Hi,
I'm new here and relatively new to signal processing and analysis. My ultimate goal is to find the mode shapes of a system, but I'm currently working on building the FRF before I move into the next stage. When computing H=Sxy/Sxx (cross power spectrum over input spectrum), I'm getting a minimum instead of a maximum magnitude on my frequency vs magnitude graph, while the rest of the FRF is pretty much constant. I applied FFT to both the input and output, and both have their resonant frequencies or spectral line at the expected frequency (2.01 Hz). I assume the magnitude is minimum Since Sxx has a higher magnitude spectral line than Sxy, but I'm told the FRF should show a maximum since the test showed a mode at 2.01 Hz and should obtain the information from there.
What am I not understanding? Or what does it mean to have a minimum at the frequency of interest?
Input is in lbf and output is in g's
I'm new here and relatively new to signal processing and analysis. My ultimate goal is to find the mode shapes of a system, but I'm currently working on building the FRF before I move into the next stage. When computing H=Sxy/Sxx (cross power spectrum over input spectrum), I'm getting a minimum instead of a maximum magnitude on my frequency vs magnitude graph, while the rest of the FRF is pretty much constant. I applied FFT to both the input and output, and both have their resonant frequencies or spectral line at the expected frequency (2.01 Hz). I assume the magnitude is minimum Since Sxx has a higher magnitude spectral line than Sxy, but I'm told the FRF should show a maximum since the test showed a mode at 2.01 Hz and should obtain the information from there.
What am I not understanding? Or what does it mean to have a minimum at the frequency of interest?
Input is in lbf and output is in g's