# Averaging accelerometers

Okay, here are some relevant papers:
Bear in mind that combining multiple gyros is the same problem as multiple accelerometers.

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Thank You, Iâll have a lot of fun reading these tonight

Also if anyone wants to try it out right now you can get theseon sale, theyâre like 80 cents right now. Iâm also going to try and get some soon.

After doing some rough calculations, youâll need to average 24 of these chips to equal the accelerometer noise performance of a single ISM330DHCX.

Here are calculations on which that is based:

From ADXL345 Datasheet:

Typical Sensitivity (@2 g, 100Hz): 10-bit resolution 256 LSB/g
Accel Noise: 0.75 LSB rms

So each bit is equal to 1/256 G = 3.9mG. And the X/Y axis noise level is .75 of a bit @100Hz, so the noise is 3.9*.75mG = 2.95mG = 2950uG. Dividing that by square root of 100Hz yields 295 uG/sqrt(hz). Thatâs on par with the MPU-9250, which had specs of 300uG/sqrt(hz).

The ISM330DHCX datasheet indicates itâs typical âAcceleration noise density in high-performance modeâ is 60ug/sqrt(hz)

Thereâs another thing to consider:

ADXL345 is a 10-bit sensor (since the noise level specâd above is .75/bit itâs resolution is less than the noise), ISM330DHCX is 16-bit. 6 bits of resolution is really a huge difference, although of course some of thatâs going to be noise.

I encourage you to review the accelerometer noise density specs carefully if you plan to estimate displacement with them. Getting familiar with the datasheets is a very valuable skill.

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Thank you! Thatâs pretty much what I found, I looked through about 10 accelerometers and the best performance/price was by far the ISM330DHCX. The main reason I posted those was because theyâre really cheap right now. Thanks!

Feel free to stay in touch by personal message if youâd like to discuss more as you continue your research and development.

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Thank You!