Calibration of an LSM303AGR accelerometer and magnetometer.

[@nikosar100]

I see a quite uniform distribution of your measurements. But the tripod does not allow positioning the probe very much below the “equator”. How did you manage?

[@nikos44317]

In fact I took measurements only above the “equator”, but I used eight different orientations of the sensor on the PVC tube in eight measurement sessions. At the start of each session, the PVC tube was horizontal and the sensor was attached to the tube in eight different ways: Axis Y pointing towards the head and away from the head and axis Z pointing up, down, left and right. The combinations are 2 * 4 = 8. In this way the sphere was covered and all the sensors were exposed to both positive and negative values of the measured stimuli. Nikos

[@nikosar100]

Hello 4:40 where did you find the arc cos formula? Thans

[@nikos44317]

Hello Have a look at the entry about the dot product in Wikipedia (en.wikipedia.org/wiki/Dot_product ). There are two definitions for the dot product of two vectors: --The geometric definition is A.B=||A||*||B||*cos(θ) (1) where ||A|| is the magnitude of A and θ is the angle between A and B. --The coordinate definition is A.B=Ax*Bx+Ay*By+Az*Bz (2) where Ax is the component of A along the axis X. From (1) we have that cos(θ)=Α.Β/(||Α||*||Β||). We substitute A.B according to (2) and we have cos(θ)=(Ax*Bx+Ay*By+Az*Bz)/(||Α||*||Β||). Also ||A||= square_root(Ax*Ax+Ay*Ay+Az*Az). Now that we know cos(θ), we can find θ by taking the inverse function arccos. Have a very nice day. Nikos