# Calculating the magnitude of impedance

I am working on a project to model the electrical characteristics of a piezoelectric (PZT) and would like to get a sanity check to make sure I am going about it in a way that makes sense.

So I am using the Van Dyke-Butterworth model for a PZT. I have measured the absolute impedance of the PZT using an impedance analyzer and am now working to fit the impedance function for the Van Dyke-Butterworth model to my data to find the value of the model components.

Where I need a check is for the steps of calculating the magnitude of the impedance. 1 write down Z [2] multiply the numerator and denominator by the complex conjugate of the denominator [3] separate into real and imaginary parts and square them [4] take the square root

I want to make sure I am not adding any terms because the steps seem to make sense but I am ending up with values extremely different for my calculated abs(Z) than from my measured abs(Z).

Am I missing something obvious? Any thoughts would be most appreciated

• I found an answer to my own question over on the math Stack Exchange
– prov
Oct 21, 2017 at 16:39