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.

 

V=I*Z
Z=V/I

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

 

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

 

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

Thank you in advance

 

You don't need DFT to solve this.

Perhaps this might help .....

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/impcom.html#c1

 

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



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

 

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.

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?