A probehead of an NMR-MAS apparatus with a rotation axis (RA), which lies in an xz-plane, titled by an angle θ>0 relative to a z-axis. The angle θ is adjusted by tilting around a tilt axis (DA) parallel to the y-axis relative to a target angle θtarget. An angle measurement apparatus (9) has a first sensor element (7), which, together with a second sensor element (8) generates sensor signals dependent on the amplitude B0 of the static magnetic field and the vectorial orientation between the magnetic field B0 and a sensitivity vector. Two sensitivity vectors have an angle 5°<αi<175° to the z-axis and an angle β>10° to each other. The angle between the rotation axis and the z-axis can be measured precisely and reliably over a large range, providing a feedback signal for regulated adjustment or tracking of the angle θ.
