is my fft code is correct ?

I am trying to find the dominent ferquincy of my current data .

so this is the plot of my current via time :

clc;clear all;

    ADC_data_lim17_GAIN25=load('Data_Lim_17_GAIN_25');
    dec_limit=17 %% decimal limit 
    f_RD_not=892.858e3; %% ferquincy of the RD_not 
    normalization_coffient=(19.6e-3)/(25*15e-3) %% normalization coffient ,that is used to transfer from decimal limit to real current. 
    real_data_ADC=ADC_data_lim17_GAIN25.real_data_ADC; %% dicmal value of the I_1 current (ADC data).
    I_real=real_data_ADC*normalization_coffient; %%real current after considartion of the normalization_coffient.
    real_data_comperator_output=ADC_data_lim17_GAIN25.real_data_IN_driver; %% output of the comperator in the FPGA . 
    t=(1/f_RD_not)*(1:length(real_data_comperator_output)); %% time after normalization using the normalization_coffient. 
    figure(52);
    plot(t,I_real,' red -- d ','linewidth',1);  %% plot--> of I_real 
    hold on ;   
    plot(t,1*dec_limit*normalization_coffient*ones(size(t)),' black ','linewidth',3);  %% plot--> of boundery limit  
    hold on ;
    min_y_of_switch=min(real_data_ADC(length(t)/2:end)); %% used to normal the switch in the steady state. 
    max_y_of_switch=max(real_data_ADC(length(t)/2:end));%% used to normal the switch in the steady state.
    line=(max_y_of_switch-min_y_of_switch); %% coffient for the normlaztion of the comperator output.
%     plot(t,min(I_real(length(t)/2:end))+line*normalization_coffient*real_data_comperator_output,' blue -- O ','linewidth',1);%% plot--> comperator output
    
    title(['  I_1(t) from ADC , Boundery Limit Current=' num2str(dec_limit*normalization_coffient) '[A]']);
    ylabel('I[A]');xlabel('time[ mSec]');grid on;grid minor;
    legend_1=legend ('I_{real}','boundery limit','comperator output'); %% legend 
    set(legend_1,'FontSize',16); %% set the font size of the legend     xlim([ 0 t(end)]);  %% limits of the x axis
    xticks([0:0.0002:t(end)]); %% jumps of X axis 
    ylim([ 0 max(I_real)]);  %% limits of the y axis       
    yticks([ 0:0.1:max(I_real)]); %% jumps of Y axis 
    
     I_real_6=I_real;

and this is my fft of this current code :

figure(2);     
Fs = f_RD_not;            % Sampling frequency                    
T = 1/Fs;             % Sampling period       
L = 2040;             % Length of signal
t_fft = (0:L-1)*T;        % Time vector  
Y = fft(I_real_6);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);     
f = Fs*(0:(L/2))/L;
plot(f,P1); 
title('Single-Sided Amplitude Spectrum of I_1(t) from ADC ')
xlabel('f (K Hz)');
ylabel('|P1(f)|') ;
set(gca,'FontSize',12);grid on; %% font size of the lablels 
ax = gca; %% used to make xlabel as 10^-3
ax.XAxis.Exponent = +3;  %% used to make xlabel as 10^-3
xticks([0:10e3:f(end)]); %% jumps of X axis 

down belew I attached pics of the current in time domain and the same current in ferquncy domain, also I attached the data file .

Is my FFT code is right ? and my domiment ferquncy is 87.97[K Hz] ?

[David Goodmanson]

Hi tomer,

by eye, 17 cycles / 0.2 ms = 85 kHz ok

and the amplitude in the frequency domain also looks good.