Good morning everybody,
I have a question about the accelerometer of the MPU9250, in the datasheet it is written that
When the device is placed on a flat surface, it will measure 0g on the X- and Y-axes and +1g on the Z-axis. The accelerometers’ scale factor is calibrated at the factory and is nominally independent of supply voltage.
But when I used it, the value are not equal to zero when I placed the chip on a flat surface. A certain offset exist, and when I do the norme of the gravity vector I didn't obtain 1g.
I did this calculation : ((Raw Value)/32767)*2
Here is an example of what I have obtain when I put the chip on a flat surface (X and Y should be 0g and Z should be 1g)
AccX : Raw = -1808 --> -0.11g
AccY : Raw = -14768 --> -0.90g
AccZ : Raw = -29788 --> -1.82g
Full gravity vector = 2.03g
After that I turn the sensor in order to have (Y and Z should be 0 and X should be 1g)
AccX : Raw = 15192 --> -0.93g
AccY : Raw = -15832 --> -0.97g
AccZ : Raw = -12208 --> -0.75g
Full gravity vector = 1.53g
And finally I turn the device in order to have (X and Z should 0 and Y should be 1g)
AccX : Raw = -828 --> -0.05g
AccY : Raw = -696 --> -0.04g
AccZ : Raw = -13704 --> -0.84g
Full gravity vector = 0.84g
I remarks that if I corrected value I can find right acceleration
AccX --> AccX[g]
AccY --> AccY[g] - 0.90g
AccZ --> AccZ[g] - 0.83g
It is a normal offset or do we need to do a special calibration ?
Thank you by advance for your response