Spectral Analysis - extracting phase
Hello, i have maybe same problem like Nick. I need to determinate phase shift between two signals from accelerometers on vibration. I have DEWE 43 A and basic Dewesoft X2. It is possible determinate with Math and FFT? And if so, how?
Thank you!
Peter
Petr,
It can be done! You need to dig into the complex FFT and array maths functions.
For two vibration channels called vib1 and vib2:
First use the Math FFT functions to set up an FFT of each of your vibration channels selecting "complex" as the output and block history as the caluclation type, as I presume you want the variation of angle vs time. This creates two new channels Vib1/CplxFFT and Vib2/CplxFFT.
Then go into the "formula" functions and find the "complex" tab and you will find "angle". Then you can make a new signal:
AngleVector = angle(Vib1/Cplx)-angle(Vib2/Cplx);
which will be the difference in angle between each spectral line of the two ffts vs frequency ...... and varying with time. you can plot this as a spectrum or a spectrogram to see what's happening.
To get the phase at a single frequency you can use array addressing such that AngleVector(10) will be the 10th spectral line or AngleVector{10} which will be the angle at the nearest spectral line to 10Hz.
When I asked the question the functionality was available but hidden; now the complex and array math functions are there to see and use!
Hello Mark an
I also want to display the phase of a signal. Kindly email the instructions for my 43a with X2 software.
.Regards mike
Hello nick
I also want to display the phase of a signal. Kindly email the instructions for my 43a with X2 software.
.Regards mike
I also have a 43a with X2 software and want to export amplitude and phase of a signal.
Kindly email the instructions
Many thanks
Mike
I also have a 43a with X2 software and want to export amplitude and phase of a signal.
Kindly email the instructions
Many thanks
Mike
Hi Mike,
.. the answer is actually in my post of 8th Sept 2015.
==============================================================================
For two vibration channels called vib1 and vib2:
First use the Math FFT functions to set up an FFT of each of your vibration channels selecting "complex" as the output and block history as the calculation type, as I presume you want the variation of angle vs time. This creates two new channels Vib1/CplxFFT and Vib2/CplxFFT.
Then go into the "formula" functions and find the "complex" tab and you will find "angle". Then you can make a new signal:
AngleVector = angle(Vib1/Cplx)-angle(Vib2/Cplx);
which will be the difference in angle between each spectral line of the two ffts vs frequency ...... and varying with time. you can plot this as a spectrum or a spectrogram to see what's happening.
To get the phase at a single frequency you can use array addressing such that AngleVector(10) will be the 10th spectral line or AngleVector{10} which will be the angle at the nearest spectral line to 10Hz.
==============================================================================
Our friends in Slovenia make it very easy!
I've attached an example setup file to this post .. as I've lost your mail address & phone number.
all best,
Nick
Attached files: