# How to find proper frequency peaks within a frequency spectrum?

3 views (last 30 days)
Zafer Duyenli on 18 Dec 2022
Commented: Mathieu NOE on 19 Dec 2022
Hello there,
I am trying to detect any mechanical issues these require maintenance by observing the feature's frequency spectrums created via data taken from accelerometer calculations which are made axial and radial (saved as .mat). I have to measure peak frequencies properly by using the code given by my instructor -he also insisted that I am obliged to use the code as it is- in order to get an idea about the condition of the system but I can't make programatical data tips that automatically detects peak frequencies in a reasonable threshold and margin. How can I get those data tips? My code is shown below, thank you for your time already.
clc
clear
x=BR; %%%%%%Data file name
sp=fft(x);
nn=length(x);
sp(1:2)=zeros(size(1:2));
sp(nn-1:nn)=zeros(size(1:2));
x=real(ifft(sp));
fss=5000;
T=1/fss;
upfreq=fss/2;
p1=length(x);
z=(2/p1)*abs(fft(x));
z=z(1:p1/2-1);
z(1,1)=0.5*z(1,1);
nff=length(z);
nf1=round(2*nff*upfreq/fss);
z=z(1:nf1);
freqspec=plot((0:nf1-1).*(fss/p1),abs(z)),
freqspec =
Line with properties: Color: [0 0.4470 0.7410] LineStyle: '-' LineWidth: 0.5000 Marker: 'none' MarkerSize: 6 MarkerFaceColor: 'none' XData: [0 0.1163 0.2325 0.3488 0.4650 0.5813 0.6975 0.8138 0.9301 1.0463 1.1626 1.2788 1.3951 1.5113 1.6276 1.7439 1.8601 1.9764 2.0926 2.2089 2.3251 2.4414 2.5577 2.6739 2.7902 2.9064 3.0227 3.1390 3.2552 3.3715 3.4877 3.6040 3.7202 … ] YData: [0 1.4019e-18 0.0011 5.5658e-04 3.8345e-04 4.5997e-04 0.0019 0.0036 0.0020 9.3827e-04 3.8793e-04 0.0013 0.0024 0.0032 0.0012 6.2368e-04 0.0020 9.6836e-04 7.2553e-04 4.0302e-04 8.8694e-04 0.0016 0.0011 0.0030 4.2645e-04 5.2585e-04 … ] Show all properties
set(gca,'FontSize',10), xlabel('Frequency (Hz)'),ylabel('Amplitude')
axis([0 2500 0 0.05])
zoom on
Mathieu NOE on 19 Dec 2022
hello
look for findpeaks
you can also use text to create annotations inside the figure, once you know the x, y coordnates of the selected peaks

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