Good day, how can I compare the Sensitivity of ADXL355 and 345 in terms of
detecting low vibrations or microvibration? How can I compare their given
values of LSB/g to determine what accelerometer better suit the design for
Thank you for your post. If I understand your question correctly, you are trying to determine which sensor has better capability, with respect to being able to detect vibrations, which have small magnitudes. Is that a fair interpretation? The following article would define that as the "resolution" of the sensor.
MEMS Vibration Monitoring: From Acceleration to Velocity | Analog Devices
This article proposes that noise is one of the most influential behaviors, when it comes to estimating the resolution of a sensor. If we assume that both sensors have sufficient bandwidth and measurement ranges for your application, let's focus on developing a simple comparison metric, based on Noise Density. Noise Density describes the energy of the noise, with respect to a particular bandwidth. The ADXL355 datasheet directly specifies a Noise Density of 25ug/sqrt(Hz), in Table 1 (page 4, Rev 0).
The ADXL345 Datasheet specifies Total Noise of 0.75 LSBrms, for an ODR of 100Hz, in Table 1 (page 5, Rev E).
The ADXL345 Datasheet also specifies that 1g = 256LSB, for the +/-2g range and 10-bits of resolution, in Table 1 (page 5, Rev E).
Convert the total noise specification (from the ADXL345 datasheet) into the units (micro-g = ug) that are used in the ADXL355's datasheet:
If assume that the noise bandwidth is equal to 1/2 of the ORD, we can estimate the equivalent noise density of the ADXL345 to be:
Based on this estimation, we can say that the ADXL355 noise is over 16x better than that of the ADXL345. If we assume that this is the key limit, the ADXL355 is clearly superior to the ADXL345 for "detecting low level vibrations."
Does that help?
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