Averaging accelerometers

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


Thank You, I’ll have a lot of fun reading these tonight :slightly_smiling_face:

Also if anyone wants to try it out right now you can get theseon sale, they’re like 80 cents right now. I’m also going to try and get some soon.

After doing some rough calculations, you’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). That’s on par with the MPU-9250, which had specs of 300uG/sqrt(hz).

The ISM330DHCX datasheet indicates it’s typical “Acceleration noise density in high-performance mode” is 60ug/sqrt(hz)

There’s another thing to consider:

ADXL345 is a 10-bit sensor (since the noise level spec’d above is .75/bit it’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 that’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. :slight_smile:

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Thank you! That’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 they’re really cheap right now. Thanks!

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

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Thank You!