explain clearly how is it done.

    Thank you for your help :)
     
  7. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    This statement seems self contradictory. You have "read" that it's done by using DFT but can't find any reference to how it's done. Where did you read the claim in the first place?

    Presumably you want to excite some system with a source [voltage] waveform having a multi-frequency distribution. You would sample / capture the [current] response and infer the complex impedance at each available spectral frequency, by applying the discrete fourier transform to the sampled source and response waveforms.
    One could then plot the impedance as a function of excitation frequency. Is this what you mean?
     
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