STEVAL-BFA001V1B FFT results

[BSR]

Hello Sir/Madam,

We are validating STEVAL-BFA001V1B on motor for condition monitoring.

Motor is rotating with 1500 RPM speed , when I observe the FFT results , rotating frequency 1X is coming around 26Hz when my settings are ODR- 6660Hz (also with 3330Hz) , FFT-2048 , Hanning filter , time duration 1000mS and overlapping 75%.

26 Hz corresponding to 26* 60 - 1560 RPM , But motor is rotating with 1500 RPM. Why is this variation?

Is this variation is OK for proceed?

[Eleon BORLINI]

Hi @BSR​ , I'm wondering if the discrepancy between 1500 rpm and 1560 rpm can be originated by some approximation errors in the FFT log spacing and/or in the 26Hz rounding (although it seems anyway too much)... since the FR array is composed by 2048 samples, f_max ODR/2 = 3.33kHz, a logarithmic array increase the spacing at higher frequencies... Didi you check if you get same discrepancies at lower ORD (<3.3kHz)?

Btw, how can you be sure that the nominal rpm of your motor are 1500?

Regards