Frequency detection at the natural frequency.

[EJW2003]

This may sound strange but here goes.  I have a rotating part that has a natural harmonic frequency of 17Hz.  I am trying to do a harmonic analysis on this item to pick up any frequencies that have been induced into the part.  However, sometimes there are frequencies induced that are the same or multiples of the natural harmonics, and i can not see these.  Any suggestions on what i may do hardware or software (Labview 8.5) wise to pick up the induced frequencies?

[_S_G]

Software wise, an FFT should be able to sense all the frequencies in your signal.  There are VIs to do this in the signal analysis palette.

A basic concern is your sampling frequency.  Is it high enough to be able to detect the frequencies you expect to see?  For instance, if your hardware is capable of sampling at 10 Hz, you cannot detect correctly signals that are faster than 5 Hz (Nyquist criterion).  In practice, I try to use sampling frequencies that are atleast 5 or 10 times the maximum frequency I expect to detect.