For the IIS3dWB ODR and sampling rate...

[ESpen.1]

I need to confirm what the ODR represents - the default ODR is 26667Hz. But what is the actual internal sample rate pre anti-aliasing filter (which must be implemented internally)?

Assuming the actual Fsample is at least 26667, then ODR simply represents the output data rate with respect to additional bandwidth filtering - correct?

To calculate the data parameters for implementation of an FFT, which figure do I use - 26667 or ODR? For example:

Is Delta-F (spectral resolution) = 26667 / N pts always, regardless of ODR?

Similarly, is sample period (Ts) = 1/26667 always, regardless of ODR?

[Eleon BORLINI · Accepted solution]

Hi @ESpen.1​ ,

the internal sample rate is of course > 26.7kHz, and is a multiple of this number, since the frequency is typically divided in a clock tree structure.

This value coincides with the output data rate, or ODR, in the single axis mode for one axis, and in the three axis mode for three axis.

The internal sampling frequency doesn't matter in terms of FFT operation on the data signal. If you want to generate an FFT from the data, you have to consider a 1/ODR time base so basically the answer to your questions:

>> Is Delta-F (spectral resolution) = 26667 / N pts always, regardless of ODR?

>> Similarly, is sample period (Ts) = 1/26667 always, regardless of ODR?

Is positive.

Consider please also that the flatness of the frequency is guaranteed up to about 7kHz (see datasheet, p.19), since this is the f0 of the MEMS structure:

 

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-Eleon

[ESpen.1]

Thank you Eleon...