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frequency vs magnitude of continous sine wave

im using the signal simulator to generate a continous sine signal and i want to get the frequency response of this signal, apparently working on the samples each itteration doenst work as it doesnt give correct values for neither magnitudes nor frequencies so i gussed that i needed to append the signal and work on it after the loop is terminated , it gave peaks at the correct frequencies i used in the signal simulator however the magnitudes were not correct im usign the spectral express vi with (magnitude- peak) as configuration so for example i run the vi generating a sine wave of 5hz and amplitude 5 for a certain time and then shfit to 10HZ with same amplitude and then stop the loop the graph will have 2 peaks at 5 and 10 HZ but the magnitude is incorrect. the thing is the signal simulator will be replaced with a daq assistant aquiring analog acceleration at the same sampling rate and number of samples so i need help with why the magnitudes are not correct so i can work with the accelerometer, the vi is attached.

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Message 1 of 7
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You are generating 50000 samples/second at 10.1 Hz, but are only looking at 1000 samples at a time, that's not even a full wave. You cannot get a frequency out of a single set.

 

If the frequency changes over time, a global FFT is ill advised. Maybe you should do a jtfa or wavelet analysis or similar.

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Message 2 of 7
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are there any similar examples to what i want to do coz i barely know how to use labview 

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Message 3 of 7
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@peterRFA wrote:

are there any similar examples to what i want to do coz i barely know how to use labview 


And express VIs are barely LabVIEW. 😄

 

Do you have the advanced signal processing toolkit?

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Message 4 of 7
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yes i do

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also i have sound and vibration if it helps

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Message 6 of 7
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So look at some of the examples....

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