Hi all,
I kundly ask about the effective resolution for this accelerometer model.
Suppose to work ad ODR=400 Hz hence BW=200 Hz.
From the device datasheet we have a PSD=99 ug/sqrt(Hz) @ 4g scale ODR=400 Hz
From the AN4075 the SNR(db) will be equal to:
SNR(db)=20*log*(4g/(2sqrt(2)) / NRMS)
where:
NRMS = PSD*SQRT(BW)=99u*SQRT(200)=1.4 mg
Hence:
SNR(db)=60.087 dB
and finally we have for the bits number:
n=(SNR(dB)-1.76)/6.02=9.68 bit
This means that instead of the theoretical 14 bit we have really usable 9 bit of resolution then 4g/2^9.68=4.87 mg of resolution.
Someone have carried out similar calculation?
Thanks in advance!
Best regards
Fabio
已解决! 转到解答。

Hi Fabio,
The number of effective bits and typical noise calculated in mg RMS is actually given in tables 3, 4, 5 and 6 of the AN4075 for all possible ODR/MODS/LNOISE combinations. As you can see, it is practically 14-bit true at 1.56Hz in Hi Resolution Mode with the Low Noise bit set. As the sample rate decreases the resolution improves. The best case scenario is 14-bit true at the lowest sample rate.
Best regards,
Tomas

Hi Fabio,
The number of effective bits and typical noise calculated in mg RMS is actually given in tables 3, 4, 5 and 6 of the AN4075 for all possible ODR/MODS/LNOISE combinations. As you can see, it is practically 14-bit true at 1.56Hz in Hi Resolution Mode with the Low Noise bit set. As the sample rate decreases the resolution improves. The best case scenario is 14-bit true at the lowest sample rate.
Best regards,
Tomas
