Dear all,
I would like to perform an online and offline FFT analysis on accelerometer data that I have acquired.
I would be acquiring the data for quite a few hours. So I have decided to save the file in the TDMS file format.
I have no issue with recording the waveform and FFT spectrum.
The main problem that I am having is the offline post processing. That said, I made a simple VI to try out the zoom FFT. It seems to work fine for performing FFT on waveform of duration longer than 1second. However, when I would like to have the FFT of just a 1second slice of the entire recording, there is no FFT spectrum available for viewing. I am not sure if it is only me or am I doing things wrongly.
I've attached the recording VI and playback VI.
A separate question is whether the VI that I did is actually doing what I want. For real time processing of data, from what I understand of FFT, it is that we are actually acquiring data at say 1000 samples and the data is being past into the FFT to generate a spectrum for that particular 1000 samples. Whether it is averaged or not, depends on the averaging parameter that we input into the FFT. If we do post processing on data that is logged for say 100 seconds, and we want to have the RMS averaged of the first 20 seconds or so, is it correct to say that we just have to wire in the recorded waveform of the first 20 seconds into the data input terminal and set the averaging to RMS averaging?
If I had acquired a longer duration of waveform (say 24 hrs) and I want the RMS average of the waveform. Is is possible to actually compute it out? I know that it would most likely cause our computers to crash. So I am thinking if it is alright to take the RMS average of say the last hour of the waveform to compute the RMS average of the waveform to give the estimate of the 24 hour duration waveform.
Much appreciated for the kind assistance to any kind souls answering my fundamental questions.