I am confused as to what the units are for the processed accelerometer data. On pages 65 & 66 of the UM7 datasheet it says under the DREG_ACCEL_PROC_(X,Y,Z) registers that “Contains the actual measured acceleration in m/s/s after calibration has been applied.” However on http://www.chrobotics.com/library/accel-position-velocity in the paragraph right above the Section 3. Estimating Velocity and Position, it says “Note that CH Robotics sensors typically output acceleration in units of gravities, not m/s/s or ft/s/s.”
I am more inclined to believe the website (the processed acceleration is in gravities) because when I plot the processed accelerometer data when the IMU is still, through CHR Serial Interface or MATLAB (after extracting from microprocessor) I get x and y are zero and z is close to 1. The exact numbers are actually x, y and z are -0.01, -0.016 and -0.96 respectively. Nevertheless based on this I am inclined to believe the acceleration is in gravities and not m/s/s.
However I am having issues with distance accuracies when running my algorithms with this data and so I am starting to think that the IMU is actually reporting m/s/s but off by a factor of 10.
A clarification of what units are actually being reported by the UM7 for the processed acceleration data would be appreciated.
Thanks,
Jason
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