You are close to what a waveform analyzer does. It is not mathematically very clean, but it is useful for watching frequency evolution over time. But you need a time averaging buffer. For each of the 6 segments, do an FFT and get the Mag and phase. Have a buffer that is the same length as your phase and magnitude and as each segment is acquired (B is buffer and N is new signal)
B' = x*B + (1-x)*N This gives a time average. Where the time constant x goes from 0 to 1. If X is zero, then you are only looking at the new signal. If x is 1 then you are only looking at the past. Usually it is expressed as a Number to average as an exponential average. But this way you can update the average in real time. BTW, this is hardly a windows question! The math involved in FFT is mostly platform independent! :-) -Scott At 15:50 +0100 02/03/2004, Roman Golubovski wrote: >I need help/guidance on how to use "FFT Spectrum (Mag-Phase).vi" to perform >RMS averaging on sampled strip(s). DAQ produces strip of up to 120.000 >samples (max 120sec at max 1kS/s). After that I am asked to do the following: > >1) segment the strip into overlaping segments (equally sized) >2) perform RMS averaging on them > >I am not familiar with this particular technological background and the >"customer" also cannot explain how it is being done - he just wants me to >perform what his signal analyzer does! I am not even sure the segmentation >is compatible with the RMS averaging process. > >Anyway, lets assume the strip length is 200 samples, the egment size is 40 >samples and the overlap is 10 samples. Than obviously I can segment the >strip into 6 segments starting at strip positions 0, 29,59,89,119,159. > >What do I do now? I gues I have to turn the segments into waveforms with >dt=1/fs and t0=0? I guess I should put the "FFT Spectrum (Mag-Phase).vi" in >a loop with 6 iterations feeding a segment-waveform into the "time signal" >connector each iteration? I expect the output is NOT auto-indexed? > >How to apply it properly actually?
