Bandwidth vs ODR

[gabriel.arnautu]

Hi,

I would like to know what is the difference between bandwidth and ODR. I tough that just the analog accelerometers have bandwidth and the digital ones have ODR. For example, IIS3DWB can go up to 5kHz bandwidth and 26.7kHz ODR. Does this means that internally, the accelerometer takes up to 5kHz samples, but it can output them at 26.7kHz rate? If yes, it means that I will have duplicate data if the ODR is greater than 5kHz?

Regards,

Gabriel

[Eleon BORLINI]

Hi @gabriel.arnautu​ , the bandwidth is typically the maximum detectable vibration frequency that the internal mechanical structure of the accelerometer can detect. Imagine the MEMS as a classical oscillating system: the IIS3DWB  cannot detect a signal above 5kHz. On the other side, the ODR is the "capability" of the digital output: the IIS3DWB can output data at a 26.7kHz max rate, but if the frequency you want to detect is above 5kHz you will see only noise, or a very amplitude-reduced signal. But it is not useless having an ODR > BW; you can for example reconstruct your 5kHz or below signal with at leas 26.7k/5k = 5 points. Regards

[gabriel.arnautu]

Thanks @Eleon BORLINI​ ! I don't understand the last part with reconstructing with at least "26.7k/5k = 5 points".

I need to record frequency up to 1.6kHz. I need to do FFT as well for the data, so I will need ODR at least 3.2kHz, right? For this case, a 1.6kHz BW and 3.2kHz ODR should be enough?

Also, I want to record it for more than 16g, but I was not able to find a suitable accelerometer with more than 16g and an ODR with at least 3.2kHz.

Regards,

Gabriel