Phase difference

[Petar2015]

Hi,

I'd like to plot phase difference between two signal(input-output), the method which I'm using currently, is taking "FFT" and (r-teta)....and subtracting the phases, but what I obtain isn't so desirable, Do you know anyother option or suggestion to make my results better?

I've attached the plot and marked them, one of the is "Output FFT- magnitiude vs. Frequency" as you see it's acceptable, but another which is "phase difference vs. freq" isn't so good.:(

Thanks

Petar

[johnsold]

This does not seem to be a Signal Conditioning issue. You would probably get more responses if you post in the LabVIEW Board.

We really cannot see the scales on the plots and, more importantly, we cannot see the actual data. Please save some typical data as default values and post your VI.

If either the input or output signal is very noisy, it may be difficult to define or measure a phase difference.

Lynn

[Henrik_Volkers]

Some code and data really would be helpful......

Take a look at the FRF examples.....

two points: 

use a phaseunwrap after calculating the difference AND

include a basic groupdelay for your (response) signal either in the time or frequency domain....

[Rscd27]

As they said if you provide more information maybe we will be able to help you

[Petar2015]

Thanks for your replies, I've attached the acquired data..

(notepad file).1 column: Frequency......2nd column (FRF of output- magnitude)...........3rd column(FRF phase difference(output-input)).

In the figure: left column: input....FRF magnitude.................right column: output...phase frf....fft of output in every step.

thanks

Petar

[Rscd27]

Can you gives the whole project. It says i have some SubVIs missing.

[Henrik_Volkers · Accepted solution]

here is a short play around with  phase unwrap a groupdelay of >1s ????

What and how are you measuring????

Can't open your code... still stick to an old version here

[Petar2015]

Thnaks so much indeed! It's exactely what I want!!! I'm so excited...

Would you please let me know how can I send the whole project? I tried "Save all" but its the same file again.

Thanks

Petar

[Rscd27]

You have to save the whole project in a .rar or .zip file. I will be waiting for the code.

[Petar2015]

when I save it as "rar", it can't be attached, I face an error