I have uploaded the code to the APM. The board is on a flat and stable surface. When I start the serial monitor I will receive a high accel Z, as you can see here.




Is there anything wrong?


If not can it be calibrated?



Scott Quartochi


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Thanks to Jani Hirvinen for this_____

Well Z-accel is never at zero when quad stays on table :)

It should show around 460 when at level. Why? Answer is rather simple. It's due earth gravity. Accell measures gravity changes and when It is level and not moving x/y axis are at zero but due earth is pulling us towards it's center with aproximate force of 1G. Accell what we use on OilPan shows 460 at 1G. This walue changes a bit on different locations. Best way to find it is to calibrate x/y to zero and then told you quad 90 degrees. And you should see 460ish value on your X or Y axis depends on which way you tilted IMU.

So after that you can make Z calibration correctly :)
Certainly Jani is right that an accelerometer should show a nonzero value for the z-axis because of earth gravity. I am curious about the actual numbers reported though from the ADC. Clearly none of the accelerations in Scotts original post are zero or 460. Is it correct that the ADC reports 2048 for an actual value of zero (I am guessing based on the fact that the ACD is 12-bit), and that the scaling would then be about 47 counts/mps2 (backing out from the statment that 460 translates to 1G=9.8mps2)?
Presumbly these are things written down somewhere... can someone point me to the location where I should find the documentation necessary to interpret these values from the OilPan?

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