Non-Stationary Data & Fourier Transform

EmptyC

I am trying to transform some non-stationary data into the frequency domain to see if there are any under lying frequencies in the data. a sample of the data can be seen here:

Example 1
Example 2
Example 3

when i look at the data i see a "step" function. I don't know if the fourier transform is the way to go... and was wondering if there was a better transfom to use?

Mt