I have ZsimDemo installed to fit impedance data. But I can't  import data. I have my original data in excel and then I have them in .txt format also. But when I try to import txt file data , it gives an error '' you have only 1 data points''. but I have 100 data points. 1st column with frequency and 2nd column with Impedance magnitude. Is there any special format of data file?

I appreciate if somebody can help me.