Need Accelerometer Recommendation - Adafruit MMA8451 Accelerometer Breakout

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jackcchen1
 
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Joined: Mon Jul 11, 2022 12:42 pm

Need Accelerometer Recommendation - Adafruit MMA8451 Accelerometer Breakout

Post by jackcchen1 »

Hi Everyone!

I am considering using the "Adafruit Triple-Axis Accelerometer - ±2/4/8g @ 14-bit - MMA8451" (https://www.adafruit.com/product/2019) for a classroom project to measure small changes in the acceleration of gravity, g = 9.81 m/s^2, but I'm unsure about the precision of the measurements this device can provide.

Section 3.1 of the datasheet for this accelerometer (https://cdn-shop.adafruit.com/datasheets/MMA8451Q-1.pdf) suggests that "In 2g mode the sensitivity is 4096 counts/g."

1) Can someone confirm that this means that the smallest change in acceleration that this device can measure is approximately:
(9.81 m/s^2)/4096 = 0.0024 m/s^2 ?

2) Also, can someone recommend an accelerometer that might be able to provide more precise measurements?

TIA,
Jack

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sj_remington
 
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Joined: Mon Jul 27, 2020 4:51 pm

Re: Need Accelerometer Recommendation - Adafruit MMA8451 Accelerometer Breakout

Post by sj_remington »

There are several issues that limit the lowest reliably detectable change in a measurement: the number of significant bits in the measurement result, the temperature sensitivity of the sensor gain (full scale setting), the inherent device noise, changes in the local environment (temperature drift, vibrations), the measurement bandwidth you set and the number of measurements you average.

Some of that information is in the data sheet, but it does take some head scratching, plus detailed knowledge of your measurement environment, to sort it out.

Why do you expect the local value of g to change, and by how much? Once you have settled on a value, look for a sensor that you can expect to detect that change. Since the market is competitive, generally speaking, the more expensive the sensor, the lower the noise and higher the accuracy.

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