The output unit of pwelch function
2 views (last 30 days)
Show older comments
Hi,
I need to clarify the output unit of the function pwelch. The help says the output is psd. Could someone please help me clarify my understanding of the unit of this psd?
First about the function fft. Using the MatLab example:
...
NFFT = 2^nextpow2(L); % Next power of 2 from length of y
Y = fft(y,NFFT)/L;
...
effectively it is a DFT (right?). So:
1). If y has a velocity unit m/s, what should be the unit of 2*abs(Y(1:NFFT/2+1))? Is it (m/s)/Hz(=m) ?
2). If this is correct, then if I need a energy like output, then what I need is the term 2*(abs(Y(1:NFFT/2+1))).^2, am I right?
Now about the pwelch function:
Say I run the following command:
...
[pxx,f]=pwelch(y,hanning(segsz),ovp*segsz,segsz,Fs);
...
where segsz=NFFT/4 and Fs=1000 (1000Hz sample rate),
3) what is the unit of pxx? Is it (m/s)/Hz or (m/s)^2/Hz(=m^2/s)
Many thanks for your help!
Liam
0 Comments
Answers (0)
See Also
Categories
Find more on Parametric Spectral Estimation in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!