Alejandro,
There is no built in function in CVI to extract the main tone out of a signal; I suggest that you take the power spectrum of the signal using the AutoPowerSpectrum function; then you can use the PeakDetector function to obtain the main frequency components.
This is a vary basic algorithm, however it is a good start; you can polish it by filtering the data to work only on a specific band that you are interested, remove the DC component or perform some averaging to get a more accurate measurement.
I hopes this helps get you started.
Regards,
Juan Carlos
N.I.
