FFT requirements of real time signal from sensors
Q1: is this a correct setup?

I'm guessing &quot;no&quot; but that really depends on your application and goal. The process will produce numbers but if these numbers are useful or not depends on what you want to do with them.

Q2: is there a minimum requirement for the buffer (FFT window?).

Mathematically speaking : no. You can run a FFT on a single sample if you want to. t doesn't do anything useful but it can be done. The real requirements come from your application.

I have now set it up to process 10 samples. Q3. what is the maximum number of frequencies that can be detected in this scenario?

An FFT setup like this will you give  you ten numbers which are the complex amplitudes from -0.5Hz to +0.5Hz in 0.1 Hz steps. That's not the only frequencies you &quot;detect&quot; but that's a more complicated topic. If you feed a 0.15Hz sine wave in the process all 10 numbers will be non-zero.
You may also get significant aliasing with this setup, if you don't use a decent anti-aliasing filter before the current sensor.