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Just looking for advise on the best way to measure superimposed frequencies on my raw data. The raw data (voltage versus time) is ultimately a noisy sine wave with a frequency of 1Hz. I need to determine where the noise is coming from, i.e. is it vibrational, electrical or surrounding noise, hence requiring the frequency of the noise if possible.
Any advise on the best way of filtering the data would be appreciated. Currently I am using a butterworth filter with a cutoff setting of 1.5Hz. The original data was sampled at 1.5KHz so the noise was measured and so could be filtered during postprocessing.
Also when filtering I don't want to loose important data i.e. sudden peaks or drops.
Have you tried spectrum analysis of your data? That will give you the frequency content of the signal plus noise. One peak will be at the 1 Hz sine signal and other peaks will correspond with the supeimposed signals. With a 1.5 kHz sampling rate you would get information on frequency content up to the Nyquist frequency of 750 Hz. A peak at 50 or 60 Hz will likely be power line frequency interference. Gears, bearings, and motor armature slots produce characteristic frequencies which are related to the rotational speed.
I don't have LV 6.1 but in 6.0 there are several. Look at Functions>>Analyze>>Waveform Measurements and Functions>>Analyze>>Signal Processing>>Frequency Domain. The help files are very useful in understanding these VIs if you are not a signal processing expert.
