BNO055 calibration routine values

[LouisaG]

Hey everyone!

I'm working on a university project using BNO055 in order to come up with a filter algorithm for MEMS IMUs. I recorded some data while the chip lay exactly horizontal on the ground as to examine the remaining offsets after the calibration routine and found small offsets (~ 0.2 m/s^2). As I'm trying to find the "true" offset, I would like to get the raw, uncalibrated accelerations out of my data. I saved the calibration profile for each of my experiments, but I'm not sure as how to interpret the numbers given in the calibration profile. For example, I have  "calibrationData.accel_offset_x = -21", what does the -21 mean? Is it maybe bits in relation to the sensitivity given in the data sheet? 

Also, I was wondering if you could give my any more information about how the calibration algorithm in the firmware works exactly?

And, last but not least: Can you tell me how to interpret the "radius" parameter in the calibration profile?

Thanks in advance!

Louisa

[BSTRobin]

Hello LouisaG,

Ideally, the offset of the x-axis is 0. The actual output will be different from the ideal case, - 21 is the difference between and 0.

Usually, after the calibration is successful, read the profile and save it, and write the profile when necessary.

[LouisaG]

Hello BSTRRobin,

thanks for your answer. I'm aware that the actual output will never be the ideal value - that's why the sensors need calibration after all. Unfortunately, the screenshot from the manual doesn't help me with my problem. 

I've conducted several experiments with different calibration routines. Now I want to compare the data and the offsets from the experiments, therefore I need to know how to translate the offset values given in the calibration profile (e.g. -21) to values in m/s^2 for the accelerometer or deg/s for the gyro. Where can I find this conversion factor?

[BSTRobin]

Hello LouisaG,

You could see accel, gyro data conversion in BNO055 data sheet "3.6.4 Sensor calibration data".

Accel

Gyro