Hello,
I am trying to do a very specific measurement that, I believe, should be very straightforward. I am trying to measure the voltage from a photodetector from a laser hitting the back of a reflective Atomic Force Cantilever where the resonant frequency is around 30kHz. The detector voltage signal V(t) is captured using a National Instruments PCI 6251 at 1MB sampling rate and 10MB # of samples. My VI makes use of the DAC Assistant to acquire the signal and run the data through the "convert from dynamic data" to the VI express "Spectral Measurements". I take the Power Spectral Density of the signal but it is still noisy (I understand I need to average a decent amount of signals) and I see other peaks that I don't expect to be there. When I used an oscilloscope I could see a peak that I wanted after averaging many FFT signals.
I am not sure what to do at this point. From the literature it seems pretty straight forward to do this but I am unable to do this effectively. When I tried averaging the signal in Labview it didn't change the spectra. Do I need to store the PSD of each as an array (or as anything else) and compute the average of the stored data that can be plotted? Maybe I should do some filtering if Aliasing is a problem? I am new to labview and have been trying to understand the how to use it effectively but it has been very difficult.
Any help would be greatly appreciated
