pradeep8 0 Report post Posted July 5, 2017 Dear SIr, I am doing the vibration analysis for motor , we done both experimental and Simulation also, I have Time domain data from Experiment Just i need to Import those time data in to my Hypergraph then i will do FFT in Hypergraph. But My problem is 1. The FFT results From Experiment is different from Hypergraph results, 2. In experiment FFT i am getting amplitude as 3000Mm/s2 but in Hyper graph the frequency is same but the amplitude is 6E5, Please can anybody clarify my doubt if you need then i will send the experiment excel also. Here i am attaching Time to frequency conversion Document from Hypergraph Time_to_Freq.pdf (2) (2).pdf Quote Share this post Link to post Share on other sites

Rahul R 329 Report post Posted July 11, 2017 There will be a change in amplitude b/w the time domain and the FFT signal. This is because, a simple sine curve in time domain is represented as Y = A sin (wt), where, A > Amplitude, T > Time Period of oscillations w > 2* PI / T and f = 1/T So, when converting the above curve to frequency domain the equation becomes : Y = A sin (2*PI*F) T This equation is true for a single frequency in which case the amplitude will remain same when you convert from time to frequency. But, when you have a complex response curve with multiple frequencies at different time period, the equation will be similar to the one below : Y = A1 Sin (w1 t1) + A2 Sin ( w2 t2 ) + A3 Sin (w3 t3) + ....+... In the above equation, since the Amplitude is distributed over different frequencies and hence the amplitude of the resulting curve in the frequency domain changes. To cross check this you can do an inverse FFT (IFFT) on the resulted FFT curve to get the original curve. I hope this clarifies your query, Quote Share this post Link to post Share on other sites

pradeep8 0 Report post Posted July 12, 2017 Thanks for your Reply,, Sir, Actually my problem is, for my project we did experiment and we got time data csv file, and from experiment they gave FFT Coversion data (image) also , Just i need to import that csv to our Hypergraph and then i need to Convert Time data to Frequency domain in Hypergraph as per above attachment, My problems. 1. In experiment they got 3m/s2 amplitude for same frequency but for the same data in hypergraph i am getting 2e5 m/s2 but frequency is same for all ,only changes in amplitude, Quote Share this post Link to post Share on other sites

Guest Report post Posted July 18, 2017 Hi Pradeep, Can you check if there are any modelling issues and also check the unit system consistency. Quote Share this post Link to post Share on other sites

pradeep8 0 Report post Posted July 24, 2017 Hi, I got this excel data directly from experimental software (DEWE soft) , just i imported that excel data and converted there time data in to frequency domain, but from dewesoft FFT results, and Hypergrapgh FFT is not matching? Quote Share this post Link to post Share on other sites