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I have ADXL345 digital accelerometer by Analog Devices. I use Beaglebone ADXL345 library that exist here: http://inspire.logicsupply.com/2014/08/beaglebone-3-axis-accelerometer.html

So I can read the accelerations at X,Y,Z axis. However, when I placed the board at plate surface, it reads X and Y accelerations as -0.728G and -0.788G. They should be zero. How to calibrate this accelerometer?

In addition, it reads stable z axis accelaration as 2.044G. It only changes If I reverse the board. I dont understand. What does it mean?

my ADXL345 board:
enter image description here

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  • \$\begingroup\$ That doesn't sound normal and it seems like a reading error of some form. For the Z axis what reading do you get if the board is turned upside down? Are those X & Y readings stable at those values or do they drift around a bit? For those readings it seems something is badly wrong rather than it just needing some calibration. \$\endgroup\$ – PeterJ Apr 20 '15 at 13:50
  • \$\begingroup\$ It is around 1G when I reverse board. X&Y values changes withthe motion there is no problem but not 0 at plate surface. I read values like that i.imgur.com/deewXqM.png \$\endgroup\$ – user38138 Apr 20 '15 at 14:36
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Calibration is really just a case of finding the "zero point" value (which you have identified) and subtracting that from any future readings.

That's basically all there is to it. Sit the unit on a stable flat surface, take a number of readings, create an average of them, and use that as an offset value to apply to all your future readings.

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