Hi

I`m doing some research on sensors for measuring structural vibrations.

Looking into ADXL355 datasheet I found that its Scale Factor is equal to 3.9 ug/LSB using a Dynamic Range of +-2g . Datasheet also informs the noise density is equal to 25 ug/rt(Hz). However, if we use this noise density with a 1000 Hz BW we find that the resolution of the sensor is Resolution = 25u*rt(1000*pi/2) ~ 1mg.

So, does it make sense using a scale factor 250 times lower than the resolution of the sensor? Am I missing something?

If I used ADXL354 that has 20 ug/rt(Hz) noise density, would I be able to get a better resolution?

Thanks.

Thank you for this post. I am having trouble understanding why you are concerned about the scale factor (for each LSB) being much lower than the projected total noise, assuming a noise bandwidth of 1000Hz. Why is that a problem or even surprising? In most signal chains that I have worked on, that was actually desirable. Sure, 250x is a large difference but will every application use a bandwidth of 1000Hz? At 1Hz, that 250x will reduce to ~8x.

With respect to the ADXL354, it would seem like you already have your answer (yes, by virtue of lower noise density), but you will need to preserve that through your signal chain, in order to retain that value.

I hope that this helps!