OpenSense Knee Angle

[Hans-Jochen Edenhart]

Hello all,
I have written a Matlab script for calculating the knee angle out IMU data and quaternions.
for testing my script i put two sensors on a Goniometer.
at first i only moved the upper limb, then only the lower limb and at last both. Always to the same angle About 60 Degrees. i start my kneeangle at 180 Degrees.
my matlab script calculated Always the same angle.
i wanted to use open sense to validate my results.
but open sense has three different simulated angles.
do i use open sense not in the correct way? where is my mistake?
thanks for your help.
i added some screenshots to make my Problem more clearly