how to calculate harmonic current of AC input current

[alphi]

I want to build a harmonic current meter for power supply testing,I use AD converter to sample AC input current ,but how can i calculate harmonic current ? what is the formulate? how to use FFT?

 

[flatulent]

I have seen a hardware version of this with a notch filter at the main frequency and high pass and low pass filters as well. The output was amplified and rectified. The source of the signal was from a clamp on current transformer.

I suspect that you could do the same thing in DSP.

 

[alphi]

Thank you!
But I need to known how to calculate harmonic current from sampled data.

 

[H_u_n_t_e_r]

You can use switch capasitor filter and scan your frequency band..maxim has that chips(max 8 order) but these chips has 20Khz BW.