FFT intricacies

Hello guys,

I've tried to do a little FFT. I created a sinus signal with 10 Hz perisodicity, but both, FFT and CFFT, return a different frequency. There must be some basic problem with my setup, but I can't figure it out.

I's appreciate any clue

Raiko

P.S. I'm using MC 15 on a Win7 machine