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enter image description hereThese are my setting that I can adjust and I need to measure 36 Hz. +- 1 Hz. What settings do you recommend?enter image description here

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  • $\begingroup$ Can you change the sampling rate? $\endgroup$ – AlexTP Jun 14 at 10:54
  • $\begingroup$ It tells you your resolution! With the 64 bins selected in your dialog, you don't get better resolution than 125 Hz. So, select the size that gives you enough frequency resolution for your application (which we honestly don't know ;) ). It looks like (Hilmar is 100% on point there) that the FFT is simply not the right tool for your job. What is your job? Can you explain that in more detail? $\endgroup$ – Marcus Müller Jun 14 at 11:49
  • $\begingroup$ I can change the sample rate but 8k is as low as I can go. $\endgroup$ – Jordan Hancock Jun 14 at 12:00
  • $\begingroup$ I’m trying to replace an old gates tension meter with a generic app off the google pay store. $\endgroup$ – Jordan Hancock Jun 14 at 12:02
  • $\begingroup$ There simply isn't enough detail. What sensor are you using? How is it mechanically connected to the belt? What is the response of the sensor to belt tension? How is the sensor coupled into the phone? What is this "generic Google Pay store" app? Please edit your question to include this information. $\endgroup$ – TimWescott Jun 14 at 17:46
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At 8kHz sample rate, an 8192 point FFT would give you about 1 Hz resolution. In order to reduce spectral leakage you may want to go larger than this but this will also make it very slow.

Depending on your application, it may be a lot easier to just use a time domain bandpass filter.

Since your sample rate is way higher than your frequency range of interest you could also consider down-sampling to reduce computational complexity.

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  • $\begingroup$ Awesome thanks, How could the transform interval and decimations help too? $\endgroup$ – Jordan Hancock Jun 14 at 12:10
  • $\begingroup$ Why don't just do a bandpass instead. FFT is harder than most people think it is, so don't use it until you have to or you have invested enough in understanding the non-trivial math behind it. $\endgroup$ – Hilmar Jun 15 at 13:09

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