How to locate exact frequency of peak in FFT spectrum

[@demohmand]

Great video once again! Thank you for sharing

[@sabrinamekhoukh]

Hello, Please, for the calculation of the shaft rotation frequency (f=RPM/60) do we take the rotation speed indicated on the nameplate or do we measure the speed on the spot during the collection of vibrations data's. In this case the rotation speed will be variable every time when we collect data and Wich tachymeter do you recommend. Thanks to anyone who can help me to clarify this point

[@AdashCompany]

To measure speed during taking of vibration data will be more precise. Of course to trend the vibration data it is good to measure the machine under same speed and load. We are using laser speed probe with reflective tape glued on the shaft.

[@kamalmanzukie]

it's like interpolation? you can also calculate it from the phase difference between frames

[@AdashCompany]

Yes, it is like interpolation.

[@AlphatecEngineering]

Great info folks! thanks for sharing it.

[@NicosLeben]

Okay, but how to I calculate the exact frequency by myself if I do not have this software but only the result of the fourier transformation?

[@AdashCompany]

First, we find a peak in the spectrum which we are interested in. Then we take higher adjacent peak of that peak. Thus, we have two adjacent spectral lines (f1, y1) and (f1 + df, y2). If the spectrum has been calculated after using Hanning window, the frequency correction can be performed using this equation: f = f1 + df * (2 * y2 - y1) / (y1 + y2), where f is the corrected signal frequency f1 is the frequency of left line of my lines pair y1 is amplitude on f1 y2 is amplitude on f1 + df df is delta frequency between two lines

[@jacobwood8653]

@@AdashCompany is there a similar equation for amplitude ??

[@jacobwood8653]

and phase?

[@AdashCompany]

​@@jacobwood8653 It can be deduced for amplitude.

[@AdashCompany]

​@@jacobwood8653 We are not sure about it at the moment. This would need to be studied. Maybe this is question for Google ;-)

[@shaikhminhajahmed6761]

Thanks for your knowledge sharing