Dear Atreya Danturthi , I am glad you read this article as I wrote it !

X² and the weighted X² are two different parameters and cannot really be compared.

Generally, I use X²/|Z|² as a minimization parameter (ie Weight: |Z|² in Fig. 4 of the article) when I am more interested in the results with larger values of impedance. Using X²/|Z|² ensures that the points with large impedance values are better fitted.

If you focus on low impedance values (generally high frequency) then it is better to use non weighted X² as a minimization parameter.

You will see that whether you choose as a minimization parameter X² or X²/|Z|², both values (as well as X/sqrt(N) ) are given. It is better to use the value of the paramter chosen for the minimization.

Also, a more generic comment is that X² or X²/|Z|² can be used to know which equivalent circuit is more adequate. It is less common to use these parameters to compare two sets of data.

I hope it is all clear, and if it is not, let me know.

Best, Nicolas

You can use the measurement model developed by Mark Orazem and co-workers... It is available for free (check his Google Scholar profile, you will find the download link+the user's manual.

Dear Atreya Danturthi , I would like to correct myself.

When you are using X²/|Z|², it means that the X² is weighted by 1/|Z|². Hence the points with lower impedance modulus, that is to say higher frequencies, will weigh more and will be better fitted.

If you want to better fit points with higher modulus, at lower frequencies, you should choose X².

So this is the opposite to what I said earlier.

To sum up:

. X²/Z² -> better fit low modulus points = high frequencies

. X²-> better fit high modulus points = low frequencies

My apologies...

Best regards,

Nicolas

i have a EIS data from 50 kHz to 5 MHz ,do you mean i must use x^2/z^2 for this??