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Accelerometer 3D range

accelerometer 3D accelerometer adxl345

Best Answer Dan T, 28 March 2013 - 02:37 AM

From the analog.com web site:

 

User-selectable resolution

  • Fixed 10-bit resolution
  • Full resolution, where resolution increases with g range, up to 13-bit resolution at ±16 g (maintaining 4 mg/LSB scale factor in all g ranges)

Looks like you're in the "Full resolution" mode, so the codes per g (or codes per given tilt angle) does not change, you just tack on extra MSBs.  In other words, below 2g's all 4 ranges look/act identical.  The behavior you were expecting is also available in this other "Fixed 10-bit resolution" mode. But using the 10-bit mode is just throwing away LSBs in 3 of the 4 range settings.

 

I'd stick with the ±16 g range.  B)

 

Then drive around the Boston area and map out all the 16 g potholes for me.  :o

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#1 clefranc

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Posted 28 March 2013 - 12:33 AM

Hi, I'm using an ADXL345 for tilt sensing, to ultimately monitor road roughness with the use of a GPS. The sensor have 4 range, 2, 4, 8 and 16g. I'm sure I misunderstand the range setting, because switching from 2 to 16g always outputs the same values when tilting the device. What should I expect as values for the range setting? Christian



#2 Dan T

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Posted 28 March 2013 - 02:37 AM   Best Answer

From the analog.com web site:

 

User-selectable resolution

  • Fixed 10-bit resolution
  • Full resolution, where resolution increases with g range, up to 13-bit resolution at ±16 g (maintaining 4 mg/LSB scale factor in all g ranges)

Looks like you're in the "Full resolution" mode, so the codes per g (or codes per given tilt angle) does not change, you just tack on extra MSBs.  In other words, below 2g's all 4 ranges look/act identical.  The behavior you were expecting is also available in this other "Fixed 10-bit resolution" mode. But using the 10-bit mode is just throwing away LSBs in 3 of the 4 range settings.

 

I'd stick with the ±16 g range.  B)

 

Then drive around the Boston area and map out all the 16 g potholes for me.  :o







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